[Python-Dev] cpython: Issue #18408: Fix PyUnicode_AsUTF8AndSize(), raise MemoryError exception on

[Victor Stinner]

2013/10/29 Georg Brandl <g.brandl at gmx.net>:
>> diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
>> --- a/Objects/unicodeobject.c
>> +++ b/Objects/unicodeobject.c
>> @@ -3766,6 +3766,7 @@
>>              return NULL;
>>          _PyUnicode_UTF8(unicode) = PyObject_MALLOC(PyBytes_GET_SIZE(bytes) + 1);
>>          if (_PyUnicode_UTF8(unicode) == NULL) {
>> +            PyErr_NoMemory();
>>              Py_DECREF(bytes);
>>              return NULL;
>>          }
>
> Shouldn't this (and related commits from #18408) have been committed to the 3.3
> branch?

All changes of #18408 "should" be backported, but I don't plan to
backport them. It is not trivial to backport them. Nobody complained
before (memory allocation failure are usually bad handled anyway, it
will crash later if it does not crash here). And I'm not 100%
confident that these changes would not break anything.

Examples of possible regression:

- PyEval_GetLocals() now raises an exception in case of an error. This
change "should" not break anything, because callers were already
raising an exception when PyEval_GetLocals() returns NULL. The builtin
locals() function was not raising an exception in case of error, but
it's probably because it is very unlikely that the function is called
without any frame (PyEval_GetFrame(); returns NULL).

- many functions now fail with an assertion error when they are called
with an exception set (assert(!PyErr_Occurred());) because they may
replace the exception without noticing the caller

- I tried to check reference counters, but I may have introduce a
regression leak in the error handling code

If there is really a regression, I prefer to limit it to the new
version, not to a stable version.

Note: I'm not saying that I'm 0% confident in my changes :-)

Victor