Invalid write of size 4
   at 0x........: main (custom_alloc.c:79)
 Address 0x........ is 0 bytes after a block of size 40 alloc'd
   at 0x........: custom_alloc (custom_alloc.c:47)
   by 0x........: main (custom_alloc.c:76)

Invalid free() / delete / delete[]
   at 0x........: custom_free (custom_alloc.c:54)
   by 0x........: main (custom_alloc.c:83)
 Address 0x........ is not stack'd, malloc'd or (recently) free'd

Mismatched free() / delete / delete []
   at 0x........: custom_free (custom_alloc.c:54)
   by 0x........: main (custom_alloc.c:86)
 Address 0x........ is 0 bytes inside a block of size 40 alloc'd
   at 0x........: malloc (vg_replace_malloc.c:...)
   by 0x........: main (custom_alloc.c:85)

Invalid read of size 4
   at 0x........: main (custom_alloc.c:89)
 Address 0x........ is not stack'd, malloc'd or (recently) free'd