Valgrind shows memory leak with empty main without including headers - c++

Question

Lubuntu 15.10
I have project with memory leaks. I can find them, so I cleaned up my main.cpp file, and now it looks like this:
int main()
{
return 0;
}
When I check memory with the command:
valgrind --leak-check=full --show-leak-kinds=all ./MyProgram > log1.txt 2>&1
I got these errors:
==5219==
==5219== LEAK SUMMARY:
==5219== definitely lost: 0 bytes in 0 blocks
==5219== indirectly lost: 0 bytes in 0 blocks
==5219== possibly lost: 728 bytes in 18 blocks
==5219== still reachable: 44,676 bytes in 224 blocks
==5219== of which reachable via heuristic:
==5219== newarray : 832 bytes in 16 blocks
==5219== suppressed: 0 bytes in 0 blocks
==5219==
==5219== For counts of detected and suppressed errors, rerun with: -v
==5219== ERROR SUMMARY: 18 errors from 18 contexts (suppressed: 0 from 0)
Some of the errors were:
==5219== 2,048 bytes in 1 blocks are still reachable in loss record 240 of 242
==5219== at 0x402E2EC: realloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
==5219== by 0x5F7C151: g_realloc (in /lib/i386-linux-gnu/libglib-2.0.so.0.4600.2)
==5219== by 0x5F06BCB: g_value_register_transform_func (in /usr/lib/i386-linux-gnu/libgobject-2.0.so.0.4600.2)
==5219== by 0x5F08D6A: ??? (in /usr/lib/i386-linux-gnu/libgobject-2.0.so.0.4600.2)
==5219== by 0x5ED9A2D: ??? (in /usr/lib/i386-linux-gnu/libgobject-2.0.so.0.4600.2)
==5219== by 0x400EDCF: call_init.part.0 (dl-init.c:72)
==5219== by 0x400EEDF: call_init (dl-init.c:30)
==5219== by 0x400EEDF: _dl_init (dl-init.c:120)
==5219== by 0x4000ACE: ??? (in /lib/i386-linux-gnu/ld-2.21.so)
==5219== 8 bytes in 1 blocks are possibly lost in loss record 95 of 242
==5219== at 0x402E0D8: calloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
==5219== by 0x5F7C0DA: g_malloc0 (in /lib/i386-linux-gnu/libglib-2.0.so.0.4600.2)
==5219== by 0x5EFC587: ??? (in /usr/lib/i386-linux-gnu/libgobject-2.0.so.0.4600.2)
==5219== by 0x5F011B8: g_type_register_fundamental (in /usr/lib/i386-linux-gnu/libgobject-2.0.so.0.4600.2)
==5219== by 0x5EE929E: ??? (in /usr/lib/i386-linux-gnu/libgobject-2.0.so.0.4600.2)
==5219== by 0x5ED9A1E: ??? (in /usr/lib/i386-linux-gnu/libgobject-2.0.so.0.4600.2)
==5219== by 0x400EDCF: call_init.part.0 (dl-init.c:72)
==5219== by 0x400EEDF: call_init (dl-init.c:30)
==5219== by 0x400EEDF: _dl_init (dl-init.c:120)
==5219== by 0x4000ACE: ??? (in /lib/i386-linux-gnu/ld-2.21.so)
Full log file: http://pastebin.com/DQxQtnzK
How do I solve this problem? What should I do?

Answer 1

The leaks are not from your code
Transcribing comments with minimal editing.
Add suppressions; they're 'leaks' caused by the startup code that can't be fixed by you and probably won't be fixed by the developers of the C++ runtime. This is an extensive problem on Mac OS X. There are typically many allocations and a few tens of kilobytes of memory that are allocated by the startup code. (Options include --gen-suppressions=all and --suppressions=suppressions-file.)
This collected the comment:
FATAL: can't open suppressions file "suppressions-file"
Which got the riposte (since I was under time pressure when I made the comment):
Read the manual. You use --gen-suppressions=all to generate the suppressions […]. Then edit the file (there's a placeholder where you're supposed to put an ID/name for each suppression entry). Then you can use the file in subsequent runs with --suppressions=name-you-created. You may need --show-leak-kinds=all, and maybe some others, too (-leak-check=full, for example). Use valgrind --help, but be aware that the output is fairly extensive.
Worked example — Mac OS X 10.11.4
Source (mincpp.cpp)
int main() { return 0; }
Compilation
g++ -O3 -g -std=c++11 mincpp.cpp -o mincpp
(I normally use many more warning options, but with this code, there's really no need.)
Initial run with valgrind
$ valgrind mincpp
==69167== Memcheck, a memory error detector
==69167== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
==69167== Using Valgrind-3.12.0.SVN and LibVEX; rerun with -h for copyright info
==69167== Command: mincpp
==69167==
--69167-- UNKNOWN fcntl 97!
--69167-- UNKNOWN fcntl 97! (repeated 2 times)
--69167-- UNKNOWN fcntl 97! (repeated 4 times)
--69167-- UNKNOWN fcntl 97! (repeated 8 times)
--69167-- UNKNOWN fcntl 97! (repeated 16 times)
--69167-- UNKNOWN fcntl 97! (repeated 32 times)
==69167==
==69167== HEAP SUMMARY:
==69167== in use at exit: 22,195 bytes in 190 blocks
==69167== total heap usage: 255 allocs, 65 frees, 27,947 bytes allocated
==69167==
==69167== LEAK SUMMARY:
==69167== definitely lost: 4,120 bytes in 2 blocks
==69167== indirectly lost: 2,288 bytes in 6 blocks
==69167== possibly lost: 4,880 bytes in 45 blocks
==69167== still reachable: 2,344 bytes in 12 blocks
==69167== suppressed: 8,563 bytes in 125 blocks
==69167== Rerun with --leak-check=full to see details of leaked memory
==69167==
==69167== For counts of detected and suppressed errors, rerun with: -v
==69167== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)
$
That's a lot of leakage for such a minimal program!
The unknown fcntl messages are a nuisance but appear to be 'mostly harmless'; I probably need to rebuild valgrind once more.
Generate suppressions
$ valgrind --gen-suppressions=all --leak-check=full --show-leak-kinds=all mincpp
==69211== Memcheck, a memory error detector
==69211== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
==69211== Using Valgrind-3.12.0.SVN and LibVEX; rerun with -h for copyright info
==69211== Command: mincpp
==69211==
--69211-- UNKNOWN fcntl 97!
--69211-- UNKNOWN fcntl 97! (repeated 2 times)
--69211-- UNKNOWN fcntl 97! (repeated 4 times)
--69211-- UNKNOWN fcntl 97! (repeated 8 times)
--69211-- UNKNOWN fcntl 97! (repeated 16 times)
--69211-- UNKNOWN fcntl 97! (repeated 32 times)
==69211==
==69211== HEAP SUMMARY:
==69211== in use at exit: 22,195 bytes in 190 blocks
==69211== total heap usage: 255 allocs, 65 frees, 27,947 bytes allocated
==69211==
==69211== 24 bytes in 1 blocks are still reachable in loss record 5 of 62
==69211== at 0x1000071FC: malloc_zone_malloc (vg_replace_malloc.c:304)
==69211== by 0x1005DC1E4: _read_images (in /usr/lib/libobjc.A.dylib)
==69211== by 0x1005E19EB: object_setClass (in /usr/lib/libobjc.A.dylib)
==69211== by 0x1005DABC7: gc_init (in /usr/lib/libobjc.A.dylib)
==69211== by 0x1005DA8C1: preopt_init (in /usr/lib/libobjc.A.dylib)
==69211== by 0x1005DA5CA: map_images_nolock (in /usr/lib/libobjc.A.dylib)
==69211== by 0x1005ECC6C: batchFinalizeOnTwoThreads(_malloc_zone_t*, void (*)(auto_zone_cursor*, void (*)(void*, void*), void*), auto_zone_cursor*, unsigned long) (in /usr/lib/libobjc.A.dylib)
==69211== by 0x7FFF5FC047CF: dyld::notifyBatchPartial(dyld_image_states, bool, char const* (*)(dyld_image_states, unsigned int, dyld_image_info const*)) (in /usr/lib/dyld)
==69211== by 0x7FFF5FC04516: dyld::registerImageStateBatchChangeHandler(dyld_image_states, char const* (*)(dyld_image_states, unsigned int, dyld_image_info const*)) (in /usr/lib/dyld)
==69211== by 0x10023789D: dyld_register_image_state_change_handler (in /usr/lib/system/libdyld.dylib)
==69211== by 0x1005D907B: _objc_init (in /usr/lib/libobjc.A.dylib)
==69211== by 0x1001DFC93: _os_object_init (in /usr/lib/system/libdispatch.dylib)
==69211==
{
<insert_a_suppression_name_here>
Memcheck:Leak
match-leak-kinds: reachable
fun:malloc_zone_malloc
fun:_read_images
fun:object_setClass
fun:gc_init
fun:preopt_init
fun:map_images_nolock
fun:_ZL25batchFinalizeOnTwoThreadsP14_malloc_zone_tPFvP16auto_zone_cursorPFvPvS3_ES3_ES2_m
fun:_ZN4dyldL18notifyBatchPartialE17dyld_image_statesbPFPKcS0_jPK15dyld_image_infoE
fun:_ZN4dyld36registerImageStateBatchChangeHandlerE17dyld_image_statesPFPKcS0_jPK15dyld_image_infoE
fun:dyld_register_image_state_change_handler
fun:_objc_init
fun:_os_object_init
}
==69211== 24 bytes in 1 blocks are still reachable in loss record 6 of 62
==69211== at 0x1000071FC: malloc_zone_malloc (vg_replace_malloc.c:304)
==69211== by 0x1005DC1E4: _read_images (in /usr/lib/libobjc.A.dylib)
==69211== by 0x1005E19EB: object_setClass (in /usr/lib/libobjc.A.dylib)
==69211== by 0x1005DCC96: NXHashInsert (in /usr/lib/libobjc.A.dylib)
==69211== by 0x1005DB9B8: _read_images (in /usr/lib/libobjc.A.dylib)
==69211== by 0x1005DA5DA: map_images_nolock (in /usr/lib/libobjc.A.dylib)
==69211== by 0x1005ECC6C: batchFinalizeOnTwoThreads(_malloc_zone_t*, void (*)(auto_zone_cursor*, void (*)(void*, void*), void*), auto_zone_cursor*, unsigned long) (in /usr/lib/libobjc.A.dylib)
==69211== by 0x7FFF5FC047CF: dyld::notifyBatchPartial(dyld_image_states, bool, char const* (*)(dyld_image_states, unsigned int, dyld_image_info const*)) (in /usr/lib/dyld)
==69211== by 0x7FFF5FC04516: dyld::registerImageStateBatchChangeHandler(dyld_image_states, char const* (*)(dyld_image_states, unsigned int, dyld_image_info const*)) (in /usr/lib/dyld)
==69211== by 0x10023789D: dyld_register_image_state_change_handler (in /usr/lib/system/libdyld.dylib)
==69211== by 0x1005D907B: _objc_init (in /usr/lib/libobjc.A.dylib)
==69211== by 0x1001DFC93: _os_object_init (in /usr/lib/system/libdispatch.dylib)
==69211==
{
<insert_a_suppression_name_here>
Memcheck:Leak
match-leak-kinds: reachable
fun:malloc_zone_malloc
fun:_read_images
fun:object_setClass
fun:NXHashInsert
fun:_read_images
fun:map_images_nolock
fun:_ZL25batchFinalizeOnTwoThreadsP14_malloc_zone_tPFvP16auto_zone_cursorPFvPvS3_ES3_ES2_m
fun:_ZN4dyldL18notifyBatchPartialE17dyld_image_statesbPFPKcS0_jPK15dyld_image_infoE
fun:_ZN4dyld36registerImageStateBatchChangeHandlerE17dyld_image_statesPFPKcS0_jPK15dyld_image_infoE
fun:dyld_register_image_state_change_handler
fun:_objc_init
fun:_os_object_init
}
…
==69211== LEAK SUMMARY:
==69211== definitely lost: 4,120 bytes in 2 blocks
==69211== indirectly lost: 2,288 bytes in 6 blocks
==69211== possibly lost: 4,880 bytes in 45 blocks
==69211== still reachable: 2,344 bytes in 12 blocks
==69211== suppressed: 8,563 bytes in 125 blocks
==69211==
==69211== For counts of detected and suppressed errors, rerun with: -v
==69211== ERROR SUMMARY: 6 errors from 6 contexts (suppressed: 12 from 12)
$
Sometimes, I add --num-callers=NN for some number NN, but the default seems to be 12 on my build (it was less in earlier versions, I think), which is adequate.
Generate suppressions in file min.suppressions
$ valgrind --gen-suppressions=all --leak-check=full --show-leak-kinds=all mincpp 2>./min.suppressions
$
Edit min.suppressions
Delete lines starting == and --; what's left are suppressions. Add names for the suppressions. End result is similar to:
{
Mac-OSX-10.11.4-GCC-5.3.0-C++-Suppressions-001
Memcheck:Leak
match-leak-kinds: reachable
fun:malloc_zone_malloc
fun:_read_images
fun:object_setClass
fun:gc_init
fun:preopt_init
fun:map_images_nolock
fun:_ZL25batchFinalizeOnTwoThreadsP14_malloc_zone_tPFvP16auto_zone_cursorPFvPvS3_ES3_ES2_m
fun:_ZN4dyldL18notifyBatchPartialE17dyld_image_statesbPFPKcS0_jPK15dyld_image_infoE
fun:_ZN4dyld36registerImageStateBatchChangeHandlerE17dyld_image_statesPFPKcS0_jPK15dyld_image_infoE
fun:dyld_register_image_state_change_handler
fun:_objc_init
fun:_os_object_init
}
{
Mac-OSX-10.11.4-GCC-5.3.0-C++-Suppressions-002
Memcheck:Leak
match-leak-kinds: reachable
fun:malloc_zone_malloc
fun:_read_images
fun:object_setClass
fun:NXHashInsert
fun:_read_images
fun:map_images_nolock
fun:_ZL25batchFinalizeOnTwoThreadsP14_malloc_zone_tPFvP16auto_zone_cursorPFvPvS3_ES3_ES2_m
fun:_ZN4dyldL18notifyBatchPartialE17dyld_image_statesbPFPKcS0_jPK15dyld_image_infoE
fun:_ZN4dyld36registerImageStateBatchChangeHandlerE17dyld_image_statesPFPKcS0_jPK15dyld_image_infoE
fun:dyld_register_image_state_change_handler
fun:_objc_init
fun:_os_object_init
}
…
{
Mac-OSX-10.11.4-GCC-5.3.0-C++-Suppressions-021
Memcheck:Leak
match-leak-kinds: definite
fun:malloc_zone_memalign
fun:_ZL11addSubclassP10objc_classS0_
fun:_ZL12realizeClassP10objc_class
fun:_ZL12realizeClassP10objc_class
fun:_ZN4dyldL12notifySingleE17dyld_image_statesPK11ImageLoader
fun:_ZN11ImageLoader23recursiveInitializationERKNS_11LinkContextEjRNS_21InitializerTimingListERNS_15UninitedUpwardsE
fun:_ZN11ImageLoader19processInitializersERKNS_11LinkContextEjRNS_21InitializerTimingListERNS_15UninitedUpwardsE
fun:_ZN11ImageLoader19processInitializersERKNS_11LinkContextEjRNS_21InitializerTimingListERNS_15UninitedUpwardsE
fun:_ZN11ImageLoader15runInitializersERKNS_11LinkContextERNS_21InitializerTimingListE
fun:_ZN4dyld24initializeMainExecutableEv
fun:_ZN4dyld5_mainEPK12macho_headermiPPKcS5_S5_Pm
fun:_ZN13dyldbootstrap5startEPK12macho_headeriPPKclS2_Pm
}
Rerun with --suppressions=./min.suppressions
$ valgrind --suppressions=./min.suppressions mincpp
==72028== Memcheck, a memory error detector
==72028== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
==72028== Using Valgrind-3.12.0.SVN and LibVEX; rerun with -h for copyright info
==72028== Command: mincpp
==72028==
--72028-- UNKNOWN fcntl 97!
--72028-- UNKNOWN fcntl 97! (repeated 2 times)
--72028-- UNKNOWN fcntl 97! (repeated 4 times)
--72028-- UNKNOWN fcntl 97! (repeated 8 times)
--72028-- UNKNOWN fcntl 97! (repeated 16 times)
--72028-- UNKNOWN fcntl 97! (repeated 32 times)
==72028==
==72028== HEAP SUMMARY:
==72028== in use at exit: 22,195 bytes in 190 blocks
==72028== total heap usage: 255 allocs, 65 frees, 27,947 bytes allocated
==72028==
==72028== LEAK SUMMARY:
==72028== definitely lost: 0 bytes in 0 blocks
==72028== indirectly lost: 0 bytes in 0 blocks
==72028== possibly lost: 0 bytes in 0 blocks
==72028== still reachable: 0 bytes in 0 blocks
==72028== suppressed: 22,195 bytes in 190 blocks
==72028==
==72028== For counts of detected and suppressed errors, rerun with: -v
==72028== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)
$
This shows that the previously reported errors are now suppressed.