Q33366: How _fheapwalk() Checks the Heap

Article: Q33366
Product(s): See article
Version(s): 5.00 5.10 | 5.10
Operating System(s): MS-DOS | OS/2
Keyword(s): ENDUSER | | mspl13_c
Last Modified: 27-JUL-1988

The following information describes how _fheapwalk() checks the
heap.

   The _fheapwalk() function traverses those parts of the far heap
that have been allocated either by fmalloc() or by a system call. This
process is done by covering one such allocation per call of
_fheapwalk(), independent of the size of the block allocated.
   On each call of _fheapwalk(), a manifest-constant int is returned
as documented on Page 357 of the "Microsoft C 5.1 Optimizing Compiler
Run-Time Reference Library" manual.
   Also, a pointer to a structure is returned that contains
information about the block allocated, which also is documented on
Page 356 of the C manual.
   One undocumented feature of the function is that it does not return
the actual memory address of an _fmalloc()ed block, only the block's
size.
   As a result, it is incorrect to assume that the memory location of
the beginning of a block can be determined by adding up the values of
the blocks already allocated. The header information in each such
block is omitted from the structure whose pointer is returned by
_fmalloc(). In particular, the size of the header is omitted from the
structure.

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