Stefan Krah <[email protected]> added the comment:
I've verified the leak manually. The cause is that global variables in
unicodeobject.c, e.g. free_list, are used before _PyUnicode_Init() is
called. Later on _PyUnicode_Init() sets these variables to NULL, losing
the allocated memory.
Here is an example of the earliest use of free_list during
_Py_ReadyTypes (),
well before _PyUnicode_Init():
Breakpoint 1, unicode_dealloc (unicode=0x1b044c0) at Objects/unicodeobject.c:392
392 switch (PyUnicode_CHECK_INTERNED(unicode)) {
(gdb) bt
#0 unicode_dealloc (unicode=0x1b044c0) at Objects/unicodeobject.c:392
#1 0x000000000044fc69 in PyUnicode_InternInPlace (p=0x7fff303852b8) at
Objects/unicodeobject.c:9991
#2 0x000000000044fed3 in PyUnicode_InternFromString (cp=0x568861 "__len__") at
Objects/unicodeobject.c:10025
#3 0x00000000004344d0 in init_slotdefs () at Objects/typeobject.c:5751
#4 0x0000000000434840 in add_operators (type=0x7be260) at
Objects/typeobject.c:5905
#5 0x000000000042eec8 in PyType_Ready (type=0x7be260) at
Objects/typeobject.c:3810
#6 0x000000000042edfc in PyType_Ready (type=0x7bde60) at
Objects/typeobject.c:3774
#7 0x000000000041aa5f in _Py_ReadyTypes () at Objects/object.c:1514
#8 0x00000000004992ff in Py_InitializeEx (install_sigs=1) at
Python/pythonrun.c:232
#9 0x000000000049957f in Py_Initialize () at Python/pythonrun.c:321
#10 0x00000000004b289f in Py_Main (argc=1, argv=0x1afa010) at Modules/main.c:590
#11 0x0000000000417dcc in main (argc=1, argv=0x7fff30385758) at
./Modules/python.c:59
(gdb) n
411 if (PyUnicode_CheckExact(unicode) &&
(gdb)
414 if (unicode->length >= KEEPALIVE_SIZE_LIMIT) {
(gdb)
419 if (unicode->defenc) {
(gdb)
423 *(PyUnicodeObject **)unicode = free_list;
(gdb) n
424 free_list = unicode;
(gdb) n
425 numfree++;
(gdb) n
411 if (PyUnicode_CheckExact(unicode) &&
A possible fix could be to initialize the globals right at the start
in main.c. Note that there are still several Unicode API functions in
main.c before PyType_Ready has been called on the Unicode type.
With the patch, Valgrind does not show the leak any longer.
----------
keywords: +patch
priority: normal -> high
stage: -> patch review
title: Memory leak (r70459) -> Initialization of globals in unicodeobject.c
Added file: http://bugs.python.org/file19336/unicode_init_globals.patch
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<http://bugs.python.org/issue10156>
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