On OSX Valgrind reports this memory leak, Where is it coming from?

Question

On OSX Valgrind reports this memory leak, Where is it coming from? The code is c compiled with g++ as c++ code (i do this for function overloading).

==13088== 18 bytes in 1 blocks are definitely lost in loss record 82 of 264
==13088==    at 0x1F25DC: malloc_zone_malloc (vg_replace_malloc.c:267)
==13088==    by 0xA1AEDA: malloc_set_zone_name (in /usr/lib/system/libsystem_c.dylib)
==13088==    by 0xA1B4A7: _malloc_initialize (in /usr/lib/system/libsystem_c.dylib)
==13088==    by 0xA1B5DD: malloc_good_size (in /usr/lib/system/libsystem_c.dylib)
==13088==    by 0x4EFA6E: __CFStringChangeSizeMultiple (in /System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation)
==13088==    by 0x4F3900: CFStringAppend (in /System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation)
==13088==    by 0x506F91: _convertToURLRepresentation (in /System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation)
==13088==    by 0x60F963: _CFURLInit (in /System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation)
==13088==    by 0x4FF268: CFURLCreateWithFileSystemPathRelativeToBase (in /System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation)
==13088==    by 0x4FF8EE: CFURLCreateWithFileSystemPath (in /System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation)
==13088==    by 0x515735: _CFBundleGetMainBundleAlreadyLocked (in /System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation)
==13088==    by 0x515663: CFBundleGetMainBundle (in /System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation)
==13088==    by 0x539533: cacheBundleInfo (in /System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation)
==13088==    by 0x5394B3: _CFAppVersionCheckLessThan (in /System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation)
==13088==    by 0x56C35B: __CFInitialize (in /System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation)
==13088==    by 0x8FE11243: ImageLoaderMachO::doImageInit(ImageLoader::LinkContext const&) (in /usr/lib/dyld)
==13088==    by 0x8FE10CB3: ImageLoaderMachO::doInitialization(ImageLoader::LinkContext const&) (in /usr/lib/dyld)
==13088==    by 0x8FE0E21F: ImageLoader::recursiveInitialization(ImageLoader::LinkContext const&, unsigned int, ImageLoader::InitializerTimingList&) (in /usr/lib/dyld)
==13088==    by 0x8FE0E1B5: ImageLoader::recursiveInitialization(ImageLoader::LinkContext const&, unsigned int, ImageLoader::InitializerTimingList&) (in /usr/lib/dyld)
==13088==    by 0x8FE0F1BF: ImageLoader::runInitializers(ImageLoader::LinkContext const&, ImageLoader::InitializerTimingList&) (in /usr/lib/dyld)
==13088==    by 0x8FE03655: dyld::initializeMainExecutable() (in /usr/lib/dyld)
==13088==    by 0x8FE07EF1: dyld::_main(macho_header const*, unsigned long, int, char const**, char const**, char const**) (in /usr/lib/dyld)
==13088==    by 0x8FE012EE: dyldbootstrap::start(macho_header const*, int, char const**, long, macho_header const*) (in /usr/lib/dyld)
==13088==    by 0x8FE01062: _dyld_start (in /usr/lib/dyld)
==13088==    by 0xFFF: ???

EDIT: also, how would I release this memory?

Answer 1

The allocation is completely out of your control; the free is likewise substantially impossible for you. This should be added to the list of known, detected, recorded but ignored items ('suppressed' is the jargon).

When I run a program under valgrind 3.7.0 on MacOS X 10.7.2, I get a summary like:

==71989== 
==71989== HEAP SUMMARY:
==71989==     in use at exit: 6,191 bytes in 33 blocks
==71989==   total heap usage: 33 allocs, 0 frees, 6,191 bytes allocated
==71989== 
==71989== LEAK SUMMARY:
==71989==    definitely lost: 0 bytes in 0 blocks
==71989==    indirectly lost: 0 bytes in 0 blocks
==71989==      possibly lost: 0 bytes in 0 blocks
==71989==    still reachable: 6,191 bytes in 33 blocks
==71989==         suppressed: 0 bytes in 0 blocks
==71989== Rerun with --leak-check=full to see details of leaked memory
==71989== 
==71989== For counts of detected and suppressed errors, rerun with: -v
==71989== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 1 from 1)

This is from a program that does no explicit memory allocation - printf() may trigger some allocation, but most of those bytes are allocated in system libraries. You've clearly got a deeper than normal value set for the traceback (--num-callers=N).

Look in the manual for how to add a suppression record properly, but valgrind --help offers:

--num-callers=<number>    show <number> callers in stack traces [12]
--error-limit=no|yes      stop showing new errors if too many? [yes]
--error-exitcode=<number> exit code to return if errors found [0=disable]
--show-below-main=no|yes  continue stack traces below main() [no]
--suppressions=<filename> suppress errors described in <filename>
--gen-suppressions=no|yes|all    print suppressions for errors? [no]

So, you could get valgrind to generate the suppression string for you to add to a file which you then use in subsequent runs.

Extra options read from ~/.valgrindrc, $VALGRIND_OPTS, ./.valgrindrc