As another poster pointed out, if I run this via valgrind (after fixing the first error): > valgrind ./a.out ==4871== Invalid write of size 4 ==4871==

As another poster pointed out, if I run this via valgrind (after fixing the first error): > valgrind ./a.out ==4871== Invalid write of size 4 ==4871== at 0x40073A: vec_push (test.c:40) ==4871== Invalid write of size 4 ==4871== at 0x40073A: vec_push (test.c:40) ==4871== Invalid read of size 4 ==4871== at 0x4007CD: main (test.c:55) ==4871== Invalid read of size 8 ==4871== at 0x400769: vec_free (test.c:46) ==4871== Invalid free() / delete / delete[] / realloc() ==4871== at 0x4C2BDEC: free (...) ==4871== by 0x400770: vec_free (test.c:46)