Memory Allocation Debug Support: Introduction

Collaboration diagram for Memory Allocation Debug Support: Introduction:

Unless –disable-alloc was specified during configuration then the following memory allocation and de-allocation debugging features are provided by libcwd:

1. Checking if a pointer that is passed to a memory de-allocation function is valid; and if this pointer was previously returned by a corresponding allocation function.
2. Finding the start, size, place of allocation in the source code and allocator type of an allocated memory block when given a pointer which points inside of it (see Finding (Information About) Memory Allocations).
3. Providing means to add type info and a description to the Allocated memory Overview (using AllocTag()).
4. Listing an overview of allocated memory to a Debug Object.
5. Boundary checks of allocated blocks, by means of magic numbers (see also –enable-magic (CWDEBUG_MAGIC)).

Unfortunately it is impossible to support feature 3. in C++ without putting hooks in your code:

• After every memory allocation, the returned pointer should be passed to AllocTag(), passing information that needs to be included in the Allocated memory Overview (this is not needed, though allowed, after a call to realloc()).

A missing AllocTag() will only have effect on the Allocated memory Overview, showing <unknown type> instead of the type and a description of the allocated object.