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m4: readline: Use pkg-config where possible 

With the 7.0 release, readline has finally started shipping
pkg-config support in the form of a readline.pc file.

Unfortunately, most downstreams have yet to catch up with this
change: among Linux distributions in particular, Fedora Rawhide
seems to be the only one installing it at the moment.

Non-Linux operating systems have been faring much better in
this regard: both FreeBSD (through ports) and macOS (through
homebrew) include pkg-config support in their readline package.

This is great news for us, since those are the platforms where
pkg-config is more useful on account of them installing headers
and libraries outside of the respective default search paths.

Our implementation checks whether readline is registered as a
pkg-config package, and if so obtains CFLAGS and LIBS using the
tool; if not, we just keep using the existing logic.

This commit is best viewed with 'git show -w'.

Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
This commit is contained in:
Andrea Bolognani 2019-04-02 12:32:11 +02:00
parent c6921fd0be
commit c98de2173e
1 changed files with 27 additions and 18 deletions
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45
m4/virt-readline.m4
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@ -23,27 +23,36 @@ AC_DEFUN([LIBVIRT_ARG_READLINE],[
AC_DEFUN([LIBVIRT_CHECK_READLINE],[
# This function is present in all reasonable (5.0+) readline versions;
# however, the macOS base system contains a library called libedit which
# takes over the readline name despite lacking many of its features. We
# want to make sure we only enable readline support when linking against
# the actual readline library, and the availability of this specific
# functions is as good a witness for that fact as any.
AC_CHECK_DECLS([rl_completion_quote_character],
[], [],
[[#include <stdio.h>
#include <readline/readline.h>]])
# We have to check for readline.pc's presence beforehand because for
# the longest time the library didn't ship a .pc file at all
PKG_CHECK_EXISTS([readline], [use_pkgconfig=1], [use_pkgconfig=0])
if test "$ac_cv_have_decl_rl_completion_quote_character" = "no" ; then
if test "$with_readline" = "yes" ; then
AC_MSG_ERROR([readline is missing rl_completion_quote_character])
else
with_readline=no;
if test $use_pkgconfig = 1; then
# readline 7.0 is the first version which includes pkg-config support
LIBVIRT_CHECK_PKG([READLINE], [readline], [7.0])
else
# This function is present in all reasonable (5.0+) readline versions;
# however, the macOS base system contains a library called libedit which
# takes over the readline name despite lacking many of its features. We
# want to make sure we only enable readline support when linking against
# the actual readline library, and the availability of this specific
# functions is as good a witness for that fact as any.
AC_CHECK_DECLS([rl_completion_quote_character],
[], [],
[[#include <stdio.h>
#include <readline/readline.h>]])
if test "$ac_cv_have_decl_rl_completion_quote_character" = "no" ; then
if test "$with_readline" = "yes" ; then
AC_MSG_ERROR([readline is missing rl_completion_quote_character])
else
with_readline=no;
fi
fi
fi
# The normal library check...
LIBVIRT_CHECK_LIB([READLINE], [readline], [readline], [readline/readline.h])
# The normal library check...
LIBVIRT_CHECK_LIB([READLINE], [readline], [readline], [readline/readline.h])
fi
# We need this to avoid compilation issues with modern compilers.
# See 9ea3424a178 for a more detailed explanation