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Import Upstream version 0.27

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zhangyichun 2022-10-10 14:50:11 +08:00
commit 38c0eac41f
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use v5;
use strict;
use warnings;
use Module::Build;
use XS::Parse::Keyword::Builder;
my $build = Module::Build->new(
module_name => "Syntax::Keyword::Try",
test_requires => {
'Test::More' => '0.88', # done_testing
},
configure_requires => {
'Module::Build' => '0.4004', # test_requires
'XS::Parse::Keyword::Builder' => '0.06',
},
requires => {
'perl' => '5.014', # pluggable keywords, XOP
'XS::Parse::Keyword' => '0.06',
},
license => 'perl',
create_license => 1,
create_readme => 1,
meta_merge => {
resources => {
x_IRC => "irc://irc.perl.org/#io-async",
},
},
extra_compiler_flags => [qw( -Ihax )],
);
XS::Parse::Keyword::Builder->extend_module_build( $build );
$build->create_build_script;

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Revision history for Syntax-Keyword-Try
0.27 2022-02-22
[CHANGES]
* Updates to support Feature::Compat::Try 0.05 with new `finally {}`
blocks
0.26 2021-10-12
[CHANGES]
* Many internal updates to hax/ support files
[BUGFIXES]
* Fix try { return } to work correctly in all contexts without
upsetting -DDEBUGGING perls
0.25 2021-06-01
[CHANGES]
* Rewrite parsing logic to use XS::Parse::Keyword 0.06
* Removed the new-deprecated `try do { ... }` experimental syntax
* Updated docs now that 5.34 is officially released, including
`use feature 'try'`.
0.24 2021-05-10
[CHANGES]
* Deprecate the `try do { ... }` (experimental) syntax now that
try-in-do works reliably. It will be removed soon because it gets
in the way of converting the parser logic to XS::Parse::Keyword
* Add documentation about the core `use feature 'try'` and
Feature::Compat::Try module
* Added an initial attempt at B::Deparse logic
0.23 2021-03-27
[CHANGES]
* Unit tests and documentation of the handling of the final-value
semantics of `do { try ... }`
* Also mention core's `feature 'try'` in documentation
* Gives notice that the experimental 'try_value' feature is now
discouraged and will eventually be removed
0.22 2021-03-26
[CHANGES]
* Preserve wantarray context within the try {} block (RT133616)
* List-context `try do {}` now works fine as well
* Apply unit-testing for RT134790
0.21 2021-01-22
[CHANGES]
* Add some import configuration options required to make
Feature::Compat::Try work. Currently unit-tested but undocumented.
0.20 2020-11-24
[BUGFIXES]
* Fix for perl 5.14 by #include'ing hax/ files in the right order
0.19 2020-11-24
[CHANGES]
* Avoid the core Off() and Bit() macros as they were removed after
perl 5.33.3
* Support :experimental(try_value) to activate and silence the
warning
* Add documentation about the scalar context propagation issue of
RT124229
0.18 2020-08-01
[CHANGES]
* De-experiment the `catch ($var)` syntax
0.17 2020-07-31
[CHANGES]
* Ensure that `catch ($var)` does not retain exception value after
block exit
* Docs fixes for clarity on experimental status of `catch ($var)`
[BUGFIXES]
* Ensure sv_isa_sv is a macro for aTHX on threaded perls
0.16 2020-07-23
[CHANGES]
* Provide the `:experimental` import tag as a nicer way to silence
experimental warnings
[BUGFIXES]
* Don't name a variable `class` because it upsets some C compilers
(RT133043)
0.15 2020-07-21
[CHANGES]
* Experimental typed `catch (VAR ...)` conditions
0.14 2020-07-07
[CHANGES]
* Optional experimental syntax of `catch (VAR)` instead of previous
experimental `catch my VAR`
* Mark `catch my VAR` as deprecated
* Added explicit use VERSION declarations to every perl file
0.13 2020-06-29
[BUGFIXES]
* Pack correct MANIFEST to include hax/ files
0.12 2020-06-29
[CHANGES]
* Optional and experimental allocation of a new lexical under
`catch my $VAR` syntax (RT130702). However, this syntax may not
survive long, as part of the ongoing typed catch design work.
[BUGFIXES]
* Work around perl versions prior to 5.22 built with -DDEBUGGING
getting upset about new*OP() being invoked with OP_CUSTOM
(RT128562)
0.11 2019-09-07
[CHANGES]
* Use wrap_keyword_plugin() instead of direct access to
PL_keyword_plugin
[BUGFIXES]
* Build OP_ENTER/OP_LEAVE structure the correct way so perl 5.31.3
doesn't crash
* Fix OP_NEXT/OP_LAST/OP_REDO mangling for perl 5.31.3 to avoid
CPU spin (RT129975)
0.10 2019-06-13
[CHANGES]
* Added experimental value-semantic expression form (RT121267)
* Document that the module works nicely with Future::AsyncAwait
* Ignore import symbols `catch` and `finally`
[BUGFIXES]
* Fixed spelling mistakes in documentation (patch from debian)
(RT124140)
0.09 2017-11-08 14:33:19
[BUGFIXES]
* Make module loading thread-safe on perls 5.16 and above. (RT123547)
Safety on perl 5.14 is still an unsolved problem.
0.08 2017-09-14 17:26:20
[BUGFIXES]
* Handle the OpSIBLING of an OP_{NEXT,LAST,REDO} correctly (RT123040)
0.07 2017-08-13 23:11:39
[CHANGES]
* Capture 80await+try.t unit test from Future-AsyncAwait
* Improved implementation of OP_PUSHFINALLY to help make try/finally
inside async/await subs work
[BUGFIXES]
* Make 'eval { try { return ... } }' work correctly
* Make 'return LIST' inside try{} blocks work correctly (RT122795)
- with thanks to Zefram for code inspiration
0.06 2017/06/06 14:59:30
[CHANGES]
* Clarify documentation about the behaviour of try {} blocks without
catch {}; include comparison with other modules
[BUGFIXES]
* Fix typo in #ifdef test (RT119709)
* Restore C89 compatibility again (RT119665)
0.05 2017/06/05 14:04:06
[CHANGES]
* Add a SEE ALSO link pointing at the value-semantics RT ticket
[BUGFIXES]
* Fix cLISTOP->op_last field to keep DEBUGGING builds happy
(RT119095)
0.04 2016/11/25 15:06:18
[CHANGES]
* Removed stale documentation about now-fixed warnings from
next/last/redo
[BUGFIXES]
* Fix C code for C89 compatibility (RT118950)
* Localise $@ around try/catch (RT118415)
0.03 2016/11/24 10:27:45
[CHANGES]
* Default import of 'try' keyword
* Suppress 'exiting' warning around next/last/redo inside a try block
* Don't bother outputting a Makefile.PL
0.02 2016/09/06 21:29:25
[BUGFIXES]
* Use OpSIBLING() macro for compatibility for perl 5.25.x
* Documentation fixes
0.01 2016/09/05 22:19:33
First version, released on an unsuspecting world.

379
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This software is copyright (c) 2022 by Paul Evans <leonerd@leonerd.org.uk>.
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.
Terms of the Perl programming language system itself
a) the GNU General Public License as published by the Free
Software Foundation; either version 1, or (at your option) any
later version, or
b) the "Artistic License"
--- The GNU General Public License, Version 1, February 1989 ---
This software is Copyright (c) 2022 by Paul Evans <leonerd@leonerd.org.uk>.
This is free software, licensed under:
The GNU General Public License, Version 1, February 1989
GNU GENERAL PUBLIC LICENSE
Version 1, February 1989
Copyright (C) 1989 Free Software Foundation, Inc.
51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
Preamble
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--- The Artistic License 1.0 ---
This software is Copyright (c) 2022 by Paul Evans <leonerd@leonerd.org.uk>.
This is free software, licensed under:
The Artistic License 1.0
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The End

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Build.PL
Changes
hax/newOP_CUSTOM.c.inc
hax/op_sibling_splice.c.inc
hax/optree-additions.c.inc
hax/perl-additions.c.inc
hax/perl-backcompat.c.inc
lib/Syntax/Keyword/Try.pm
lib/Syntax/Keyword/Try.xs
lib/Syntax/Keyword/Try/Deparse.pm
MANIFEST This list of files
t/00use.t
t/01trycatch.t
t/02tryfinally.t
t/03trycatchfinally.t
t/04catch-types.t
t/10snail.t
t/11loop.t
t/12return.t
t/13die-in-finally.t
t/14try-localises.t
t/15context.t
t/16final-expr.t
t/30compat.t
t/70deparse.t
t/80await+SKT.t
t/80defer+SKT.t
t/90rt123547.t
t/90rt125971.t
t/99pod.t
README
LICENSE
META.yml
META.json

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{
"abstract" : "a C<try/catch/finally> syntax for perl",
"author" : [
"Paul Evans <leonerd@leonerd.org.uk>"
],
"dynamic_config" : 1,
"generated_by" : "Module::Build version 0.4231",
"license" : [
"perl_5"
],
"meta-spec" : {
"url" : "http://search.cpan.org/perldoc?CPAN::Meta::Spec",
"version" : 2
},
"name" : "Syntax-Keyword-Try",
"prereqs" : {
"build" : {
"requires" : {
"ExtUtils::CBuilder" : "0"
}
},
"configure" : {
"requires" : {
"Module::Build" : "0.4004",
"XS::Parse::Keyword::Builder" : "0.06"
}
},
"runtime" : {
"requires" : {
"XS::Parse::Keyword" : "0.06",
"perl" : "5.014"
}
},
"test" : {
"requires" : {
"Test::More" : "0.88"
}
}
},
"provides" : {
"Syntax::Keyword::Try" : {
"file" : "lib/Syntax/Keyword/Try.pm",
"version" : "0.27"
},
"Syntax::Keyword::Try::Deparse" : {
"file" : "lib/Syntax/Keyword/Try/Deparse.pm",
"version" : "0.27"
}
},
"release_status" : "stable",
"resources" : {
"license" : [
"http://dev.perl.org/licenses/"
],
"x_IRC" : "irc://irc.perl.org/#io-async"
},
"version" : "0.27",
"x_serialization_backend" : "JSON::PP version 4.06"
}

32
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---
abstract: 'a C<try/catch/finally> syntax for perl'
author:
- 'Paul Evans <leonerd@leonerd.org.uk>'
build_requires:
ExtUtils::CBuilder: '0'
Test::More: '0.88'
configure_requires:
Module::Build: '0.4004'
XS::Parse::Keyword::Builder: '0.06'
dynamic_config: 1
generated_by: 'Module::Build version 0.4231, CPAN::Meta::Converter version 2.150010'
license: perl
meta-spec:
url: http://module-build.sourceforge.net/META-spec-v1.4.html
version: '1.4'
name: Syntax-Keyword-Try
provides:
Syntax::Keyword::Try:
file: lib/Syntax/Keyword/Try.pm
version: '0.27'
Syntax::Keyword::Try::Deparse:
file: lib/Syntax/Keyword/Try/Deparse.pm
version: '0.27'
requires:
XS::Parse::Keyword: '0.06'
perl: '5.014'
resources:
IRC: irc://irc.perl.org/#io-async
license: http://dev.perl.org/licenses/
version: '0.27'
x_serialization_backend: 'CPAN::Meta::YAML version 0.018'

398
README Normal file
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NAME
Syntax::Keyword::Try - a try/catch/finally syntax for perl
SYNOPSIS
use Syntax::Keyword::Try;
sub foo {
try {
attempt_a_thing();
return "success";
}
catch ($e) {
warn "It failed - $e";
return "failure";
}
}
DESCRIPTION
This module provides a syntax plugin that implements exception-handling
semantics in a form familiar to users of other languages, being built
on a block labeled with the try keyword, followed by at least one of a
catch or finally block.
As well as providing a handy syntax for this useful behaviour, this
module also serves to contain a number of code examples for how to
implement parser plugins and manipulate optrees to provide new syntax
and behaviours for perl code.
Syntax similar to this module has now been added to core perl, starting
at version 5.34.0. If you are writing new code, it is suggested that
you instead use the Feature::Compat::Try module instead, as that will
enable the core feature on those supported perl versions, falling back
to Syntax::Keyword::Try on older perls.
Experimental Features
Some of the features of this module are currently marked as
experimental. They will provoke warnings in the experimental category,
unless silenced.
You can silence this with no warnings 'experimental' but then that will
silence every experimental warning, which may hide others
unintentionally. For a more fine-grained approach you can instead use
the import line for this module to only silence this module's warnings
selectively:
use Syntax::Keyword::Try qw( try :experimental(typed) );
use Syntax::Keyword::Try qw( try :experimental ); # all of the above
Don't forget to import the main try symbol itself, to activate the
syntax.
KEYWORDS
try
try {
STATEMENTS...
}
...
A try statement provides the main body of code that will be invoked,
and must be followed by either a catch statement, a finally statement,
or both.
Execution of the try statement itself begins from the block given to
the statement and continues until either it throws an exception, or
completes successfully by reaching the end of the block. What will
happen next depends on the presence of a catch or finally statement
immediately following it.
The body of a try {} block may contain a return expression. If
executed, such an expression will cause the entire containing function
to return with the value provided. This is different from a plain eval
{} block, in which circumstance only the eval itself would return, not
the entire function.
The body of a try {} block may contain loop control expressions (redo,
next, last) which will have their usual effect on any loops that the
try {} block is contained by.
The parsing rules for the set of statements (the try block and its
associated catch and finally) are such that they are parsed as a self-
contained statement. Because of this, there is no need to end with a
terminating semicolon.
Even though it parses as a statement and not an expression, a try block
can still yield a value if it appears as the final statement in its
containing sub or do block. For example:
my $result = do {
try { attempt_func() }
catch ($e) { "Fallback Value" }
};
Note (especially to users of Try::Tiny and similar) that the try {}
block itself does not necessarily stop exceptions thrown inside it from
propagating outside. It is the presence of a later catch {} block which
causes this to happen. A try with only a finally and no catch will
still propagate exceptions up to callers as normal.
catch
...
catch ($var) {
STATEMENTS...
}
or
...
catch {
STATEMENTS...
}
A catch statement provides a block of code to the preceding try
statement that will be invoked in the case that the main block of code
throws an exception. Optionally a new lexical variable can be provided
to store the exception in. If not provided, the catch block can inspect
the raised exception by looking in $@ instead.
Presence of this catch statement causes any exception thrown by the
preceding try block to be non-fatal to the surrounding code. If the
catch block wishes to optionally handle some exceptions but not others,
it can re-raise it (or another exception) by calling die in the usual
manner.
As with try, the body of a catch {} block may also contain a return
expression, which as before, has its usual meaning, causing the entire
containing function to return with the given value. The body may also
contain loop control expressions (redo, next or last) which also have
their usual effect.
If a catch statement is not given, then any exceptions raised by the
try block are raised to the caller in the usual way.
catch (Typed)
...
catch ($var isa Class) { ... }
...
catch ($var =~ m/^Regexp match/) { ... }
Experimental; since version 0.15.
Optionally, multiple catch statements can be provided, where each block
is given a guarding condition, to control whether or not it will catch
particular exception values. Use of this syntax will provoke an
experimental category warning on supporting perl versions, unless
silenced by importing the :experimental(typed) tag (see above).
Two kinds of condition are supported:
*
catch ($var isa Class)
The block is invoked only if the caught exception is a blessed
object, and derives from the given package name.
On Perl version 5.32 onwards, this condition test is implemented
using the same op type that the core $var isa Class syntax is
provided by and works in exactly the same way.
On older perl versions it is emulated by a compatibility function.
Currently this function does not respect a ->isa method overload on
the exception instance. Usually this should not be a problem, as
exception class types rarely provide such a method.
*
catch ($var =~ m/regexp/)
The block is invoked only if the caught exception is a string that
matches the given regexp.
When an exception is caught, each condition is tested in the order they
are written in, until a matching case is found. If such a case is found
the corresponding block is invoked, and no further condition is tested.
If no contional block matched and there is a default (unconditional)
block at the end then that is invoked instead. If no such block exists,
then the exception is propagated up to the calling scope.
finally
...
finally {
STATEMENTS...
}
A finally statement provides a block of code to the preceding try
statement (or try/catch pair) which is executed afterwards, both in the
case of a normal execution or a thrown exception. This code block may
be used to provide whatever clean-up operations might be required by
preceding code.
Because it is executed during a stack cleanup operation, a finally {}
block may not cause the containing function to return, or to alter the
return value of it. It also cannot see the containing function's @_
arguments array (though as it is block scoped within the function, it
will continue to share any normal lexical variables declared up until
that point). It is protected from disturbing the value of $@. If the
finally {} block code throws an exception, this will be printed as a
warning and discarded, leaving $@ containing the original exception, if
one existed.
OTHER MODULES
There are already quite a number of modules on CPAN that provide a
try/catch-like syntax for Perl.
* Try
* TryCatch
* Try::Tiny
* Syntax::Feature::Try
In addition, core perl itself gained a try/catch syntax based on this
module at version 5.34.0. It is available as use feature 'try'.
They are compared here, by feature:
True syntax plugin
Like Try and Syntax::Feature::Try, this module is implemented as a true
syntax plugin, allowing it to provide new parsing rules not available
to simple functions. Most notably here it means that the resulting
combination does not need to end in a semicolon.
The core feature 'try' is also implemented as true native syntax in the
perl parser.
In comparison, Try::Tiny is plain perl and provides its functionality
using regular perl functions; as such its syntax requires the trailing
semicolon.
TryCatch is a hybrid that uses Devel::Declare to parse the syntax tree.
@_ in a try or catch block
Because the try and catch block code is contained in a true block
rather than an entire anonymous subroutine, invoking it does not
interfere with the @_ arguments array. Code inside these blocks can
interact with the containing function's array as before.
This feature is unique among these modules; none of the others listed
have this ability.
The core feature 'try' also behaves in this manner.
return in a try or catch block
Like TryCatch and Syntax::Feature::Try, the return statement has its
usual effect within a subroutine containing syntax provided by this
module. Namely, it causes the containing sub itself to return.
It also behaves this way using the core feature 'try'.
In comparison, using Try or Try::Tiny mean that a return statement will
only exit from the try block.
next/last/redo in a try or catch block
The loop control keywords of next, last and redo have their usual
effect on dynamically contained loops.
These also work fine when using the core feature 'try'.
Syntax::Feature::Try documents that these do not work there. The other
modules make no statement either way.
Value Semantics
Like Try and Syntax::Feature::Try, the syntax provided by this module
only works as a syntax-level statement and not an expression. You
cannot assign from the result of a try block. A common workaround is to
wrap the try/catch statement inside a do block, where its final
expression can be captured and used as a value.
The same do block wrapping also works for the core feature 'try'.
In comparison, the behaviour implemented by Try::Tiny can be used as a
valued expression, such as assigned to a variable or returned to the
caller of its containing function.
try without catch
Like Syntax::Feature::Try, the syntax provided by this module allows a
try block to be followed by only a finally block, with no catch. In
this case, exceptions thrown by code contained by the try are not
suppressed, instead they propagate as normal to callers. This matches
the behaviour familiar to Java or C++ programmers.
In comparison, the code provided by Try and Try::Tiny always suppress
exception propagation even without an actual catch block.
The TryCatch module does not allow a try block not followed by catch.
The core feature 'try' does not implement finally at all, and also
requires that every try block be followed by a catch.
Typed catch
Try and Try::Tiny make no attempt to perform any kind of typed dispatch
to distinguish kinds of exception caught by catch blocks.
Likewise the core feature 'try' currently does not provide this
ability, though it remains an area of ongoing design work.
TryCatch and Syntax::Feature::Try both attempt to provide a kind of
typed dispatch where different classes of exception are caught by
different blocks of code, or propagated up entirely to callers.
This module provides such an ability, via the currently-experimental
catch (VAR cond...) syntax.
The design thoughts continue on the RT ticket
https://rt.cpan.org/Ticket/Display.html?id=123918.
WITH OTHER MODULES
Future::AsyncAwait
As of Future::AsyncAwait version 0.10 and Syntax::Keyword::Try version
0.07, cross-module integration tests assert that basic try/catch blocks
inside an async sub work correctly, including those that attempt to
return from inside try.
use Future::AsyncAwait;
use Syntax::Keyword::Try;
async sub attempt
{
try {
await func();
return "success";
}
catch {
return "failed";
}
}
ISSUES
Thread-safety at load time cannot be assured before perl 5.16
On perl versions 5.16 and above this module is thread-safe.
On perl version 5.14 this module is thread-safe provided that it is
used before any additional threads are created.
However, when using 5.14 there is a race condition if this module is
loaded late in the program startup, after additional threads have been
created. This leads to the potential for it to be started up multiple
times concurrently, which creates data races when modifying internal
structures and likely leads to a segmentation fault, either during load
or soon after when more code is compiled.
As a workaround, for any such program that creates multiple threads,
loads additional code (such as dynamically-discovered plugins), and has
to run on 5.14, it should make sure to
use Syntax::Keyword::Try;
early on in startup, before it spins out any additional threads.
(See also https://rt.cpan.org/Public/Bug/Display.html?id=123547)
$@ is not local'ised by try do before perl 5.24
On perl versions 5.24 and above, or when using only control-flow
statement syntax, $@ is always correctly localised.
However, when using the experimental value-yielding expression version
try do {...} on perl versions 5.22 or older, the localisation of $@
does not correctly apply around the expression. After such an
expression, the value of $@ will leak out if a failure happened and the
catch block was invoked, overwriting any previous value that was
visible there.
(See also https://rt.cpan.org/Public/Bug/Display.html?id=124366)
ACKNOWLEDGEMENTS
With thanks to Zefram, ilmari and others from irc.perl.org/#p5p for
assisting with trickier bits of XS logic.
AUTHOR
Paul Evans <leonerd@leonerd.org.uk>

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/* vi: set ft=c : */
/* Before perl 5.22 under -DDEBUGGING, various new*OP() functions throw assert
* failures on OP_CUSTOM.
* https://rt.cpan.org/Ticket/Display.html?id=128562
*/
#define newOP_CUSTOM(func, flags) S_newOP_CUSTOM(aTHX_ func, flags)
#define newUNOP_CUSTOM(func, flags, first) S_newUNOP_CUSTOM(aTHX_ func, flags, first)
#define newSVOP_CUSTOM(func, flags, sv) S_newSVOP_CUSTOM(aTHX_ func, flags, sv)
#define newBINOP_CUSTOM(func, flags, first, last) S_newBINOP_CUSTOM(aTHX_ func, flags, first, last)
#define newLOGOP_CUSTOM(func, flags, first, other) S_newLOGOP_CUSTOM(aTHX_ func, flags, first, other)
static OP *S_newOP_CUSTOM(pTHX_ OP *(*func)(pTHX), U32 flags)
{
OP *op = newOP(OP_CUSTOM, flags);
op->op_ppaddr = func;
return op;
}
static OP *S_newUNOP_CUSTOM(pTHX_ OP *(*func)(pTHX), U32 flags, OP *first)
{
UNOP *unop;
#if HAVE_PERL_VERSION(5,22,0)
unop = (UNOP *)newUNOP(OP_CUSTOM, flags, first);
#else
NewOp(1101, unop, 1, UNOP);
unop->op_type = (OPCODE)OP_CUSTOM;
unop->op_first = first;
unop->op_flags = (U8)(flags | OPf_KIDS);
unop->op_private = (U8)(1 | (flags >> 8));
#endif
unop->op_ppaddr = func;
return (OP *)unop;
}
static OP *S_newSVOP_CUSTOM(pTHX_ OP *(*func)(pTHX), U32 flags, SV *sv)
{
SVOP *svop;
#if HAVE_PERL_VERSION(5,22,0)
svop = (SVOP *)newSVOP(OP_CUSTOM, flags, sv);
#else
NewOp(1101, svop, 1, SVOP);
svop->op_type = (OPCODE)OP_CUSTOM;
svop->op_sv = sv;
svop->op_next = (OP *)svop;
svop->op_flags = 0;
svop->op_private = 0;
#endif
svop->op_ppaddr = func;
return (OP *)svop;
}
static OP *S_newBINOP_CUSTOM(pTHX_ OP *(*func)(pTHX), U32 flags, OP *first, OP *last)
{
BINOP *binop;
#if HAVE_PERL_VERSION(5,22,0)
binop = (BINOP *)newBINOP(OP_CUSTOM, flags, first, last);
#else
NewOp(1101, binop, 1, BINOP);
binop->op_type = (OPCODE)OP_CUSTOM;
binop->op_first = first;
first->op_sibling = last;
binop->op_last = last;
binop->op_flags = (U8)(flags | OPf_KIDS);
binop->op_private = (U8)(2 | (flags >> 8));
#endif
binop->op_ppaddr = func;
return (OP *)binop;
}
static OP *S_newLOGOP_CUSTOM(pTHX_ OP *(*func)(pTHX), U32 flags, OP *first, OP *other)
{
OP *o;
#if HAVE_PERL_VERSION(5,22,0)
o = newLOGOP(OP_CUSTOM, flags, first, other);
#else
/* Parts of this code copypasted from perl 5.20.0's op.c S_new_logop()
*/
LOGOP *logop;
first = op_contextualize(first, G_SCALAR);
NewOp(1101, logop, 1, LOGOP);
logop->op_type = (OPCODE)OP_CUSTOM;
logop->op_ppaddr = NULL; /* Because caller only overrides it anyway */
logop->op_first = first;
logop->op_flags = (U8)(flags | OPf_KIDS);
logop->op_other = LINKLIST(other);
/* logop->op_private has nothing interesting for OP_CUSTOM */
/* Link in postfix order */
logop->op_next = LINKLIST(first);
first->op_next = (OP *)logop;
first->op_sibling = other;
/* No CHECKOP for OP_CUSTOM */
o = newUNOP(OP_NULL, 0, (OP *)logop);
other->op_next = o;
#endif
/* the returned op is actually an UNOP that's either NULL or NOT; the real
* logop is the op_next of it
*/
cUNOPx(o)->op_first->op_ppaddr = func;
return o;
}

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/* vi: set ft=c : */
#ifndef op_sibling_splice
# define op_sibling_splice(parent, start, del_count, insert) S_op_sibling_splice(aTHX_ parent, start, del_count, insert)
static OP *S_op_sibling_splice(pTHX_ OP *parent, OP *start, int del_count, OP *insert)
{
OP *deleted = NULL;
if(!insert && !del_count)
return NULL;
OP **prevp;
if(start)
prevp = &(start->op_sibling);
else
prevp = &(cLISTOPx(parent)->op_first);
OP *after = *prevp;
if(del_count) {
croak("Back-compat op_sibling_splice with del_count != 0 not yet implemented");
/* THIS IS AS YET UNTESTED
deleted = *prevp;
OP *o = deleted;
while(del_count > 1)
o = o->op_sibling, del_count--;
after = o->op_sibling;
o->op_sibling = NULL;
*/
}
if(insert) {
*prevp = insert;
OP *o = insert;
while(o->op_sibling)
o = o->op_sibling;
o->op_sibling = after;
}
else
*prevp = after;
return deleted;
}
#endif

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/* vi: set ft=c : */
#define newAELEMOP(flags, first, key) S_newAELEMOP(aTHX_ flags, first, key)
static OP *S_newAELEMOP(pTHX_ U32 flags, OP *first, I32 key)
{
#if HAVE_PERL_VERSION(5,16,0)
if(key >= -128 && key < 128 && first->op_type == OP_PADAV) {
OP *o = newOP(OP_AELEMFAST_LEX, flags);
o->op_private = (I8)key;
o->op_targ = first->op_targ;
op_free(first);
return o;
}
#endif
return newBINOP(OP_AELEM, flags, first, newSVOP(OP_CONST, 0, newSViv(key)));
}
#define newPADxVOP(type, padix, flags, private) S_newPADxVOP(aTHX_ type, padix, flags, private)
static OP *S_newPADxVOP(pTHX_ I32 type, PADOFFSET padix, I32 flags, U32 private)
{
OP *op = newOP(type, flags);
op->op_targ = padix;
op->op_private = private;
return op;
}
#if HAVE_PERL_VERSION(5, 22, 0)
# define HAVE_UNOP_AUX
#endif
#ifndef HAVE_UNOP_AUX
typedef struct UNOP_with_IV {
UNOP baseop;
IV iv;
} UNOP_with_IV;
#define newUNOP_with_IV(type, flags, first, iv) S_newUNOP_with_IV(aTHX_ type, flags, first, iv)
static OP *S_newUNOP_with_IV(pTHX_ I32 type, I32 flags, OP *first, IV iv)
{
/* Cargoculted from perl's op.c:Perl_newUNOP()
*/
UNOP_with_IV *op = PerlMemShared_malloc(sizeof(UNOP_with_IV) * 1);
NewOp(1101, op, 1, UNOP_with_IV);
if(!first)
first = newOP(OP_STUB, 0);
UNOP *unop = (UNOP *)op;
unop->op_type = (OPCODE)type;
unop->op_first = first;
unop->op_ppaddr = NULL;
unop->op_flags = (U8)flags | OPf_KIDS;
unop->op_private = (U8)(1 | (flags >> 8));
op->iv = iv;
return (OP *)op;
}
#endif
#define newMETHOD_REDIR_OP(rclass, methname, flags) S_newMETHOD_REDIR_OP(aTHX_ rclass, methname, flags)
static OP *S_newMETHOD_REDIR_OP(pTHX_ SV *rclass, SV *methname, I32 flags)
{
#if HAVE_PERL_VERSION(5, 22, 0)
OP *op = newMETHOP_named(OP_METHOD_REDIR, flags, methname);
# ifdef USE_ITHREADS
{
/* cargoculted from S_op_relocate_sv() */
PADOFFSET ix = pad_alloc(OP_CONST, SVf_READONLY);
PAD_SETSV(ix, rclass);
cMETHOPx(op)->op_rclass_targ = ix;
}
# else
cMETHOPx(op)->op_rclass_sv = rclass;
# endif
#else
OP *op = newUNOP(OP_METHOD, flags,
newSVOP(OP_CONST, 0, newSVpvf("%" SVf "::%" SVf, rclass, methname)));
#endif
return op;
}

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/* vi: set ft=c : */
#ifndef av_count
# define av_count(av) (AvFILL(av) + 1)
#endif
#if HAVE_PERL_VERSION(5, 22, 0)
# define PadnameIsNULL(pn) (!(pn))
#else
# define PadnameIsNULL(pn) (!(pn) || (pn) == &PL_sv_undef)
#endif
#ifndef hv_deletes
# define hv_deletes(hv, skey, flags) hv_delete((hv), ("" skey ""), (sizeof(skey) - 1), flags)
#endif
#if HAVE_PERL_VERSION(5, 22, 0)
# define PadnameOUTER_off(pn) (PadnameFLAGS(pn) &= ~PADNAMEt_OUTER)
#else
/* PadnameOUTER is really the SvFAKE flag */
# define PadnameOUTER_off(pn) SvFAKE_off(pn)
#endif
#define save_strndup(s, l) S_save_strndup(aTHX_ s, l)
static char *S_save_strndup(pTHX_ char *s, STRLEN l)
{
/* savepvn doesn't put anything on the save stack, despite its name */
char *ret = savepvn(s, l);
SAVEFREEPV(ret);
return ret;
}
#define sv_setrv(s, r) S_sv_setrv(aTHX_ s, r)
static void S_sv_setrv(pTHX_ SV *sv, SV *rv)
{
sv_setiv(sv, (IV)rv);
#if !HAVE_PERL_VERSION(5, 24, 0)
SvIOK_off(sv);
#endif
SvROK_on(sv);
}
static char *PL_savetype_name[] PERL_UNUSED_DECL = {
/* These have been present since 5.16 */
[SAVEt_ADELETE] = "ADELETE",
[SAVEt_AELEM] = "AELEM",
[SAVEt_ALLOC] = "ALLOC",
[SAVEt_APTR] = "APTR",
[SAVEt_AV] = "AV",
[SAVEt_BOOL] = "BOOL",
[SAVEt_CLEARSV] = "CLEARSV",
[SAVEt_COMPILE_WARNINGS] = "COMPILE_WARNINGS",
[SAVEt_COMPPAD] = "COMPPAD",
[SAVEt_DELETE] = "DELETE",
[SAVEt_DESTRUCTOR] = "DESTRUCTOR",
[SAVEt_DESTRUCTOR_X] = "DESTRUCTOR_X",
[SAVEt_FREECOPHH] = "FREECOPHH",
[SAVEt_FREEOP] = "FREEOP",
[SAVEt_FREEPV] = "FREEPV",
[SAVEt_FREESV] = "FREESV",
[SAVEt_GENERIC_PVREF] = "GENERIC_PVREF",
[SAVEt_GENERIC_SVREF] = "GENERIC_SVREF",
[SAVEt_GP] = "GP",
[SAVEt_GVSV] = "GVSV",
[SAVEt_HELEM] = "HELEM",
[SAVEt_HINTS] = "HINTS",
[SAVEt_HPTR] = "HPTR",
[SAVEt_HV] = "HV",
[SAVEt_I16] = "I16",
[SAVEt_I32] = "I32",
[SAVEt_I32_SMALL] = "I32_SMALL",
[SAVEt_I8] = "I8",
[SAVEt_INT] = "INT",
[SAVEt_INT_SMALL] = "INT_SMALL",
[SAVEt_ITEM] = "ITEM",
[SAVEt_IV] = "IV",
[SAVEt_LONG] = "LONG",
[SAVEt_MORTALIZESV] = "MORTALIZESV",
[SAVEt_NSTAB] = "NSTAB",
[SAVEt_OP] = "OP",
[SAVEt_PADSV_AND_MORTALIZE] = "PADSV_AND_MORTALIZE",
[SAVEt_PARSER] = "PARSER",
[SAVEt_PPTR] = "PPTR",
[SAVEt_REGCONTEXT] = "REGCONTEXT",
[SAVEt_SAVESWITCHSTACK] = "SAVESWITCHSTACK",
[SAVEt_SET_SVFLAGS] = "SET_SVFLAGS",
[SAVEt_SHARED_PVREF] = "SHARED_PVREF",
[SAVEt_SPTR] = "SPTR",
[SAVEt_STACK_POS] = "STACK_POS",
[SAVEt_SVREF] = "SVREF",
[SAVEt_SV] = "SV",
[SAVEt_VPTR] = "VPTR",
#if HAVE_PERL_VERSION(5,18,0)
[SAVEt_CLEARPADRANGE] = "CLEARPADRANGE",
[SAVEt_GVSLOT] = "GVSLOT",
#endif
#if HAVE_PERL_VERSION(5,20,0)
[SAVEt_READONLY_OFF] = "READONLY_OFF",
[SAVEt_STRLEN] = "STRLEN",
#endif
#if HAVE_PERL_VERSION(5,22,0)
[SAVEt_FREEPADNAME] = "FREEPADNAME",
#endif
#if HAVE_PERL_VERSION(5,24,0)
[SAVEt_TMPSFLOOR] = "TMPSFLOOR",
#endif
#if HAVE_PERL_VERSION(5,34,0)
[SAVEt_STRLEN_SMALL] = "STRLEN_SMALL",
[SAVEt_HINTS_HH] = "HINTS_HH",
#endif
};
#define dKWARG(count) \
U32 kwargi = count; \
U32 kwarg; \
SV *kwval; \
/* TODO: complain about odd number of args */
#define KWARG_NEXT(args) \
S_kwarg_next(aTHX_ args, &kwargi, items, ax, &kwarg, &kwval)
static bool S_kwarg_next(pTHX_ const char *args[], U32 *kwargi, U32 argc, U32 ax, U32 *kwarg, SV **kwval)
{
if(*kwargi >= argc)
return FALSE;
SV *argname = ST(*kwargi); (*kwargi)++;
if(!SvOK(argname))
croak("Expected string for next argument name, got undef");
*kwarg = 0;
while(args[*kwarg]) {
if(strEQ(SvPV_nolen(argname), args[*kwarg])) {
*kwval = ST(*kwargi); (*kwargi)++;
return TRUE;
}
(*kwarg)++;
}
croak("Unrecognised argument name '%" SVf "'", SVfARG(argname));
}
#define import_pragma(pragma, arg) S_import_pragma(aTHX_ pragma, arg)
static void S_import_pragma(pTHX_ const char *pragma, const char *arg)
{
dSP;
bool unimport = FALSE;
if(pragma[0] == '-') {
unimport = TRUE;
pragma++;
}
SAVETMPS;
EXTEND(SP, 2);
PUSHMARK(SP);
mPUSHp(pragma, strlen(pragma));
if(arg)
mPUSHp(arg, strlen(arg));
PUTBACK;
call_method(unimport ? "unimport" : "import", G_VOID);
FREETMPS;
}
#define ensure_module_version(module, version) S_ensure_module_version(aTHX_ module, version)
static void S_ensure_module_version(pTHX_ SV *module, SV *version)
{
dSP;
ENTER;
PUSHMARK(SP);
PUSHs(module);
PUSHs(version);
PUTBACK;
call_method("VERSION", G_VOID);
LEAVE;
}
#if HAVE_PERL_VERSION(5, 16, 0)
/* TODO: perl 5.14 lacks HvNAMEUTF8, gv_fetchmeth_pvn() */
# define fetch_superclass_method_pv(stash, pv, len, level) S_fetch_superclass_method_pv(aTHX_ stash, pv, len, level)
static CV *S_fetch_superclass_method_pv(pTHX_ HV *stash, const char *pv, STRLEN len, U32 level)
{
# if HAVE_PERL_VERSION(5, 18, 0)
GV *gv = gv_fetchmeth_pvn(stash, pv, len, level, GV_SUPER);
# else
SV *superclassname = newSVpvf("%*s::SUPER", HvNAMELEN_get(stash), HvNAME_get(stash));
if(HvNAMEUTF8(stash))
SvUTF8_on(superclassname);
SAVEFREESV(superclassname);
HV *superstash = gv_stashsv(superclassname, GV_ADD);
GV *gv = gv_fetchmeth_pvn(superstash, pv, len, level, 0);
# endif
if(!gv)
return NULL;
return GvCV(gv);
}
#endif /* HAVE_PERL_VERSION(5, 16, 0) */
#define get_class_isa(stash) S_get_class_isa(aTHX_ stash)
static AV *S_get_class_isa(pTHX_ HV *stash)
{
GV **gvp = (GV **)hv_fetchs(stash, "ISA", 0);
if(!gvp || !GvAV(*gvp))
croak("Expected %s to have a @ISA list", HvNAME(stash));
return GvAV(*gvp);
}
#define find_cop_for_lvintro(padix, o, copp) S_find_cop_for_lvintro(aTHX_ padix, o, copp)
static COP *S_find_cop_for_lvintro(pTHX_ PADOFFSET padix, OP *o, COP **copp)
{
for( ; o; o = OpSIBLING(o)) {
if(OP_CLASS(o) == OA_COP) {
*copp = (COP *)o;
}
else if(o->op_type == OP_PADSV && o->op_targ == padix && o->op_private & OPpLVAL_INTRO) {
return *copp;
}
else if(o->op_flags & OPf_KIDS) {
COP *ret = find_cop_for_lvintro(padix, cUNOPx(o)->op_first, copp);
if(ret)
return ret;
}
}
return NULL;
}
#define lex_consume_unichar(c) MY_lex_consume_unichar(aTHX_ c)
static bool MY_lex_consume_unichar(pTHX_ U32 c)
{
if(lex_peek_unichar(0) != c)
return FALSE;
lex_read_unichar(0);
return TRUE;
}
#if HAVE_PERL_VERSION(5, 16, 0)
/* TODO: perl 5.14 lacks HvNAMEUTF8, HvNAMELEN, sv_derived_from_pvn */
# define sv_derived_from_hv(sv, hv) MY_sv_derived_from_hv(aTHX_ sv, hv)
static bool MY_sv_derived_from_hv(pTHX_ SV *sv, HV *hv)
{
char *hvname = HvNAME(hv);
if(!hvname)
return FALSE;
return sv_derived_from_pvn(sv, hvname, HvNAMELEN(hv), HvNAMEUTF8(hv) ? SVf_UTF8 : 0);
}
#endif /* HAVE_PERL_VERSION(5, 16, 0) */

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/* vi: set ft=c : */
#define HAVE_PERL_VERSION(R, V, S) \
(PERL_REVISION > (R) || (PERL_REVISION == (R) && (PERL_VERSION > (V) || (PERL_VERSION == (V) && (PERL_SUBVERSION >= (S))))))
#ifndef NOT_REACHED
# define NOT_REACHED assert(0)
#endif
#ifndef SvTRUE_NN
# define SvTRUE_NN(sv) SvTRUE(sv)
#endif
#ifndef G_LIST
# define G_LIST G_ARRAY
#endif
#if !HAVE_PERL_VERSION(5, 18, 0)
typedef AV PADNAMELIST;
# define PadlistARRAY(pl) ((PAD **)AvARRAY(pl))
# define PadlistNAMES(pl) (*PadlistARRAY(pl))
typedef SV PADNAME;
# define PadnamePV(pn) (SvPOKp(pn) ? SvPVX(pn) : NULL)
# define PadnameLEN(pn) SvCUR(pn)
# define PadnameOUTER(pn) (SvFAKE(pn) && !SvPAD_STATE(pn))
# define PadnamelistARRAY(pnl) AvARRAY(pnl)
# define PadnamelistMAX(pnl) AvFILLp(pnl)
# define PadARRAY(p) AvARRAY(p)
# define PadMAX(pad) AvFILLp(pad)
#endif
#ifndef av_top_index
# define av_top_index(av) AvFILL(av)
#endif
#ifndef block_end
# define block_end(a,b) Perl_block_end(aTHX_ a,b)
#endif
#ifndef block_start
# define block_start(a) Perl_block_start(aTHX_ a)
#endif
#ifndef cv_clone
# define cv_clone(a) Perl_cv_clone(aTHX_ a)
#endif
#ifndef intro_my
# define intro_my() Perl_intro_my(aTHX)
#endif
#ifndef pad_alloc
# define pad_alloc(a,b) Perl_pad_alloc(aTHX_ a,b)
#endif
#ifndef CX_CUR
# define CX_CUR() (&cxstack[cxstack_ix])
#endif
#if HAVE_PERL_VERSION(5, 24, 0)
# define OLDSAVEIX(cx) (cx->blk_oldsaveix)
#else
# define OLDSAVEIX(cx) (PL_scopestack[cx->blk_oldscopesp-1])
#endif
#ifndef OpSIBLING
# define OpSIBLING(op) ((op)->op_sibling)
#endif
#ifndef OpMORESIB_set
# define OpMORESIB_set(op,sib) ((op)->op_sibling = (sib))
#endif
#ifndef OpLASTSIB_set
/* older perls don't need to store this at all */
# define OpLASTSIB_set(op,parent)
#endif
#ifndef op_convert_list
# define op_convert_list(type, flags, o) S_op_convert_list(aTHX_ type, flags, o)
static OP *S_op_convert_list(pTHX_ I32 type, I32 flags, OP *o)
{
/* A minimal recreation just for our purposes */
assert(
/* A hardcoded list of the optypes we know this will work for */
type == OP_ENTERSUB ||
type == OP_JOIN ||
type == OP_PUSH ||
0);
o->op_type = type;
o->op_flags |= flags;
o->op_ppaddr = PL_ppaddr[type];
o = PL_check[type](aTHX_ o);
/* op_std_init() */
if(PL_opargs[type] & OA_RETSCALAR)
o = op_contextualize(o, G_SCALAR);
if(PL_opargs[type] & OA_TARGET && !o->op_targ)
o->op_targ = pad_alloc(type, SVs_PADTMP);
return o;
}
#endif
#ifndef newMETHOP_named
# define newMETHOP_named(type, flags, name) newSVOP(type, flags, name)
#endif
#ifndef PARENT_PAD_INDEX_set
# if HAVE_PERL_VERSION(5, 22, 0)
# define PARENT_PAD_INDEX_set(pn,val) (PARENT_PAD_INDEX(pn) = val)
# else
/* stolen from perl-5.20.0's pad.c */
# define PARENT_PAD_INDEX_set(sv,val) \
STMT_START { ((XPVNV*)SvANY(sv))->xnv_u.xpad_cop_seq.xlow = (val); } STMT_END
# endif
#endif
/* On Perl 5.14 this had a different name */
#ifndef pad_add_name_pvn
#define pad_add_name_pvn(name, len, flags, typestash, ourstash) MY_pad_add_name(aTHX_ name, len, flags, typestash, ourstash)
PADOFFSET MY_pad_add_name(pTHX_ const char *name, STRLEN len, U32 flags, HV *typestash, HV *ourstash)
{
/* perl 5.14's Perl_pad_add_name requires a NUL-terminated name */
SV *namesv = sv_2mortal(newSVpvn(name, len));
return Perl_pad_add_name(aTHX_ SvPV_nolen(namesv), SvCUR(namesv), flags, typestash, ourstash);
}
#endif
#if !HAVE_PERL_VERSION(5, 26, 0)
# define isIDFIRST_utf8_safe(s, e) (PERL_UNUSED_ARG(e), isIDFIRST_utf8(s))
# define isIDCONT_utf8_safe(s, e) (PERL_UNUSED_ARG(e), isIDCONT_utf8(s))
#endif

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# You may distribute under the terms of either the GNU General Public License
# or the Artistic License (the same terms as Perl itself)
#
# (C) Paul Evans, 2016-2022 -- leonerd@leonerd.org.uk
package Syntax::Keyword::Try 0.27;
use v5.14;
use warnings;
use Carp;
require XSLoader;
XSLoader::load( __PACKAGE__, our $VERSION );
=head1 NAME
C<Syntax::Keyword::Try> - a C<try/catch/finally> syntax for perl
=head1 SYNOPSIS
use Syntax::Keyword::Try;
sub foo {
try {
attempt_a_thing();
return "success";
}
catch ($e) {
warn "It failed - $e";
return "failure";
}
}
=head1 DESCRIPTION
This module provides a syntax plugin that implements exception-handling
semantics in a form familiar to users of other languages, being built on a
block labeled with the C<try> keyword, followed by at least one of a C<catch>
or C<finally> block.
As well as providing a handy syntax for this useful behaviour, this module
also serves to contain a number of code examples for how to implement parser
plugins and manipulate optrees to provide new syntax and behaviours for perl
code.
Syntax similar to this module has now been added to core perl, starting at
version 5.34.0. If you are writing new code, it is suggested that you instead
use the L<Feature::Compat::Try> module instead, as that will enable the core
feature on those supported perl versions, falling back to
C<Syntax::Keyword::Try> on older perls.
=head1 Experimental Features
Some of the features of this module are currently marked as experimental. They
will provoke warnings in the C<experimental> category, unless silenced.
You can silence this with C<no warnings 'experimental'> but then that will
silence every experimental warning, which may hide others unintentionally. For
a more fine-grained approach you can instead use the import line for this
module to only silence this module's warnings selectively:
use Syntax::Keyword::Try qw( try :experimental(typed) );
use Syntax::Keyword::Try qw( try :experimental ); # all of the above
Don't forget to import the main C<try> symbol itself, to activate the syntax.
=cut
=head1 KEYWORDS
=head2 try
try {
STATEMENTS...
}
...
A C<try> statement provides the main body of code that will be invoked, and
must be followed by either a C<catch> statement, a C<finally> statement, or
both.
Execution of the C<try> statement itself begins from the block given to the
statement and continues until either it throws an exception, or completes
successfully by reaching the end of the block. What will happen next depends
on the presence of a C<catch> or C<finally> statement immediately following
it.
The body of a C<try {}> block may contain a C<return> expression. If executed,
such an expression will cause the entire containing function to return with
the value provided. This is different from a plain C<eval {}> block, in which
circumstance only the C<eval> itself would return, not the entire function.
The body of a C<try {}> block may contain loop control expressions (C<redo>,
C<next>, C<last>) which will have their usual effect on any loops that the
C<try {}> block is contained by.
The parsing rules for the set of statements (the C<try> block and its
associated C<catch> and C<finally>) are such that they are parsed as a self-
contained statement. Because of this, there is no need to end with a
terminating semicolon.
Even though it parses as a statement and not an expression, a C<try> block can
still yield a value if it appears as the final statement in its containing
C<sub> or C<do> block. For example:
my $result = do {
try { attempt_func() }
catch ($e) { "Fallback Value" }
};
Note (especially to users of L<Try::Tiny> and similar) that the C<try {}>
block itself does not necessarily stop exceptions thrown inside it from
propagating outside. It is the presence of a later C<catch {}> block which
causes this to happen. A C<try> with only a C<finally> and no C<catch> will
still propagate exceptions up to callers as normal.
=head2 catch
...
catch ($var) {
STATEMENTS...
}
or
...
catch {
STATEMENTS...
}
A C<catch> statement provides a block of code to the preceding C<try>
statement that will be invoked in the case that the main block of code throws
an exception. Optionally a new lexical variable can be provided to store the
exception in. If not provided, the C<catch> block can inspect the raised
exception by looking in C<$@> instead.
Presence of this C<catch> statement causes any exception thrown by the
preceding C<try> block to be non-fatal to the surrounding code. If the
C<catch> block wishes to optionally handle some exceptions but not others, it
can re-raise it (or another exception) by calling C<die> in the usual manner.
As with C<try>, the body of a C<catch {}> block may also contain a C<return>
expression, which as before, has its usual meaning, causing the entire
containing function to return with the given value. The body may also contain
loop control expressions (C<redo>, C<next> or C<last>) which also have their
usual effect.
If a C<catch> statement is not given, then any exceptions raised by the C<try>
block are raised to the caller in the usual way.
=head2 catch (Typed)
...
catch ($var isa Class) { ... }
...
catch ($var =~ m/^Regexp match/) { ... }
I<Experimental; since version 0.15.>
Optionally, multiple catch statements can be provided, where each block is
given a guarding condition, to control whether or not it will catch particular
exception values. Use of this syntax will provoke an C<experimental> category
warning on supporting perl versions, unless silenced by importing the
C<:experimental(typed)> tag (see above).
Two kinds of condition are supported:
=over 4
=item *
catch ($var isa Class)
The block is invoked only if the caught exception is a blessed object, and
derives from the given package name.
On Perl version 5.32 onwards, this condition test is implemented using the
same op type that the core C<$var isa Class> syntax is provided by and works
in exactly the same way.
On older perl versions it is emulated by a compatibility function. Currently
this function does not respect a C<< ->isa >> method overload on the exception
instance. Usually this should not be a problem, as exception class types
rarely provide such a method.
=item *
catch ($var =~ m/regexp/)
The block is invoked only if the caught exception is a string that matches
the given regexp.
=back
When an exception is caught, each condition is tested in the order they are
written in, until a matching case is found. If such a case is found the
corresponding block is invoked, and no further condition is tested. If no
contional block matched and there is a default (unconditional) block at the
end then that is invoked instead. If no such block exists, then the exception
is propagated up to the calling scope.
=head2 finally
...
finally {
STATEMENTS...
}
A C<finally> statement provides a block of code to the preceding C<try>
statement (or C<try/catch> pair) which is executed afterwards, both in the
case of a normal execution or a thrown exception. This code block may be used
to provide whatever clean-up operations might be required by preceding code.
Because it is executed during a stack cleanup operation, a C<finally {}> block
may not cause the containing function to return, or to alter the return value
of it. It also cannot see the containing function's C<@_> arguments array
(though as it is block scoped within the function, it will continue to share
any normal lexical variables declared up until that point). It is protected
from disturbing the value of C<$@>. If the C<finally {}> block code throws an
exception, this will be printed as a warning and discarded, leaving C<$@>
containing the original exception, if one existed.
=head1 OTHER MODULES
There are already quite a number of modules on CPAN that provide a
C<try/catch>-like syntax for Perl.
=over 2
=item *
L<Try>
=item *
L<TryCatch>
=item *
L<Try::Tiny>
=item *
L<Syntax::Feature::Try>
=back
In addition, core perl itself gained a C<try/catch> syntax based on this
module at version 5.34.0. It is available as C<use feature 'try'>.
They are compared here, by feature:
=head2 True syntax plugin
Like L<Try> and L<Syntax::Feature::Try>, this module is implemented as a true
syntax plugin, allowing it to provide new parsing rules not available to
simple functions. Most notably here it means that the resulting combination
does not need to end in a semicolon.
The core C<feature 'try'> is also implemented as true native syntax in the
perl parser.
In comparison, L<Try::Tiny> is plain perl and provides its functionality using
regular perl functions; as such its syntax requires the trailing semicolon.
L<TryCatch> is a hybrid that uses L<Devel::Declare> to parse the syntax tree.
=head2 C<@_> in a try or catch block
Because the C<try> and C<catch> block code is contained in a true block rather
than an entire anonymous subroutine, invoking it does not interfere with the
C<@_> arguments array. Code inside these blocks can interact with the
containing function's array as before.
This feature is unique among these modules; none of the others listed have
this ability.
The core C<feature 'try'> also behaves in this manner.
=head2 C<return> in a try or catch block
Like L<TryCatch> and L<Syntax::Feature::Try>, the C<return> statement has its
usual effect within a subroutine containing syntax provided by this module.
Namely, it causes the containing C<sub> itself to return.
It also behaves this way using the core C<feature 'try'>.
In comparison, using L<Try> or L<Try::Tiny> mean that a C<return> statement
will only exit from the C<try> block.
=head2 C<next>/C<last>/C<redo> in a try or catch block
The loop control keywords of C<next>, C<last> and C<redo> have their usual
effect on dynamically contained loops.
These also work fine when using the core C<feature 'try'>.
L<Syntax::Feature::Try> documents that these do not work there. The other
modules make no statement either way.
=head2 Value Semantics
Like L<Try> and L<Syntax::Feature::Try>, the syntax provided by this module
only works as a syntax-level statement and not an expression. You cannot
assign from the result of a C<try> block. A common workaround is to wrap
the C<try/catch> statement inside a C<do> block, where its final expression
can be captured and used as a value.
The same C<do> block wrapping also works for the core C<feature 'try'>.
In comparison, the behaviour implemented by L<Try::Tiny> can be used as a
valued expression, such as assigned to a variable or returned to the caller of
its containing function.
=head2 C<try> without C<catch>
Like L<Syntax::Feature::Try>, the syntax provided by this module allows a
C<try> block to be followed by only a C<finally> block, with no C<catch>. In
this case, exceptions thrown by code contained by the C<try> are not
suppressed, instead they propagate as normal to callers. This matches the
behaviour familiar to Java or C++ programmers.
In comparison, the code provided by L<Try> and L<Try::Tiny> always suppress
exception propagation even without an actual C<catch> block.
The L<TryCatch> module does not allow a C<try> block not followed by C<catch>.
The core C<feature 'try'> does not implement C<finally> at all, and also
requires that every C<try> block be followed by a C<catch>.
=head2 Typed C<catch>
L<Try> and L<Try::Tiny> make no attempt to perform any kind of typed dispatch
to distinguish kinds of exception caught by C<catch> blocks.
Likewise the core C<feature 'try'> currently does not provide this ability,
though it remains an area of ongoing design work.
L<TryCatch> and L<Syntax::Feature::Try> both attempt to provide a kind of
typed dispatch where different classes of exception are caught by different
blocks of code, or propagated up entirely to callers.
This module provides such an ability, via the currently-experimental
C<catch (VAR cond...)> syntax.
The design thoughts continue on the RT ticket
L<https://rt.cpan.org/Ticket/Display.html?id=123918>.
=cut
sub import
{
my $class = shift;
my $caller = caller;
$class->import_into( $caller, @_ );
}
my @EXPERIMENTAL = qw( typed );
sub import_into
{
my $class = shift;
my ( $caller, @syms ) = @_;
@syms or @syms = qw( try );
my %syms = map { $_ => 1 } @syms;
$^H{"Syntax::Keyword::Try/try"}++ if delete $syms{try};
# Largely for Feature::Compat::Try's benefit
$^H{"Syntax::Keyword::Try/no_finally"}++ if delete $syms{"-no_finally"};
$^H{"Syntax::Keyword::Try/require_catch"}++ if delete $syms{"-require_catch"};
$^H{"Syntax::Keyword::Try/require_var"}++ if delete $syms{"-require_var"};
# stablised experiments
delete $syms{":experimental($_)"} for qw( var );
foreach ( @EXPERIMENTAL ) {
$^H{"Syntax::Keyword::Try/experimental($_)"}++ if delete $syms{":experimental($_)"};
}
if( delete $syms{":experimental"} ) {
$^H{"Syntax::Keyword::Try/experimental($_)"}++ for @EXPERIMENTAL;
}
# Ignore requests for these, as they come automatically with `try`
delete @syms{qw( catch finally )};
if( $syms{try_value} or $syms{":experimental(try_value)"} ) {
croak "The 'try_value' experimental feature is now removed\n" .
"Instead, you should use do { try ... } to yield a value from a try/catch statement";
}
croak "Unrecognised import symbols @{[ keys %syms ]}" if keys %syms;
}
=head1 WITH OTHER MODULES
=head2 Future::AsyncAwait
As of C<Future::AsyncAwait> version 0.10 and L<Syntax::Keyword::Try> version
0.07, cross-module integration tests assert that basic C<try/catch> blocks
inside an C<async sub> work correctly, including those that attempt to
C<return> from inside C<try>.
use Future::AsyncAwait;
use Syntax::Keyword::Try;
async sub attempt
{
try {
await func();
return "success";
}
catch {
return "failed";
}
}
=head1 ISSUES
=head2 Thread-safety at load time cannot be assured before perl 5.16
On F<perl> versions 5.16 and above this module is thread-safe.
On F<perl> version 5.14 this module is thread-safe provided that it is
C<use>d before any additional threads are created.
However, when using 5.14 there is a race condition if this module is loaded
late in the program startup, after additional threads have been created. This
leads to the potential for it to be started up multiple times concurrently,
which creates data races when modifying internal structures and likely leads
to a segmentation fault, either during load or soon after when more code is
compiled.
As a workaround, for any such program that creates multiple threads, loads
additional code (such as dynamically-discovered plugins), and has to run on
5.14, it should make sure to
use Syntax::Keyword::Try;
early on in startup, before it spins out any additional threads.
(See also L<https://rt.cpan.org/Public/Bug/Display.html?id=123547>)
=head2 $@ is not local'ised by C<try do> before perl 5.24
On F<perl> versions 5.24 and above, or when using only control-flow statement
syntax, C<$@> is always correctly C<local>ised.
However, when using the experimental value-yielding expression version
C<try do {...}> on perl versions 5.22 or older, the C<local>isation of C<$@>
does not correctly apply around the expression. After such an expression, the
value of C<$@> will leak out if a failure happened and the C<catch> block was
invoked, overwriting any previous value that was visible there.
(See also L<https://rt.cpan.org/Public/Bug/Display.html?id=124366>)
=head1 ACKNOWLEDGEMENTS
With thanks to C<Zefram>, C<ilmari> and others from C<irc.perl.org/#p5p> for
assisting with trickier bits of XS logic.
=head1 AUTHOR
Paul Evans <leonerd@leonerd.org.uk>
=cut
0x55AA;

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/* You may distribute under the terms of either the GNU General Public License
* or the Artistic License (the same terms as Perl itself)
*
* (C) Paul Evans, 2016-2021 -- leonerd@leonerd.org.uk
*/
#include "EXTERN.h"
#include "perl.h"
#include "XSUB.h"
#include "XSParseKeyword.h"
#include "perl-backcompat.c.inc"
#if HAVE_PERL_VERSION(5,32,0)
# define HAVE_OP_ISA
#endif
#if HAVE_PERL_VERSION(5,26,0)
# define HAVE_OP_SIBPARENT
#endif
#if HAVE_PERL_VERSION(5,19,4)
typedef SSize_t array_ix_t;
#else /* <5.19.4 */
typedef I32 array_ix_t;
#endif /* <5.19.4 */
#include "perl-additions.c.inc"
#include "optree-additions.c.inc"
#include "op_sibling_splice.c.inc"
#include "newOP_CUSTOM.c.inc"
static OP *pp_entertrycatch(pTHX);
static OP *pp_catch(pTHX);
/*
* A modified version of pp_return for returning from inside a try block.
* To do this, we unwind the context stack to just past the CXt_EVAL and then
* chain to the regular OP_RETURN func
*/
static OP *pp_returnintry(pTHX)
{
I32 cxix;
for (cxix = cxstack_ix; cxix; cxix--) {
if(CxTYPE(&cxstack[cxix]) == CXt_SUB)
break;
if(CxTYPE(&cxstack[cxix]) == CXt_EVAL && CxTRYBLOCK(&cxstack[cxix])) {
/* If this CXt_EVAL frame came from our own ENTERTRYCATCH, then the
* retop should point at an OP_CUSTOM and its first grand-child will be
* our custom modified ENTERTRY. We can skip over it and continue in
* this case.
*/
OP *retop = cxstack[cxix].blk_eval.retop;
OP *leave, *enter;
if(retop->op_type == OP_CUSTOM && retop->op_ppaddr == &pp_catch &&
(leave = cLOGOPx(retop)->op_first) && leave->op_type == OP_LEAVETRY &&
(enter = cLOGOPx(leave)->op_first) && enter->op_type == OP_ENTERTRY &&
enter->op_ppaddr == &pp_entertrycatch) {
continue;
}
/* We have to stop at any other kind of CXt_EVAL */
break;
}
}
if(!cxix)
croak("Unable to find an CXt_SUB to pop back to");
I32 gimme = cxstack[cxix].blk_gimme;
SV *retval;
/* chunks of this code inspired by
* ZEFRAM/Scope-Escape-0.005/lib/Scope/Escape.xs
*/
switch(gimme) {
case G_VOID:
(void)POPMARK;
break;
case G_SCALAR: {
dSP;
dMARK;
retval = (MARK == SP) ? &PL_sv_undef : TOPs;
SvREFCNT_inc(retval);
sv_2mortal(retval);
break;
}
case G_LIST: {
dSP;
dMARK;
SV **retvals = MARK+1;
array_ix_t retcount = SP-MARK;
array_ix_t i;
AV *retav = newAV();
retval = (SV *)retav;
sv_2mortal(retval);
av_fill(retav, retcount-1);
Copy(retvals, AvARRAY(retav), retcount, SV *);
for(i = 0; i < retcount; i++)
SvREFCNT_inc(retvals[i]);
break;
}
}
dounwind(cxix);
/* Now put the value back */
switch(gimme) {
case G_VOID: {
dSP;
PUSHMARK(SP);
break;
}
case G_SCALAR: {
dSP;
PUSHMARK(SP);
XPUSHs(retval);
PUTBACK;
break;
}
case G_LIST: {
dSP;
PUSHMARK(SP);
AV *retav = (AV *)retval;
array_ix_t retcount = av_len(retav) + 1; /* because av_len means top index */
EXTEND(SP, retcount);
Copy(AvARRAY(retav), SP+1, retcount, SV *);
SP += retcount;
PUTBACK;
break;
}
}
return PL_ppaddr[OP_RETURN](aTHX);
}
/*
* A custom SVOP that takes a CV and arranges for it to be invoked on scope
* leave
*/
static XOP xop_pushfinally;
static void invoke_finally(pTHX_ void *arg)
{
CV *finally = arg;
dSP;
PUSHMARK(SP);
call_sv((SV *)finally, G_DISCARD|G_EVAL|G_KEEPERR);
SvREFCNT_dec(finally);
}
static OP *pp_pushfinally(pTHX)
{
CV *finally = (CV *)cSVOP->op_sv;
/* finally is a closure protosub; we have to clone it into a real sub.
* If we do this now then captured lexicals still work even around
* Future::AsyncAwait (see RT122796)
* */
SAVEDESTRUCTOR_X(&invoke_finally, (SV *)cv_clone(finally));
return PL_op->op_next;
}
#define newLOCALISEOP(gv) MY_newLOCALISEOP(aTHX_ gv)
static OP *MY_newLOCALISEOP(pTHX_ GV *gv)
{
OP *op = newGVOP(OP_GVSV, 0, gv);
op->op_private |= OPpLVAL_INTRO;
return op;
}
#define newSTATEOP_nowarnings() MY_newSTATEOP_nowarnings(aTHX)
static OP *MY_newSTATEOP_nowarnings(pTHX)
{
OP *op = newSTATEOP(0, NULL, NULL);
STRLEN *warnings = ((COP *)op)->cop_warnings;
char *warning_bits;
if(warnings == pWARN_NONE)
return op;
if(warnings == pWARN_STD)
/* TODO: understand what STD vs ALL means */
warning_bits = WARN_ALLstring;
else if(warnings == pWARN_ALL)
warning_bits = WARN_ALLstring;
else
warning_bits = (char *)(warnings + 1);
warnings = Perl_new_warnings_bitfield(aTHX_ warnings, warning_bits, WARNsize);
((COP *)op)->cop_warnings = warnings;
warning_bits = (char *)(warnings + 1);
warning_bits[(2*WARN_EXITING) / 8] &= ~(1 << (2*WARN_EXITING % 8));
return op;
}
static void rethread_op(OP *op, OP *old, OP *new)
{
if(op->op_next == old)
op->op_next = new;
switch(OP_CLASS(op)) {
case OA_LOGOP:
if(cLOGOPx(op)->op_other == old)
cLOGOPx(op)->op_other = new;
break;
case OA_LISTOP:
if(cLISTOPx(op)->op_last == old)
cLISTOPx(op)->op_last = new;
break;
}
if(op->op_flags & OPf_KIDS) {
OP *kid;
for(kid = cUNOPx(op)->op_first; kid; kid = OpSIBLING(kid))
rethread_op(kid, old, new);
}
}
#define walk_optree_try_in_eval(op_ptr, root) MY_walk_optree_try_in_eval(aTHX_ op_ptr, root)
static void MY_walk_optree_try_in_eval(pTHX_ OP **op_ptr, OP *root);
static void MY_walk_optree_try_in_eval(pTHX_ OP **op_ptr, OP *root)
{
OP *op = *op_ptr;
switch(op->op_type) {
/* Fix 'return' to unwind the CXt_EVAL block that implements try{} first */
case OP_RETURN:
op->op_ppaddr = &pp_returnintry;
break;
/* wrap no warnings 'exiting' around loop controls */
case OP_NEXT:
case OP_LAST:
case OP_REDO:
{
#ifdef HAVE_OP_SIBPARENT
OP *parent = OpHAS_SIBLING(op) ? NULL : op->op_sibparent;
#endif
OP *stateop = newSTATEOP_nowarnings();
OP *scope = newLISTOP(OP_SCOPE, 0,
stateop, op);
#ifdef HAVE_OP_SIBPARENT
if(parent)
OpLASTSIB_set(scope, parent);
else
OpLASTSIB_set(scope, NULL);
#else
op->op_sibling = NULL;
#endif
/* Rethread */
scope->op_next = stateop;
stateop->op_next = op;
*op_ptr = scope;
}
break;
/* Don't enter inside nested eval{} blocks */
case OP_LEAVETRY:
return;
}
if(op->op_flags & OPf_KIDS) {
OP *kid, *next, *prev = NULL;
for(kid = cUNOPx(op)->op_first; kid; kid = next) {
OP *newkid = kid;
next = OpSIBLING(kid);
walk_optree_try_in_eval(&newkid, root);
if(newkid != kid) {
rethread_op(root, kid, newkid);
if(prev) {
OpMORESIB_set(prev, newkid);
}
else
cUNOPx(op)->op_first = newkid;
if(next)
OpMORESIB_set(newkid, next);
}
prev = kid;
}
}
}
static OP *pp_entertrycatch(pTHX)
{
/* Localise the errgv */
save_scalar(PL_errgv);
return PL_ppaddr[OP_ENTERTRY](aTHX);
}
static XOP xop_catch;
static OP *pp_catch(pTHX)
{
/* If an error didn't happen, then ERRSV will be both not true and not a
* reference. If it's a reference, then an error definitely happened
*/
if(SvROK(ERRSV) || SvTRUE(ERRSV))
return cLOGOP->op_other;
else
return cLOGOP->op_next;
}
#define newENTERTRYCATCHOP(flags, try, catch) MY_newENTERTRYCATCHOP(aTHX_ flags, try, catch)
static OP *MY_newENTERTRYCATCHOP(pTHX_ U32 flags, OP *try, OP *catch)
{
OP *enter, *entertry, *ret;
/* Walk the block for OP_RETURN ops, so we can apply a hack to them to
* make
* try { return }
* return from the containing sub, not just the eval block
*/
walk_optree_try_in_eval(&try, try);
enter = newUNOP(OP_ENTERTRY, 0, try);
/* despite calling newUNOP(OP_ENTERTRY,...) the returned root node is the
* OP_LEAVETRY, whose first child is the ENTERTRY we wanted
*/
entertry = ((UNOP *)enter)->op_first;
entertry->op_ppaddr = &pp_entertrycatch;
/* If we call newLOGOP_CUSTOM it will op_contextualize the enter block into
* G_SCALAR. This is not what we want
*/
{
LOGOP *logop;
OP *first = enter, *other = newLISTOP(OP_SCOPE, 0, catch, NULL);
NewOp(1101, logop, 1, LOGOP);
logop->op_type = OP_CUSTOM;
logop->op_ppaddr = &pp_catch;
logop->op_first = first;
logop->op_flags = OPf_KIDS;
logop->op_other = LINKLIST(other);
logop->op_next = LINKLIST(first);
enter->op_next = (OP *)logop;
#if HAVE_PERL_VERSION(5, 22, 0)
op_sibling_splice((OP *)logop, first, 0, other);
#else
first->op_sibling = other;
#endif
ret = newUNOP(OP_NULL, 0, (OP *)logop);
other->op_next = ret;
}
return ret;
}
#ifndef HAVE_OP_ISA
static XOP xop_isa;
/* Totally stolen from perl 5.32.0's pp.c */
#define sv_isa_sv(sv, namesv) S_sv_isa_sv(aTHX_ sv, namesv)
static bool S_sv_isa_sv(pTHX_ SV *sv, SV *namesv)
{
if(!SvROK(sv) || !SvOBJECT(SvRV(sv)))
return FALSE;
/* TODO: ->isa invocation */
#if HAVE_PERL_VERSION(5,16,0)
return sv_derived_from_sv(sv, namesv, 0);
#else
return sv_derived_from(sv, SvPV_nolen(namesv));
#endif
}
static OP *pp_isa(pTHX)
{
dSP;
SV *left, *right;
right = POPs;
left = TOPs;
SETs(boolSV(sv_isa_sv(left, right)));
RETURN;
}
#endif
static int build_try(pTHX_ OP **out, XSParseKeywordPiece *args[], size_t nargs, void *hookdata)
{
U32 argi = 0;
OP *try = args[argi++]->op;
OP *ret = NULL;
HV *hints = GvHV(PL_hintgv);
bool require_catch = hints && hv_fetchs(hints, "Syntax::Keyword::Try/require_catch", 0);
bool require_var = hints && hv_fetchs(hints, "Syntax::Keyword::Try/require_var", 0);
U32 ncatches = args[argi++]->i;
AV *condcatch = NULL;
OP *catch = NULL;
while(ncatches--) {
bool has_catchvar = args[argi++]->i;
PADOFFSET catchvar = has_catchvar ? args[argi++]->padix : 0;
int catchtype = has_catchvar ? args[argi++]->i : -1;
bool warned = FALSE;
OP *condop = NULL;
switch(catchtype) {
case -1: /* no type */
break;
case 0: /* isa */
{
OP *type = args[argi++]->op;
#ifdef HAVE_OP_ISA
condop = newBINOP(OP_ISA, 0,
newPADxVOP(OP_PADSV, catchvar, 0, 0), type);
#else
/* Allow a bareword on RHS of `isa` */
if(type->op_type == OP_CONST)
type->op_private &= ~(OPpCONST_BARE|OPpCONST_STRICT);
condop = newBINOP_CUSTOM(&pp_isa, 0,
newPADxVOP(OP_PADSV, catchvar, 0, 0), type);
#endif
break;
}
case 1: /* =~ */
{
OP *regexp = args[argi++]->op;
if(regexp->op_type != OP_MATCH || cPMOPx(regexp)->op_first)
croak("Expected a regexp match");
#if HAVE_PERL_VERSION(5,22,0)
/* Perl 5.22+ uses op_targ on OP_MATCH directly */
regexp->op_targ = catchvar;
#else
/* Older perls need a stacked OP_PADSV op */
cPMOPx(regexp)->op_first = newPADxVOP(OP_PADSV, catchvar, 0, 0);
regexp->op_flags |= OPf_KIDS|OPf_STACKED;
#endif
condop = regexp;
break;
}
default:
croak("TODO\n");
}
#ifdef WARN_EXPERIMENTAL
if(condop && !warned &&
(!hints || !hv_fetchs(hints, "Syntax::Keyword::Try/experimental(typed)", 0))) {
warned = true;
Perl_ck_warner(aTHX_ packWARN(WARN_EXPERIMENTAL),
"typed catch syntax is experimental and may be changed or removed without notice");
}
#endif
OP *body = args[argi++]->op;
if(require_var && !has_catchvar)
croak("Expected (VAR) for catch");
if(catch)
croak("Already have a default catch {} block");
OP *assignop = NULL;
if(catchvar) {
/* my $var = $@ */
assignop = newBINOP(OP_SASSIGN, 0,
newGVOP(OP_GVSV, 0, PL_errgv), newPADxVOP(OP_PADSV, catchvar, OPf_MOD, OPpLVAL_INTRO));
}
if(condop) {
if(!condcatch)
condcatch = newAV();
av_push(condcatch, (SV *)op_append_elem(OP_LINESEQ, assignop, condop));
av_push(condcatch, (SV *)body);
/* catch remains NULL for now */
}
else if(assignop) {
catch = op_prepend_elem(OP_LINESEQ,
assignop, body);
}
else
catch = body;
}
if(condcatch) {
I32 i;
if(!catch)
/* A default fallthrough */
/* die $@ */
catch = newLISTOP(OP_DIE, 0,
newOP(OP_PUSHMARK, 0), newGVOP(OP_GVSV, 0, PL_errgv));
for(i = AvFILL(condcatch)-1; i >= 0; i -= 2) {
OP *body = (OP *)av_pop(condcatch),
*condop = (OP *)av_pop(condcatch);
catch = newCONDOP(0, condop, op_scope(body), catch);
}
SvREFCNT_dec(condcatch);
}
if(require_catch && !catch)
croak("Expected a catch {} block");
bool no_finally = hints && hv_fetchs(hints, "Syntax::Keyword::Try/no_finally", 0);
U32 has_finally = args[argi++]->i;
CV *finally = has_finally ? args[argi++]->cv : NULL;
if(no_finally && finally)
croak("finally {} is not permitted here");
if(!catch && !finally) {
op_free(try);
croak(no_finally
? "Expected try {} to be followed by catch {}"
: "Expected try {} to be followed by either catch {} or finally {}");
}
ret = try;
if(catch) {
ret = newENTERTRYCATCHOP(0, try, catch);
}
/* If there's a finally, make
* $RET = OP_PUSHFINALLY($FINALLY); $RET
*/
if(finally) {
ret = op_prepend_elem(OP_LINESEQ,
newSVOP_CUSTOM(&pp_pushfinally, 0, (SV *)finally),
ret);
}
ret = op_append_list(OP_LEAVE,
newOP(OP_ENTER, 0),
ret);
*out = ret;
return KEYWORD_PLUGIN_STMT;
}
static struct XSParseKeywordHooks hooks_try = {
.permit_hintkey = "Syntax::Keyword::Try/try",
.pieces = (const struct XSParseKeywordPieceType []){
XPK_BLOCK,
XPK_REPEATED(
XPK_LITERAL("catch"),
XPK_PREFIXED_BLOCK(
/* optionally ($var), ($var isa Type) or ($var =~ m/.../) */
XPK_PARENSCOPE_OPT(
XPK_LEXVAR_MY(XPK_LEXVAR_SCALAR),
XPK_CHOICE(
XPK_SEQUENCE(XPK_LITERAL("isa"), XPK_TERMEXPR),
XPK_SEQUENCE(XPK_LITERAL("=~"), XPK_TERMEXPR)
)
)
)
),
XPK_OPTIONAL(
XPK_LITERAL("finally"), XPK_ANONSUB
),
{0},
},
.build = &build_try,
};
MODULE = Syntax::Keyword::Try PACKAGE = Syntax::Keyword::Try
BOOT:
XopENTRY_set(&xop_catch, xop_name, "catch");
XopENTRY_set(&xop_catch, xop_desc,
"optionally invoke the catch block if required");
XopENTRY_set(&xop_catch, xop_class, OA_LOGOP);
Perl_custom_op_register(aTHX_ &pp_catch, &xop_catch);
XopENTRY_set(&xop_pushfinally, xop_name, "pushfinally");
XopENTRY_set(&xop_pushfinally, xop_desc,
"arrange for a CV to be invoked at scope exit");
XopENTRY_set(&xop_pushfinally, xop_class, OA_SVOP);
Perl_custom_op_register(aTHX_ &pp_pushfinally, &xop_pushfinally);
#ifndef HAVE_OP_ISA
XopENTRY_set(&xop_isa, xop_name, "isa");
XopENTRY_set(&xop_isa, xop_desc,
"check if a value is an object of the given class");
XopENTRY_set(&xop_isa, xop_class, OA_BINOP);
Perl_custom_op_register(aTHX_ &pp_isa, &xop_isa);
#endif
boot_xs_parse_keyword(0.06);
register_xs_parse_keyword("try", &hooks_try, NULL);

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# You may distribute under the terms of either the GNU General Public License
# or the Artistic License (the same terms as Perl itself)
#
# (C) Paul Evans, 2021 -- leonerd@leonerd.org.uk
package Syntax::Keyword::Try::Deparse 0.27;
use v5.14;
use warnings;
use B qw( opnumber );
require B::Deparse;
use constant {
OP_CUSTOM => opnumber('custom'),
OP_ENTER => opnumber('enter'),
OP_LINESEQ => opnumber('lineseq'),
};
=head1 NAME
C<Syntax::Keyword::Try::Deparse> - L<B::Deparse> support for L<Syntax::Keyword::Try>
=head1 DESCRIPTION
Loading this module will apply some hacks onto L<B::Deparse> that attempts to
provide deparse support for code which uses the syntax provided by
L<Syntax::Keyword::Try>.
=cut
my $orig_pp_leave;
{
no warnings 'redefine';
no strict 'refs';
$orig_pp_leave = *{"B::Deparse::pp_leave"}{CODE};
*{"B::Deparse::pp_leave"} = \&pp_leave;
}
sub pp_leave
{
my $self = shift;
my ( $op ) = @_;
my $enter = $op->first;
$enter->type == OP_ENTER or
return $self->$orig_pp_leave( @_ );
my $body = $enter->sibling;
my $first = $body->first;
my $finally = "";
if( $body->type == OP_LINESEQ and $first->name eq "pushfinally" ) {
my $finally_cv = $first->sv;
$finally = "\nfinally " . $self->deparse_sub( $finally_cv ) . "\cK";
$first = $first->sibling;
$first = $first->sibling while $first and $first->name eq "lineseq";
# Jump over a scope op
if( $first->type == 0 ) {
$body = $first;
$first = $first->first;
}
}
if( $first->type == OP_CUSTOM and $first->name eq "catch" ) {
# This is a try/catch block
shift;
return $self->deparse( $body, @_ ) . $finally;
}
elsif( length $finally ) {
# Body is the remaining siblings. We'll have to do them all together
my $try = B::Deparse::scopeop( 1, $self, $body, 0 );
return "try {\n\t$try\n\b}" . $finally;
}
return $orig_pp_leave->($self, @_);
}
sub B::Deparse::pp_catch
{
my $self = shift;
my ( $op ) = @_;
my $tryop = $op->first;
my $catchop = $op->first->sibling;
my $try = $self->pp_leave($tryop, 0);
# skip the OP_SCOPE and dive into the OP_LINESEQ inside
#
# TODO: Try to detect the `catch my $e` variable, though that will be hard
# to dishtinguish from actual code that really does that
my $catch = $self->deparse($catchop->first, 0);
return "try {\n\t$try\n\b}\ncatch {\n\t$catch\n\b}\cK";
}
=head1 TODO
Correctly handle typed dispatch cases
(C<catch($var isa CLASS)>, C<catch($var =~ m/pattern/)>)
=cut
=head1 AUTHOR
Paul Evans <leonerd@leonerd.org.uk>
=cut
0x55AA;

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#!/usr/bin/perl
use v5.14;
use warnings;
use Test::More;
use_ok( "Syntax::Keyword::Try" );
done_testing;

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#!/usr/bin/perl
use v5.14;
use warnings;
use Test::More;
use Syntax::Keyword::Try;
# try success
{
my $s;
try {
$s = 1;
}
catch ($e) {
$s = 2;
}
is( $s, 1, 'sucessful try{} runs' );
}
# try catches
{
my $s;
ok( eval {
try {
die "oopsie";
}
catch ($e) { }
$s = 3;
"ok";
}, 'try { die } is not fatal' );
is( $s, 3, 'code after try{} runs' );
}
# exceptions that are false
{
my $caught;
try {
die FALSE->new;
}
catch ($e) {
$caught++;
}
ok( $caught, 'catch{} sees a false exception' );
{
package FALSE;
use overload 'bool' => sub { 0 };
sub new { bless [], shift }
}
}
# catch sees exception
{
my $caught;
try {
die "oopsie";
}
catch ($e) {
$caught = $e;
}
like( $caught, qr/^oopsie at /, 'catch{} sees $@' );
}
# catch block executes
{
my $s;
try {
die "oopsie";
}
catch ($e) {
$s = 4;
}
is( $s, 4, 'catch{} of failed try{} runs' );
}
# catch can rethrow
{
my $caught;
ok( !eval {
try { die "oopsie"; }
catch ($e) { $caught = $e; die $e }
}, 'die in catch{} is fatal' );
my $e = $@;
like( $e, qr/^oopsie at /, 'exception is thrown' );
like( $caught, qr/^oopsie at /, 'exception was seen by catch{}' );
}
# catch without VAR
{
try {
die "caught\n";
}
catch {
my $e = $@;
is( $e, "caught\n", 'exception visible in $@' );
}
}
# catch lexical does not retain
{
my $destroyed;
sub Canary::DESTROY { $destroyed++ }
try {
die bless [], "Canary";
}
catch ($e) {
# don't touch $e
}
ok( $destroyed, 'catch ($var) does not retain value' );
}
done_testing;

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t/02tryfinally.t Normal file
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#!/usr/bin/perl
use v5.14;
use warnings;
use Test::More;
use Syntax::Keyword::Try;
# try success
{
my $s;
try {
$s = 1;
}
finally {
$s = 2;
}
is( $s, 2, 'sucessful try{} runs finally{}' );
}
# try failure
{
my $s;
my $e;
ok( !eval {
try {
die "oopsie";
}
finally {
$e = $@;
$s = 3;
}
}, 'failed try{} throws' );
my $dollarat = $@;
is( $s, 3, 'failed try{} runs finally{}' );
like( $e, qr/^oopsie at /, 'finally{} sees $@' );
like( $dollarat, qr/^oopsie at /, 'try/finally leaves $@ intact' );
}
# finally runs on 'return'
{
my $final;
( sub {
try {
return;
}
finally {
$final++;
}
} )->();
ok( $final, 'finally{} runs after return' );
}
# finally runs on 'goto'
{
my $final;
try {
goto after;
}
finally {
$final++;
}
after:
ok( $final, 'finally{} runs after goto' );
}
# finally runs on 'last'
{
my $final;
LOOP: {
try {
last LOOP;
}
finally {
$final++;
}
}
ok( $final, 'finally{} runs after last' );
}
done_testing;

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#!/usr/bin/perl
use v5.14;
use warnings;
use Test::More;
use Syntax::Keyword::Try;
# try success
{
my $s;
try {
$s = 1; # overwritten
}
catch ($e) {
die "FAIL";
}
finally {
$s = 2;
}
is( $s, 2, 't/c/f runs finally' );
}
# try failure
{
my $s;
try {
die "oopsie";
}
catch ($e) {
$s = 3;
}
finally {
$s++;
}
is( $s, 4, 't/c/f runs catch{} and finally{} on failure' );
}
done_testing;

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#!/usr/bin/perl
use v5.14;
use warnings;
use Test::More;
use Syntax::Keyword::Try qw( try :experimental );
sub func
{
my ( $ret, $except ) = @_;
try {
die $except if $except;
return "ret => $ret";
}
catch ($e isa X) {
return "X => [@$e]";
}
catch ($e =~ m/^Cannot /) {
chomp $e;
return "cannot => $e";
}
catch ($e) {
return "default => $e";
}
}
is( func( 123 ), "ret => 123", 'typed catch succeeds' );
is( func( 0, "failure\n" ), "default => failure\n",
'typed catch default case' );
is( func( 0, bless [45], "X" ), "X => [45]",
'typed catch isa case' );
is( func( 0, "Cannot do X\n" ), "cannot => Cannot do X",
'typed catch regexp case' );
sub fallthrough
{
my ( $except ) = @_;
try {
die $except;
}
catch ($e isa X) {
return "X => [@$e]";
}
# no default
}
is( fallthrough( bless ["OK"], "X" ), "X => [OK]",
'typed catch not fallthrough' );
is( eval { fallthrough( "Oopsie\n" ); 1 } ? undef : $@, "Oopsie\n",
'typed catch fallthrough' );
done_testing;

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#!/usr/bin/perl
use v5.14;
use warnings;
use Test::More;
use Syntax::Keyword::Try;
# try gets @_
{
my @args;
( sub {
try { @args = @_ }
catch ($e) {}
} )->( 1, 2, 3 );
is_deeply( \@args, [ 1, 2, 3 ], 'try{} sees surrounding @_' );
}
# catch sees @_
{
my @args;
( sub {
try { die "oopsie" }
catch ($e) { @args = @_ }
} )->( 4, 5, 6 );
is_deeply( \@args, [ 4, 5, 6 ], 'catch{} sees @_' );
}
done_testing;

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#!/usr/bin/perl
use v5.14;
use warnings;
use Test::More;
use Syntax::Keyword::Try;
# try can apply loop controls
{
my $count = 0;
LOOP: {
try {
$count++;
redo LOOP if $count < 2;
}
catch ($e) { }
}
is( $count, 2, 'try{redo} works' );
$count = 0;
my $after = 0;
LOOP2: {
try {
last LOOP2;
$after++; # just to put a statement after 'last'
}
catch ($e) { }
$count++;
}
is( $count, 0, 'try{last} works' );
}
# catch can apply loop controls
{
my $count = 0;
LOOP: {
try {
die "oopsie";
}
catch ($e) {
$count++;
redo LOOP if $count < 2;
}
}
is( $count, 2, 'catch{redo} works' );
$count = 0;
LOOP2: {
try {
die "oopsie";
}
catch ($e) {
last LOOP2;
}
$count++;
}
is( $count, 0, 'catch{last} works' );
}
done_testing;

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#!/usr/bin/perl
use v5.14;
use warnings;
use Test::More;
use Syntax::Keyword::Try;
# return from try
{
my $after;
( sub {
try { return }
catch ($e) {}
$after++;
} )->();
ok( !$after, 'code after try{return} in void context is not invoked' );
}
# return SCALAR from try
{
is(
scalar ( sub {
try { return "result" }
catch ($e) {}
return "nope";
} )->(),
"result",
'return SCALAR in try yields correct value'
);
}
# return LIST from try
{
is_deeply(
[ sub {
try { return qw( A B C ) } catch ($e) {}
}->() ],
[qw( A B C )],
'return LIST in try yields correct values'
);
}
# return from two nested try{}s
{
my $after;
is(
( sub {
try {
try { return "result" }
catch ($e) {}
}
catch ($e) {}
$after++;
return "nope";
} )->(),
"result",
'return in try{try{}} leaves containing function'
);
ok( !$after, 'code after try{try{return}} is not invoked' );
}
# return inside eval{} inside try{}
{
is(
( sub {
my $two;
try {
my $one = eval { return 1 };
$two = $one + 1;
}
catch ($e) {}
return $two;
} )->(),
2,
'return in eval{} inside try{} behaves as expected'
);
}
# return inside try{} inside eval{}
{
is(
( sub {
my $ret = eval {
try { return "part"; }
catch ($e) {}
};
return "($ret)";
} )->(),
"(part)",
'return in try{} inside eval{}'
);
}
# return from catch
{
is(
( sub {
try { die "oopsie" }
catch ($e) { return "result" }
return "nope";
} )->(),
"result",
'return in catch leaves containing function'
);
}
done_testing;

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#!/usr/bin/perl
use v5.14;
use warnings;
use Test::More;
use Syntax::Keyword::Try;
# finally does not disturb $@
{
my $warnings = "";
local $SIG{__WARN__} = sub { $warnings .= $_[0]; };
ok( !eval {
try {
die "oopsie";
}
finally {
die "double oops";
}
1;
}, 'die in both try{} and finally{} is still fatal' );
like( $@, qr/^oopsie at /, 'die in finally{} does not corrupt $@' );
like( $warnings, qr/double oops at /, 'die in finally{} warns inner exception' );
}
done_testing;

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#!/usr/bin/perl
use v5.14;
use warnings;
use Test::More;
use Syntax::Keyword::Try;
# try/catch localises $@ (RT118415)
{
eval { die "oopsie" };
like( $@, qr/^oopsie at /, '$@ before try/catch' );
try { die "another failure" } catch ($e) {}
like( $@, qr/^oopsie at /, '$@ after try/catch' );
}
done_testing;

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#!/usr/bin/perl
use v5.14;
use warnings;
use Test::More;
use Syntax::Keyword::Try;
# wantarray inside try
{
my $context;
sub whatcontext
{
try {
$context = wantarray ? "list" :
defined wantarray ? "scalar" : "void";
}
catch ($e) { }
}
whatcontext();
is($context, "void", 'sub {try} in void');
my $scalar = whatcontext();
is($context, "scalar", 'sub {try} in scalar');
my @array = whatcontext();
is($context, "list", 'sub {try} in list');
}
done_testing;

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#!/usr/bin/perl
use v5.14;
use warnings;
use Test::More;
use Syntax::Keyword::Try;
# try as final expression yields correct value
{
my $scalar = do {
try { 123 }
catch ($e) { 456 }
};
is($scalar, 123, 'do { try } in scalar context');
my @list = do {
try { 1, 2, 3 }
catch ($e) { 4, 5, 6 }
};
is_deeply(\@list, [1, 2, 3], 'do { try } in list context');
}
# catch as final expression yields correct value
{
my $scalar = do {
try { die "Oops" }
catch ($e) { 456 }
};
is($scalar, 456, 'do { try/catch } in scalar context');
my @list = do {
try { die "Oops" }
catch ($e) { 4, 5, 6 }
};
is_deeply(\@list, [4, 5, 6], 'do { try/catch } in list context');
$scalar = do {
try { die "Oops" }
catch ($e) { my $x = 123; 456 }
};
is($scalar, 456, 'do { try/catch } with multiple statements');
}
done_testing;

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#!/usr/bin/perl
use v5.14;
use warnings;
use Test::More;
use Syntax::Keyword::Try;
# forbidding finally
{
use Syntax::Keyword::Try '-no_finally';
ok( !defined eval <<'EOPERL',
try { 123 }
finally { 456 }
EOPERL
'try/finally is forbidden' );
like( $@, qr/^finally \{\} is not permitted here / );
}
# require var
{
use Syntax::Keyword::Try '-require_var';
ok( !defined eval <<'EOPERL',
try { 123 }
catch { 456 }
EOPERL
'try/catch requires var' );
like( $@, qr/^Expected \(VAR\) for catch / );
}
done_testing;

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#!/usr/bin/perl
use v5.14;
use warnings;
use Test::More;
use Syntax::Keyword::Try;
use Syntax::Keyword::Try::Deparse;
use B::Deparse;
my $deparser = B::Deparse->new();
sub is_deparsed
{
my ( $sub, $exp, $name ) = @_;
my $got = $deparser->coderef2text( $sub );
# Deparsed output is '{ ... }'-wrapped
$got = ( $got =~ m/^{\n(.*)\n}$/s )[0];
$got =~ s/^ //mg;
# Deparsed output will have a lot of pragmata and so on
1 while $got =~ s/^\s*(?:use|no) \w+.*\n//;
$got =~ s/^BEGIN \{\n.*?\n\}\n//s;
# Trim a trailing linefeed
chomp $got;
is( $got, $exp, $name );
}
is_deparsed
sub { try { ABC() } catch { DEF() } },
"try {\n ABC();\n}\ncatch {\n DEF();\n}",
'try/catch';
is_deparsed
sub { try { ABC() } catch($e) { DEF() } },
"try {\n ABC();\n}\ncatch {\n my \$e = \$@;\n DEF();\n}",
'try/catch(VAR)';
is_deparsed
sub { try { ABC() } finally { XYZ() } },
"try {\n ABC();\n}\nfinally {\n XYZ();\n}",
'try/finally';
is_deparsed
sub { try { ABC() } catch { DEF() } finally { XYZ() } },
"try {\n ABC();\n}\ncatch {\n DEF();\n}\nfinally {\n XYZ();\n}",
'try/catch/finally';
done_testing;

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#!/usr/bin/perl
use v5.14;
use warnings;
use Test::More;
BEGIN {
plan skip_all => "Future is not available"
unless eval { require Future };
plan skip_all => "Future::AsyncAwait >= 0.50 is not available"
unless eval { require Future::AsyncAwait;
Future::AsyncAwait->VERSION( '0.50' ) };
plan skip_all => "Syntax::Keyword::Try >= 0.22 is not available"
unless eval { require Syntax::Keyword::Try;
Syntax::Keyword::Try->VERSION( '0.22' ) };
Future::AsyncAwait->import;
Syntax::Keyword::Try->import;
diag( "Future::AsyncAwait $Future::AsyncAwait::VERSION, " .
"Syntax::Keyword::Try $Syntax::Keyword::Try::VERSION" );
}
# await in try/catch
{
async sub with_trycatch
{
my $f = shift;
my $ret;
try {
await $f;
$ret = "result";
}
catch ($e) {
$ret = "oopsie";
}
return $ret;
}
my $f1 = Future->new;
my $fdone = with_trycatch( $f1 );
$f1->done;
is( scalar $fdone->get, "result", '$fdone for successful await in try/catch' );
my $f2 = Future->new;
my $ffail = with_trycatch( $f2 );
$f2->fail( "fail" );
is( scalar $ffail->get, "oopsie", '$ffail for failed await in try/catch' );
}
# await in try/catch with return
{
my $fellthrough;
async sub with_trycatch_return
{
my $f = shift;
try {
await $f;
return "result";
}
catch ($e) {}
$fellthrough++;
return "fallthrough";
}
my $f1 = Future->new;
my $fdone = with_trycatch_return( $f1 );
$f1->done;
is( scalar $fdone->get, "result", '$fdone for successful await in try/catch with return' );
ok( !$fellthrough, 'fallthrough after try{return} did not happen' );
}
# await in try/catch list context (RT134790)
{
async sub return_list { return ( "first", "second" ); }
async sub await_return_list
{
try {
return await return_list();
}
catch ($e) { die $e; }
}
my ( $r1, $r2 ) = await await_return_list();
is( $r1, "first", 'first result from try/return list' );
is( $r2, "second", 'second result from try/return list' );
}
# await in try/finally
{
async sub with_tryfinally
{
my $f = shift;
my $ret = "";
try {
await $f;
$ret .= "T";
}
finally {
$ret .= "F";
}
return $ret;
}
my $f1 = Future->new;
my $fret = with_tryfinally( $f1 );
$f1->done;
is( scalar $fret->get, "TF", '$fret for await in try/finally' );
}
# finally still runs for cancel (RT135351)
{
my $ok;
my $f1 = Future->new;
my $fret = (async sub {
try {
await $f1;
}
finally {
$ok++;
}
})->();
ok( !$ok, 'defer {} not run before ->cancel' );
$fret->cancel;
ok( $ok, 'defer {} was run after ->cancel' );
}
# await in toplevel try
{
try {
is( await Future->done( "success" ), "success",
'await in toplevel try' );
}
catch {
fail( 'await in toplevel try' );
}
try {
await Future->fail( "failure\n" );
}
catch ( $e ) {
is( $e, "failure\n", 'await in toplevel try/catch failure' );
}
}
done_testing;

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#!/usr/bin/perl
use v5.14;
use warnings;
use Test::More;
BEGIN {
plan skip_all => "Syntax::Keyword::Defer >= 0.02 is not available"
unless eval { require Syntax::Keyword::Defer;
Syntax::Keyword::Defer->VERSION( '0.02' ) };
plan skip_all => "Syntax::Keyword::Try >= 0.18 is not available"
unless eval { require Syntax::Keyword::Try;
Syntax::Keyword::Try->VERSION( '0.18' ) };
Syntax::Keyword::Defer->import;
Syntax::Keyword::Try->import;
diag( "Syntax::Keyword::Defer $Syntax::Keyword::Defer::VERSION, " .
"Syntax::Keyword::Try $Syntax::Keyword::Try::VERSION" );
}
# defer inside try
{
my $ok;
try {
defer { $ok .= "2" }
$ok .= "1";
}
catch ($e) { }
is( $ok, "12", 'defer inside try' );
}
# defer inside catch
{
my $ok;
try {
die "Oopsie\n";
}
catch ($e) {
defer { $ok .= "4" }
$ok .= "3";
}
is( $ok, "34", 'defer inside catch' );
}
# try/catch inside defer
{
my $ok;
{
defer {
try { $ok .= "6" }
catch ($e) {}
}
$ok .= "5";
}
is( $ok, "56", 'try/catch inside defer' );
}
done_testing;

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#!/usr/bin/perl
use v5.14;
use warnings;
use Test::More;
# RT123547 observes that if S:K:T is loaded late after multiple threads
# are actually started, it will crash
BEGIN {
eval { require threads; threads->import; 1 } or
plan skip_all => "threads are not supported";
}
# Start two threads doing the same thing concurrently and hope we get
# to the end
my @threads = map {
threads->create( sub {
my $x;
# We have to late-load the module and then demonstrate that it works
# Because of late loading we couldn't have written normal code here, so
# we'll string-eval it
eval <<'EOPERL'
use Syntax::Keyword::Try;
try {
$x = "a";
die "oops";
}
catch ($e) {
$x .= "b";
}
finally {
$x .= "c";
}
1;
EOPERL
or die "Failed - $@";
return $x;
} );
} 1 .. 2;
is( $_->join, "abc", 'try/catch/finally correct result' ) for @threads;
pass "Did not crash";
done_testing;

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#!/usr/bin/perl
use v5.14;
use warnings;
use Test::More;
use Syntax::Keyword::Try;
sub inner
{
my $canary = Canary->new; # if this line is commented, nothing happens
try {
return 123;
}
catch ($e) {
die "Something terrible happened: $e";
}
}
sub outer
{
my @result;
try {
@result = (1, scalar inner()); # scalar or void context is mandatory
1; # or catch will be triggered
}
catch ($e) {
die "Something terrible happened: $e";
}
return @result;
}
is_deeply [ outer() ], [ 1, 123 ], "No extra data in return";
done_testing;
package Canary;
sub new {
bless {}, shift;
}
sub DESTROY {
my $x; # Destructor MUST be nonempty
$@ = "oops"; # Assigning to $@ is optional
}

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#!/usr/bin/perl
use v5.14;
use warnings;
use Test::More;
eval "use Test::Pod 1.00";
plan skip_all => "Test::Pod 1.00 required for testing POD" if $@;
all_pod_files_ok();