When ValueError is raised if an integer is larger than the limit,
mention sys.set_int_max_str_digits() in the error message.
(cherry picked from commit e841ffc915)
Co-authored-by: Ned Deily <nad@python.org>
* Correctly pre-check for int-to-str conversion (#96537)
Converting a large enough `int` to a decimal string raises `ValueError` as expected. However, the raise comes _after_ the quadratic-time base-conversion algorithm has run to completion. For effective DOS prevention, we need some kind of check before entering the quadratic-time loop. Oops! =)
The quick fix: essentially we catch _most_ values that exceed the threshold up front. Those that slip through will still be on the small side (read: sufficiently fast), and will get caught by the existing check so that the limit remains exact.
The justification for the current check. The C code check is:
```c
max_str_digits / (3 * PyLong_SHIFT) <= (size_a - 11) / 10
```
In GitHub markdown math-speak, writing $M$ for `max_str_digits`, $L$ for `PyLong_SHIFT` and $s$ for `size_a`, that check is:
$$\left\lfloor\frac{M}{3L}\right\rfloor \le \left\lfloor\frac{s - 11}{10}\right\rfloor$$
From this it follows that
$$\frac{M}{3L} < \frac{s-1}{10}$$
hence that
$$\frac{L(s-1)}{M} > \frac{10}{3} > \log_2(10).$$
So
$$2^{L(s-1)} > 10^M.$$
But our input integer $a$ satisfies $|a| \ge 2^{L(s-1)}$, so $|a|$ is larger than $10^M$. This shows that we don't accidentally capture anything _below_ the intended limit in the check.
<!-- gh-issue-number: gh-95778 -->
* Issue: gh-95778
<!-- /gh-issue-number -->
Co-authored-by: Gregory P. Smith [Google LLC] <greg@krypto.org>
Co-authored-by: Christian Heimes <christian@python.org>
Co-authored-by: Mark Dickinson <dickinsm@gmail.com>
(cherry picked from commit 5924243199)
Co-authored-by: Mark Dickinson <mdickinson@enthought.com>
Co-authored-by: Mark Dickinson <mdickinson@enthought.com>
* bpo-37986: Improve perfomance of PyLong_FromDouble()
* Use strict bound check for safety and symmetry
* Remove possibly outdated performance claims
Co-authored-by: Mark Dickinson <dickinsm@gmail.com>
The bulk of this patch was generated automatically with:
for name in \
PyObject_Vectorcall \
Py_TPFLAGS_HAVE_VECTORCALL \
PyObject_VectorcallMethod \
PyVectorcall_Function \
PyObject_CallOneArg \
PyObject_CallMethodNoArgs \
PyObject_CallMethodOneArg \
;
do
echo $name
git grep -lwz _$name | xargs -0 sed -i "s/\b_$name\b/$name/g"
done
old=_PyObject_FastCallDict
new=PyObject_VectorcallDict
git grep -lwz $old | xargs -0 sed -i "s/\b$old\b/$new/g"
and then cleaned up:
- Revert changes to in docs & news
- Revert changes to backcompat defines in headers
- Nudge misaligned comments
Each Python subinterpreter now has its own "small integer
singletons": numbers in [-5; 257] range.
It is no longer possible to change the number of small integers at
build time by overriding NSMALLNEGINTS and NSMALLPOSINTS macros:
macros should now be modified manually in pycore_pystate.h header
file.
For now, continue to share _PyLong_Zero and _PyLong_One singletons
between all subinterpreters.
bpo-37802, bpo-38321: Fix the following warnings:
longobject.c(420): warning C4244: 'function': conversion from
'unsigned __int64' to 'sdigit', possible loss of data
longobject.c(428): warning C4267: 'function': conversion from
'size_t' to 'sdigit', possible loss of data
* Split _Py_InitializeCore_impl() into subfunctions: add multiple pycore_init_xxx() functions
* Preliminary sys.stderr is now set earlier to get an usable
sys.stderr ealier.
* Move code into _Py_Initialize_ReconfigureCore() to be able to call
it from _Py_InitializeCore().
* Split _PyExc_Init(): create a new _PyBuiltins_AddExceptions()
function.
* Call _PyExc_Init() earlier in _Py_InitializeCore_impl()
and new_interpreter() to get working exceptions earlier.
* _Py_ReadyTypes() now returns _PyInitError rather than calling
Py_FatalError().
* Misc code cleanup
Configuring python with ./configure --with-pydebug CFLAGS="-D COUNT_ALLOCS -O0"
makes "make smelly" fail as some symbols were being exported without the "Py_" or
"_Py" prefixes.
* Convert PyObject_INIT() and PyObject_INIT_VAR() macros to static
inline functions.
* Fix usage of these functions: cast to PyObject* or PyVarObject*.
METH_NOARGS functions need only a single argument but they are cast
into a PyCFunction, which takes two arguments. This triggers an
invalid function cast warning in gcc8 due to the argument mismatch.
Fix this by adding a dummy unused argument.
Explicitly cast digits (Py_ssize_t) to double to fix the following
false-alarm warning from Coverity:
"fsize_z = digits * log_base_BASE[base] + 1;"
CID 1424951: Incorrect expression (UNINTENDED_INTEGER_DIVISION)
Dividing integer expressions "9223372036854775783UL" and "4UL", and
then converting the integer quotient to type "double". Any remainder,
or fractional part of the quotient, is ignored.
Victor Stinner