As indicated above, the malloc library provides a minimal level of checking by default. This includes a check of the integrity of the allocation chain at the point of the local heap buffer on every allocation request. In addition, the flags and CRC of the header are checked for integrity. When the library can locate the neighboring heap buffers, it also checks their integrity. There are also checks specific to each type of allocation request that are done. Call-specific checks are described according to the type of call below.
You can enable additional checks by using the mallopt() call. For more information on the types of checking, and the sources of heap corruption that can be detected, see of "Controlling the level of checking," below.