valgrind reports memory still reachable, allocated by libglib
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Does this valgrind report present a possible memory leak and is there anything that can be done to get valgrind to instead report that all heap blocks are freed?
main.cpp:
#include <QTemporaryDir> int main() { QTemporaryDir d; }Build steps:
/usr/bin/c++ -fPIC -DQT_DISABLE_DEPRECATED_BEFORE=0x050F00 -g -std=gnu++17 -isystem /home/sdhiker/Qt/6.2.0/gcc_64/include/QtCore -isystem /home/sdhiker/Qt/6.2.0/gcc_64/include -isystem /home/sdhiker/Qt/6.2.0/gcc_64/mkspecs/linux-g++ -o main.o -c main.cpp /usr/bin/c++ -g main.o -Wl,-rpath,/home/sdhiker/Qt/6.2.0/gcc_64/lib /home/sdhiker/Qt/6.2.0/gcc_64/lib/libQt6Core.so.6.2.0Program execution and valgrind report:
λ valgrind --leak-check=full --show-leak-kinds=all ./a.out ==22265== Memcheck, a memory error detector ==22265== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al. ==22265== Using Valgrind-3.15.0 and LibVEX; rerun with -h for copyright info ==22265== Command: ./a.out ==22265== ==22265== ==22265== HEAP SUMMARY: ==22265== in use at exit: 18,612 bytes in 6 blocks ==22265== total heap usage: 63 allocs, 57 frees, 135,817 bytes allocated ==22265== ==22265== 4 bytes in 1 blocks are still reachable in loss record 1 of 6 ==22265== at 0x483B7F3: malloc (in /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so) ==22265== by 0x73588E3: ??? (in /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0.6400.6) ==22265== by 0x7358F03: g_private_get (in /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0.6400.6) ==22265== by 0x732A460: g_slice_alloc (in /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0.6400.6) ==22265== by 0x72F92E1: g_hash_table_new_full (in /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0.6400.6) ==22265== by 0x731C7C2: ??? (in /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0.6400.6) ==22265== by 0x4011B89: call_init.part.0 (dl-init.c:72) ==22265== by 0x4011C90: call_init (dl-init.c:30) ==22265== by 0x4011C90: _dl_init (dl-init.c:119) ==22265== by 0x4001139: ??? (in /usr/lib/x86_64-linux-gnu/ld-2.31.so) ==22265== ==22265== 32 bytes in 1 blocks are still reachable in loss record 2 of 6 ==22265== at 0x483DD99: calloc (in /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so) ==22265== by 0x7311EF0: g_malloc0 (in /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0.6400.6) ==22265== by 0x72F802F: ??? (in /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0.6400.6) ==22265== by 0x72F9320: g_hash_table_new_full (in /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0.6400.6) ==22265== by 0x731C7C2: ??? (in /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0.6400.6) ==22265== by 0x4011B89: call_init.part.0 (dl-init.c:72) ==22265== by 0x4011C90: call_init (dl-init.c:30) ==22265== by 0x4011C90: _dl_init (dl-init.c:119) ==22265== by 0x4001139: ??? (in /usr/lib/x86_64-linux-gnu/ld-2.31.so) ==22265== ==22265== 64 bytes in 1 blocks are still reachable in loss record 3 of 6 ==22265== at 0x483B723: malloc (in /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so) ==22265== by 0x483E017: realloc (in /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so) ==22265== by 0x7311F3F: g_realloc (in /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0.6400.6) ==22265== by 0x72F801A: ??? (in /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0.6400.6) ==22265== by 0x72F9320: g_hash_table_new_full (in /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0.6400.6) ==22265== by 0x731C7C2: ??? (in /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0.6400.6) ==22265== by 0x4011B89: call_init.part.0 (dl-init.c:72) ==22265== by 0x4011C90: call_init (dl-init.c:30) ==22265== by 0x4011C90: _dl_init (dl-init.c:119) ==22265== by 0x4001139: ??? (in /usr/lib/x86_64-linux-gnu/ld-2.31.so) ==22265== ==22265== 96 bytes in 1 blocks are still reachable in loss record 4 of 6 ==22265== at 0x483B7F3: malloc (in /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so) ==22265== by 0x7311E98: g_malloc (in /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0.6400.6) ==22265== by 0x732A485: g_slice_alloc (in /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0.6400.6) ==22265== by 0x72F92E1: g_hash_table_new_full (in /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0.6400.6) ==22265== by 0x731C7C2: ??? (in /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0.6400.6) ==22265== by 0x4011B89: call_init.part.0 (dl-init.c:72) ==22265== by 0x4011C90: call_init (dl-init.c:30) ==22265== by 0x4011C90: _dl_init (dl-init.c:119) ==22265== by 0x4001139: ??? (in /usr/lib/x86_64-linux-gnu/ld-2.31.so) ==22265== ==22265== 2,032 bytes in 1 blocks are still reachable in loss record 5 of 6 ==22265== at 0x483DD99: calloc (in /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so) ==22265== by 0x7311EF0: g_malloc0 (in /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0.6400.6) ==22265== by 0x7335B65: ??? (in /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0.6400.6) ==22265== by 0x732A6D2: g_slice_alloc (in /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0.6400.6) ==22265== by 0x72F92E1: g_hash_table_new_full (in /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0.6400.6) ==22265== by 0x731C7C2: ??? (in /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0.6400.6) ==22265== by 0x4011B89: call_init.part.0 (dl-init.c:72) ==22265== by 0x4011C90: call_init (dl-init.c:30) ==22265== by 0x4011C90: _dl_init (dl-init.c:119) ==22265== by 0x4001139: ??? (in /usr/lib/x86_64-linux-gnu/ld-2.31.so) ==22265== ==22265== 16,384 bytes in 1 blocks are still reachable in loss record 6 of 6 ==22265== at 0x483B7F3: malloc (in /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so) ==22265== by 0x7311E98: g_malloc (in /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0.6400.6) ==22265== by 0x731C7D3: ??? (in /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0.6400.6) ==22265== by 0x4011B89: call_init.part.0 (dl-init.c:72) ==22265== by 0x4011C90: call_init (dl-init.c:30) ==22265== by 0x4011C90: _dl_init (dl-init.c:119) ==22265== by 0x4001139: ??? (in /usr/lib/x86_64-linux-gnu/ld-2.31.so) ==22265== ==22265== LEAK SUMMARY: ==22265== definitely lost: 0 bytes in 0 blocks ==22265== indirectly lost: 0 bytes in 0 blocks ==22265== possibly lost: 0 bytes in 0 blocks ==22265== still reachable: 18,612 bytes in 6 blocks ==22265== suppressed: 0 bytes in 0 blocks ==22265== ==22265== For lists of detected and suppressed errors, rerun with: -s ==22265== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0) -
Don't see anything Qt can do against this. Also not a "memleak" which you should take care of. Looks like some init stuff for glib. You should ask the glib developers if you want to get it fixed.
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what does "still reachable mean?" If I had to guess, I would think it means that nothing in the heap manager has invalidated the content of those blocks following deltion...as I would expect upon program exit.
Deletion simply marks the blocks as reusable. It doesn't overwrite the data in them.
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Don't see anything Qt can do against this. Also not a "memleak" which you should take care of. Looks like some init stuff for glib. You should ask the glib developers if you want to get it fixed.
