Hi,


Asan has detected a memory leak :

$ wget https://github.com/python/cpython/archive/v3.9.2.tar.gz
$ tar xvf v3.9.2.tar.gz
$ ./configure --disable-shared CFLAGS="-fsanitize=address -ggdb" CXXFLAGS="-fsanitize=address -ggdb" LDFLAGS="-fsanitize=address"
$ make -j4
$ ~/cpython-3.9.2# ./python -E -S -m sysconfig --generate-posix-vars

=================================================================
==330505==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 300082 byte(s) in 137 object(s) allocated from:
    #0 0x7f647a692bc8 in malloc (/lib/x86_64-linux-gnu/libasan.so.5+0x10dbc8)
    #1 0x55a58e972015 in PyMem_RawMalloc Objects/obmalloc.c:572
    #2 0x55a58e972015 in _PyObject_Malloc Objects/obmalloc.c:1645
    #3 0x55a58e972015 in _PyObject_Malloc Objects/obmalloc.c:1638

Direct leak of 2066 byte(s) in 2 object(s) allocated from:
    #0 0x7f647a692ffe in __interceptor_realloc (/lib/x86_64-linux-gnu/libasan.so.5+0x10dffe)
    #1 0x55a58e9c9e7d in resize_compact Objects/unicodeobject.c:1079

Direct leak of 672 byte(s) in 1 object(s) allocated from:
    #0 0x7f647a692ffe in __interceptor_realloc (/lib/x86_64-linux-gnu/libasan.so.5+0x10dffe)
    #1 0x55a58eb6c620 in _PyObject_GC_Resize Modules/gcmodule.c:2297

Indirect leak of 110001 byte(s) in 115 object(s) allocated from:
    #0 0x7f647a692bc8 in malloc (/lib/x86_64-linux-gnu/libasan.so.5+0x10dbc8)
    #1 0x55a58e972015 in PyMem_RawMalloc Objects/obmalloc.c:572
    #2 0x55a58e972015 in _PyObject_Malloc Objects/obmalloc.c:1645
    #3 0x55a58e972015 in _PyObject_Malloc Objects/obmalloc.c:1638

Indirect leak of 536 byte(s) in 1 object(s) allocated from:
    #0 0x7f647a692bc8 in malloc (/lib/x86_64-linux-gnu/libasan.so.5+0x10dbc8)
    #1 0x55a58e972382 in _PyObject_Malloc Objects/obmalloc.c:572
    #2 0x55a58e972382 in pymalloc_realloc Objects/obmalloc.c:1988
    #3 0x55a58e972382 in _PyObject_Realloc Objects/obmalloc.c:2007

SUMMARY: AddressSanitizer: 413357 byte(s) leaked in 256 allocation(s).


Thanks,
Ramin

To run the address sanitizer you need to deactivate pymalloc and pass some of the asan flags to avoid false positives. Check our our buildbot configuration for it:

https://github.com/python/buildmaster-config/blob/master/master/custom/factories.py#L223

This looks like a false positive to me.