$ film42@mbp ~/D/D/S/C/t/a/build (master)>
valgrind --leak-check=full --dsymutil=yes ./avl_tree_tests
==65466== Memcheck, a memory error detector
==65466== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al.
==65466== Using Valgrind-3.11.0.SVN and LibVEX; rerun with -h for copyright info
==65466== Command: ./avl_tree_tests
==65466==
--65466-- run: /usr/bin/dsymutil "./avl_tree_tests"
Running test: Contains Tests
Malloc'd tree
Mallocing data: Hello!
Malloc'd node
Mallocing data: 3
Malloc'd node
Mallocing data: 4
Malloc'd node
Mallocing data: 5
Malloc'd node
Deleting node: 3
Deleting node: 5
Deleting node: Hello!
Deleting node: 4
Free'd tree
ALL TESTS PASSED
Tests run: 1
==65466==
==65466== HEAP SUMMARY:
==65466==     in use at exit: 38,716 bytes in 423 blocks
==65466==   total heap usage: 516 allocs, 93 frees, 45,137 bytes allocated
==65466==
==65466== 32 bytes in 1 blocks are definitely lost in loss record 29 of 82
==65466==    at 0x1000083B1: malloc (vg_replace_malloc.c:303)
==65466==    by 0x100001D94: avl_node_init (avl_tree.c:16)
==65466==    by 0x100001552: insert_recur (avl_tree.c:125)
==65466==    by 0x1000015B8: insert_recur (avl_tree.c:134)
==65466==    by 0x10000159A: insert_recur (avl_tree.c:132)
==65466==    by 0x1000014B1: avl_insert (avl_tree.c:153)
==65466==    by 0x1000011A0: avl_contains_tests (main.c:45)
==65466==    by 0x1000010D8: avl_all_tests (main.c:83)
==65466==    by 0x10000104A: main (main.c:91)
==65466==
==65466== LEAK SUMMARY:
==65466==    definitely lost: 32 bytes in 1 blocks
==65466==    indirectly lost: 0 bytes in 0 blocks
==65466==      possibly lost: 0 bytes in 0 blocks
==65466==    still reachable: 4,096 bytes in 1 blocks
==65466==         suppressed: 34,588 bytes in 421 blocks
==65466== Reachable blocks (those to which a pointer was found) are not shown.
==65466== To see them, rerun with: --leak-check=full --show-leak-kinds=all
==65466==
==65466== For counts of detected and suppressed errors, rerun with: -v
==65466== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 17 from 17)