Example on Python 3.12 when loading _crypt extension module:
$ PYTHONMALLOC=malloc valgrind --leak-check=full --show-leak-kinds=all --num-callers=50 ./python -c 'import _crypt'
==2444751== Memcheck, a memory error detector
==2444751== Copyright (C) 2002-2024, and GNU GPL'd, by Julian Seward et al.
==2444751== Using Valgrind-3.23.0 and LibVEX; rerun with -h for copyright info
==2444751== Command: ./python -c import\ _crypt
==2444751==
==2444751==
==2444751== HEAP SUMMARY:
==2444751== in use at exit: 3,253 bytes in 8 blocks
==2444751== total heap usage: 44,037 allocs, 44,029 frees, 6,464,804 bytes allocated
==2444751==
==2444751== 21 bytes in 1 blocks are still reachable in loss record 1 of 7
==2444751== at 0x484282F: malloc (vg_replace_malloc.c:446)
==2444751== by 0x402587F: malloc (rtld-malloc.h:56)
==2444751== by 0x402587F: strdup (strdup.c:42)
==2444751== by 0x4014B58: _dl_load_cache_lookup (dl-cache.c:515)
==2444751== by 0x4008F1F: _dl_map_object (dl-load.c:2116)
==2444751== by 0x400287C: openaux (dl-deps.c:64)
==2444751== by 0x4001522: _dl_catch_exception (dl-catch.c:237)
==2444751== by 0x4002CDF: _dl_map_object_deps (dl-deps.c:232)
==2444751== by 0x400CA34: dl_open_worker_begin (dl-open.c:638)
==2444751== by 0x4001522: _dl_catch_exception (dl-catch.c:237)
==2444751== by 0x400C10F: dl_open_worker (dl-open.c:803)
==2444751== by 0x4001522: _dl_catch_exception (dl-catch.c:237)
==2444751== by 0x400C563: _dl_open (dl-open.c:905)
==2444751== by 0x49E9E23: dlopen_doit (dlopen.c:56)
==2444751== by 0x4001522: _dl_catch_exception (dl-catch.c:237)
==2444751== by 0x4001678: _dl_catch_error (dl-catch.c:256)
==2444751== by 0x49E9912: _dlerror_run (dlerror.c:138)
==2444751== by 0x49E9EDE: dlopen_implementation (dlopen.c:71)
==2444751== by 0x49E9EDE: dlopen@@GLIBC_2.34 (dlopen.c:81)
==2444751== (...)
Valgrind reports leaks on memory allocated by dlopen() in Python/dynload_shlib.c, because Python doesn't call dlclose().
I don't think that it's big deal to not call dlclose(), since there is little memory and it's not common to unload a dynamic library at runtime. Also, I don't see where/how dlclose() can be called.
Instead, I propose to suppress these warnings in the Valgrind suppressions file, to help spotting more important leaks.
Linked PRs
Example on Python 3.12 when loading
_cryptextension module:Valgrind reports leaks on memory allocated by
dlopen()inPython/dynload_shlib.c, because Python doesn't calldlclose().I don't think that it's big deal to not call
dlclose(), since there is little memory and it's not common to unload a dynamic library at runtime. Also, I don't see where/howdlclose()can be called.Instead, I propose to suppress these warnings in the Valgrind suppressions file, to help spotting more important leaks.
Linked PRs