C valgrind still reachable memory leak but no heap used?

Question

I am working with some original code that reads directly from disk files. There is only one malloc call in the entire beginning code (and I checked that that is no the issue). In my own code, I do not use malloc, strdup, or any other heap calls. However, running valgrind with a full leak check I still get (below).

I don't recognize any of the files that it is showing. I am running this on a Mac OSX with Lion. Is it possible that this is a problem with the system libraries or is their another way to troubleshoot this. I know that some will argue that having reachable memory is okay, but I am curious to know why any of the memory is reachable still.

-

-90966-- REDIR: 0x3a46c7 (free) redirected to 0x55b8 (free)
==90966== 
==90966== HEAP SUMMARY:
==90966==     in use at exit: 6,383 bytes in 33 blocks
==90966==   total heap usage: 34 allocs, 1 frees, 6,899 bytes allocated
==90966== 
==90966== Searching for pointers to 33 not-freed blocks
==90966== Checked 684,888 bytes
==90966== 
==90966== 8 bytes in 1 blocks are still reachable in loss record 1 of 9
==90966==    at 0x5237: malloc (in /usr/local/Cellar/valgrind/3.8.1/lib/valgrind/vgpreload_memcheck-amd64-darwin.so)
==90966==    by 0x7FFF5FC11C2A: malloc (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC19C4E: operator new(unsigned long) (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC0817E: std::vector<char const* (*)(dyld_image_states, unsigned int, dyld_image_info const*), std::allocator<char const* (*)(dyld_image_states, unsigned int, dyld_image_info const*)> >::_M_insert_aux(__gnu_cxx::__normal_iterator<char const* (**)(dyld_image_states, unsigned int, dyld_image_info const*), std::vector<char const* (*)(dyld_image_states, unsigned int, dyld_image_info const*), std::allocator<char const* (*)(dyld_image_states, unsigned int, dyld_image_info const*)> > >, char const* (* const&)(dyld_image_states, unsigned int, dyld_image_info const*)) (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC08260: std::vector<char const* (*)(dyld_image_states, unsigned int, dyld_image_info const*), std::allocator<char const* (*)(dyld_image_states, unsigned int, dyld_image_info const*)> >::insert(__gnu_cxx::__normal_iterator<char const* (**)(dyld_image_states, unsigned int, dyld_image_info const*), std::vector<char const* (*)(dyld_image_states, unsigned int, dyld_image_info const*), std::allocator<char const* (*)(dyld_image_states, unsigned int, dyld_image_info const*)> > >, char const* (* const&)(dyld_image_states, unsigned int, dyld_image_info const*)) (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC054FA: dyld::registerImageStateBatchChangeHandler(dyld_image_states, char const* (*)(dyld_image_states, unsigned int, dyld_image_info const*)) (in /usr/lib/dyld)
==90966==    by 0x2C1ACB: dyld_register_image_state_change_handler (in /usr/lib/system/libdyld.dylib)
==90966==    by 0x2C2ACB: _dyld_initializer (in /usr/lib/system/libdyld.dylib)
==90966==    by 0x1CFE73: libSystem_initializer (in /usr/lib/libSystem.B.dylib)
==90966==    by 0x7FFF5FC0FDA5: ImageLoaderMachO::doModInitFunctions(ImageLoader::LinkContext const&) (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC0FAF1: ImageLoaderMachO::doInitialization(ImageLoader::LinkContext const&) (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC0D2E3: ImageLoader::recursiveInitialization(ImageLoader::LinkContext const&, unsigned int, ImageLoader::InitializerTimingList&) (in /usr/lib/dyld)
==90966== 
==90966== 87 bytes in 7 blocks are still reachable in loss record 2 of 9
==90966==    at 0x5237: malloc (in /usr/local/Cellar/valgrind/3.8.1/lib/valgrind/vgpreload_memcheck-amd64-darwin.so)
==90966==    by 0x342358: strdup (in /usr/lib/system/libsystem_c.dylib)
==90966==    by 0x4E7802: _xpc_strdup (in /usr/lib/system/libxpc.dylib)
==90966==    by 0x4EDCCF: _xpc_dictionary_insert (in /usr/lib/system/libxpc.dylib)
==90966==    by 0x4EDE0E: xpc_dictionary_set_string (in /usr/lib/system/libxpc.dylib)
==90966==    by 0x4EFE8C: _libxpc_initializer (in /usr/lib/system/libxpc.dylib)
==90966==    by 0x1CFE7D: libSystem_initializer (in /usr/lib/libSystem.B.dylib)
==90966==    by 0x7FFF5FC0FDA5: ImageLoaderMachO::doModInitFunctions(ImageLoader::LinkContext const&) (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC0FAF1: ImageLoaderMachO::doInitialization(ImageLoader::LinkContext const&) (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC0D2E3: ImageLoader::recursiveInitialization(ImageLoader::LinkContext const&, unsigned int, ImageLoader::InitializerTimingList&) (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC0D27C: ImageLoader::recursiveInitialization(ImageLoader::LinkContext const&, unsigned int, ImageLoader::InitializerTimingList&) (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC0E0B6: ImageLoader::runInitializers(ImageLoader::LinkContext const&, ImageLoader::InitializerTimingList&) (in /usr/lib/dyld)
==90966== 
==90966== 88 bytes in 1 blocks are still reachable in loss record 3 of 9
==90966==    at 0x5237: malloc (in /usr/local/Cellar/valgrind/3.8.1/lib/valgrind/vgpreload_memcheck-amd64-darwin.so)
==90966==    by 0x2CA9B0: get_or_create_key_element (in /usr/lib/system/libkeymgr.dylib)
==90966==    by 0x2CABC9: _keymgr_get_and_lock_processwide_ptr_2 (in /usr/lib/system/libkeymgr.dylib)
==90966==    by 0x2CAC36: __keymgr_initializer (in /usr/lib/system/libkeymgr.dylib)
==90966==    by 0x1CFE6E: libSystem_initializer (in /usr/lib/libSystem.B.dylib)
==90966==    by 0x7FFF5FC0FDA5: ImageLoaderMachO::doModInitFunctions(ImageLoader::LinkContext const&) (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC0FAF1: ImageLoaderMachO::doInitialization(ImageLoader::LinkContext const&) (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC0D2E3: ImageLoader::recursiveInitialization(ImageLoader::LinkContext const&, unsigned int, ImageLoader::InitializerTimingList&) (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC0D27C: ImageLoader::recursiveInitialization(ImageLoader::LinkContext const&, unsigned int, ImageLoader::InitializerTimingList&) (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC0E0B6: ImageLoader::runInitializers(ImageLoader::LinkContext const&, ImageLoader::InitializerTimingList&) (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC034B7: dyld::initializeMainExecutable() (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC0760A: dyld::_main(macho_header const*, unsigned long, int, char const**, char const**, char const**) (in /usr/lib/dyld)
==90966== 
==90966== 136 bytes in 1 blocks are still reachable in loss record 4 of 9
==90966==    at 0x58DE: calloc (in /usr/local/Cellar/valgrind/3.8.1/lib/valgrind/vgpreload_memcheck-amd64-darwin.so)
==90966==    by 0x4E78FA: _xpc_calloc (in /usr/lib/system/libxpc.dylib)
==90966==    by 0x4E81D4: _xpc_base_create (in /usr/lib/system/libxpc.dylib)
==90966==    by 0x4F1C32: _xpc_domain_create (in /usr/lib/system/libxpc.dylib)
==90966==    by 0x4EFF1E: _libxpc_initializer (in /usr/lib/system/libxpc.dylib)
==90966==    by 0x1CFE7D: libSystem_initializer (in /usr/lib/libSystem.B.dylib)
==90966==    by 0x7FFF5FC0FDA5: ImageLoaderMachO::doModInitFunctions(ImageLoader::LinkContext const&) (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC0FAF1: ImageLoaderMachO::doInitialization(ImageLoader::LinkContext const&) (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC0D2E3: ImageLoader::recursiveInitialization(ImageLoader::LinkContext const&, unsigned int, ImageLoader::InitializerTimingList&) (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC0D27C: ImageLoader::recursiveInitialization(ImageLoader::LinkContext const&, unsigned int, ImageLoader::InitializerTimingList&) (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC0E0B6: ImageLoader::runInitializers(ImageLoader::LinkContext const&, ImageLoader::InitializerTimingList&) (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC034B7: dyld::initializeMainExecutable() (in /usr/lib/dyld)
==90966== 
==90966== 224 bytes in 7 blocks are still reachable in loss record 5 of 9
==90966==    at 0x5237: malloc (in /usr/local/Cellar/valgrind/3.8.1/lib/valgrind/vgpreload_memcheck-amd64-darwin.so)
==90966==    by 0x4E793D: _xpc_malloc (in /usr/lib/system/libxpc.dylib)
==90966==    by 0x4EDCB4: _xpc_dictionary_insert (in /usr/lib/system/libxpc.dylib)
==90966==    by 0x4EDE0E: xpc_dictionary_set_string (in /usr/lib/system/libxpc.dylib)
==90966==    by 0x4EFE8C: _libxpc_initializer (in /usr/lib/system/libxpc.dylib)
==90966==    by 0x1CFE7D: libSystem_initializer (in /usr/lib/libSystem.B.dylib)
==90966==    by 0x7FFF5FC0FDA5: ImageLoaderMachO::doModInitFunctions(ImageLoader::LinkContext const&) (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC0FAF1: ImageLoaderMachO::doInitialization(ImageLoader::LinkContext const&) (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC0D2E3: ImageLoader::recursiveInitialization(ImageLoader::LinkContext const&, unsigned int, ImageLoader::InitializerTimingList&) (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC0D27C: ImageLoader::recursiveInitialization(ImageLoader::LinkContext const&, unsigned int, ImageLoader::InitializerTimingList&) (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC0E0B6: ImageLoader::runInitializers(ImageLoader::LinkContext const&, ImageLoader::InitializerTimingList&) (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC034B7: dyld::initializeMainExecutable() (in /usr/lib/dyld)
==90966== 
==90966== 520 bytes in 7 blocks are still reachable in loss record 6 of 9
==90966==    at 0x5237: malloc (in /usr/local/Cellar/valgrind/3.8.1/lib/valgrind/vgpreload_memcheck-amd64-darwin.so)
==90966==    by 0x342358: strdup (in /usr/lib/system/libsystem_c.dylib)
==90966==    by 0x4E7802: _xpc_strdup (in /usr/lib/system/libxpc.dylib)
==90966==    by 0x4EEBF5: xpc_string_create (in /usr/lib/system/libxpc.dylib)
==90966==    by 0x4EDDFD: xpc_dictionary_set_string (in /usr/lib/system/libxpc.dylib)
==90966==    by 0x4EFE8C: _libxpc_initializer (in /usr/lib/system/libxpc.dylib)
==90966==    by 0x1CFE7D: libSystem_initializer (in /usr/lib/libSystem.B.dylib)
==90966==    by 0x7FFF5FC0FDA5: ImageLoaderMachO::doModInitFunctions(ImageLoader::LinkContext const&) (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC0FAF1: ImageLoaderMachO::doInitialization(ImageLoader::LinkContext const&) (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC0D2E3: ImageLoader::recursiveInitialization(ImageLoader::LinkContext const&, unsigned int, ImageLoader::InitializerTimingList&) (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC0D27C: ImageLoader::recursiveInitialization(ImageLoader::LinkContext const&, unsigned int, ImageLoader::InitializerTimingList&) (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC0E0B6: ImageLoader::runInitializers(ImageLoader::LinkContext const&, ImageLoader::InitializerTimingList&) (in /usr/lib/dyld)
==90966== 
==90966== 608 bytes in 1 blocks are still reachable in loss record 7 of 9
==90966==    at 0x58DE: calloc (in /usr/local/Cellar/valgrind/3.8.1/lib/valgrind/vgpreload_memcheck-amd64-darwin.so)
==90966==    by 0x4E78FA: _xpc_calloc (in /usr/lib/system/libxpc.dylib)
==90966==    by 0x4E81D4: _xpc_base_create (in /usr/lib/system/libxpc.dylib)
==90966==    by 0x4EDFDA: xpc_dictionary_create (in /usr/lib/system/libxpc.dylib)
==90966==    by 0x4EFE63: _libxpc_initializer (in /usr/lib/system/libxpc.dylib)
==90966==    by 0x1CFE7D: libSystem_initializer (in /usr/lib/libSystem.B.dylib)
==90966==    by 0x7FFF5FC0FDA5: ImageLoaderMachO::doModInitFunctions(ImageLoader::LinkContext const&) (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC0FAF1: ImageLoaderMachO::doInitialization(ImageLoader::LinkContext const&) (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC0D2E3: ImageLoader::recursiveInitialization(ImageLoader::LinkContext const&, unsigned int, ImageLoader::InitializerTimingList&) (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC0D27C: ImageLoader::recursiveInitialization(ImageLoader::LinkContext const&, unsigned int, ImageLoader::InitializerTimingList&) (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC0E0B6: ImageLoader::runInitializers(ImageLoader::LinkContext const&, ImageLoader::InitializerTimingList&) (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC034B7: dyld::initializeMainExecutable() (in /usr/lib/dyld)
==90966== 
==90966== 616 bytes in 7 blocks are still reachable in loss record 8 of 9
==90966==    at 0x58DE: calloc (in /usr/local/Cellar/valgrind/3.8.1/lib/valgrind/vgpreload_memcheck-amd64-darwin.so)
==90966==    by 0x4E78FA: _xpc_calloc (in /usr/lib/system/libxpc.dylib)
==90966==    by 0x4E81D4: _xpc_base_create (in /usr/lib/system/libxpc.dylib)
==90966==    by 0x4EEBEA: xpc_string_create (in /usr/lib/system/libxpc.dylib)
==90966==    by 0x4EDDFD: xpc_dictionary_set_string (in /usr/lib/system/libxpc.dylib)
==90966==    by 0x4EFE8C: _libxpc_initializer (in /usr/lib/system/libxpc.dylib)
==90966==    by 0x1CFE7D: libSystem_initializer (in /usr/lib/libSystem.B.dylib)
==90966==    by 0x7FFF5FC0FDA5: ImageLoaderMachO::doModInitFunctions(ImageLoader::LinkContext const&) (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC0FAF1: ImageLoaderMachO::doInitialization(ImageLoader::LinkContext const&) (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC0D2E3: ImageLoader::recursiveInitialization(ImageLoader::LinkContext const&, unsigned int, ImageLoader::InitializerTimingList&) (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC0D27C: ImageLoader::recursiveInitialization(ImageLoader::LinkContext const&, unsigned int, ImageLoader::InitializerTimingList&) (in /usr/lib/dyld)
==90966==    by 0x7FFF5FC0E0B6: ImageLoader::runInitializers(ImageLoader::LinkContext const&, ImageLoader::InitializerTimingList&) (in /usr/lib/dyld)
==90966== 
==90966== 4,096 bytes in 1 blocks are still reachable in loss record 9 of 9
==90966==    at 0x5237: malloc (in /usr/local/Cellar/valgrind/3.8.1/lib/valgrind/vgpreload_memcheck-amd64-darwin.so)
==90966==    by 0x34F3F7: __smakebuf (in /usr/lib/system/libsystem_c.dylib)
==90966==    by 0x345D19: __swsetup (in /usr/lib/system/libsystem_c.dylib)
==90966==    by 0x3466C3: __vfprintf (in /usr/lib/system/libsystem_c.dylib)
==90966==    by 0x34618D: vfprintf_l (in /usr/lib/system/libsystem_c.dylib)
==90966==    by 0x34F2CF: printf (in /usr/lib/system/libsystem_c.dylib)
==90966==    by 0x1000014D0: main (in .//diskimageaccess)
==90966== 
==90966== LEAK SUMMARY:
==90966==    definitely lost: 0 bytes in 0 blocks
==90966==    indirectly lost: 0 bytes in 0 blocks
==90966==      possibly lost: 0 bytes in 0 blocks
==90966==    still reachable: 6,383 bytes in 33 blocks
==90966==         suppressed: 0 bytes in 0 blocks
==90966== 
==90966== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)
==90966== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

EDIT:

I tried moving the code over to a Linux machine and it compiles and runs perfectly cleanly without any memory errors. Any ideas why this is?

Answer 1

The reachable memory messages are not a real problem, but can be a nuisance because they can drown out the real problems (scrolling blindness). The memory gets allocated by OS X XPC. Perhaps you are talking to an OS X service in your program.

For my own development I use a cleanup-function shut_up_valgrind(). This deallocates everything just before exit. I know this is superfluous, because the operating system will free all the memory used by the process. But in my experience it forced me to write more robust code because I had to think about the memory and discovered many well hidden memory allocation mistakes.

Now, if you have dependencies like on XPC, you can look for cleanup-functions. Try to find out. Perhaps it suffices to close something. Then call the cleanup-functions just before exit from your shut_up_valgrind() function.

Answer 2

No need to worry about still reachable memory.

You can see clearly from call stack in valgrind logfile that memory is being allocated from heap via memory functions. viz malloc() & calloc()

Answer 3

Well, someone must be using these functions if valgrind tells you that. If you're sure that you are not using any heap-functions then some of your dependencies is using malloc/calloc. Which libraries do you use?