I am testing C code for memory leaks and can't seem to find the source of the leaks because there are 0 errors. Valgrind reports that there is a (quite significant) memory leak:
==30492== Memcheck, a memory error detector
==30492== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==30492== Using Valgrind-3.14.0.GIT and LibVEX; rerun with -h for copyright
info
==30492== Command: ./a.out --leak-check=full --track-origins=yes
==30492==
(This is where the input and output cases are displayed, which are a lot)
==30492==
==30492== HEAP SUMMARY:
==30492== in use at exit: 39,155 bytes in 167 blocks
==30492== total heap usage: 380 allocs, 213 frees, 53,426 bytes allocated
==30492==
==30492== LEAK SUMMARY:
==30492== definitely lost: 20,480 bytes in 2 blocks
==30492== indirectly lost: 2,064 bytes in 1 blocks
==30492== possibly lost: 0 bytes in 0 blocks
==30492== still reachable: 348 bytes in 9 blocks
==30492== suppressed: 16,263 bytes in 155 blocks
==30492== Rerun with --leak-check=full to see details of leaked memory
==30492==
==30492== For counts of detected and suppressed errors, rerun with: -v
==30492== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 4 from 4)
The code is written in a few files and consists of hundreds of lines, so posting it here would probably be a bit much. Could anyone explain what could be the problem here? Or would you need to see the actual code to give an answer? I can find only little documentation on valgrind and am quite stuck here.
(valgrind suggests to rerun with --leak-check=full, but that is what I did to get this output)
It is possible to get false positives (e.g. in shared library initializers, or things like libcrypto.so which does leak some allocation).
However, you should always check - most likely you're forgetting some allocation.
In your output, we can see:
Command: ./a.out --leak-check=full --track-origins=yes
This indicates you've invoked valgrind with:
valgrind ./a.out --leak-check=full --track-origins=yes
You should use this:
valgrind --leak-check=full --track-origins=yes ./a.out
If you find a leak (or other diagnostic) that you cannot control because it's internal to a third-party library, you can make a suppression file