Question

How do you get Valgrind to show exactly where an error occured? I compiled my program (on a Windows machine over a Linux terminal via PuTTy) adding the -g debug option.

When I run Valgrind, I get the Leak and Heap summary, and I definitely have lost memory, but I never get information about where it happens (file name, line). Shouldn’t Valgrind be telling me on what line after I allocate memory, it fails to deallocate later?

==15746==
==15746== HEAP SUMMARY:
==15746==     in use at exit: 54 bytes in 6 blocks
==15746==   total heap usage: 295 allocs, 289 frees, 11,029 bytes allocated
==15746==
==15746== LEAK SUMMARY:
==15746==    definitely lost: 12 bytes in 3 blocks
==15746==    indirectly lost: 42 bytes in 3 blocks
==15746==      possibly lost: 0 bytes in 0 blocks
==15746==    still reachable: 0 bytes in 0 blocks
==15746==         suppressed: 0 bytes in 0 blocks
==15746== Rerun with --leak-check=full to see details of leaked memory
==15746==
==15746== For counts of detected and suppressed errors, rerun with: -v
==15746== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 15 from 8)

Answer 1

Try valgrind --leak-check=full

This normally prints more useful information.
Also add the -O0 flag when compiling so your code doesn’t get optimized.