_heapchk() Performs Consistency Check on Heap

MS-DOS                      | OS/2            | WINDOWS

The information in this article applies to:

• The C Run-time (CRT), included with:

      - Microsoft C for MS-DOS, versions 5.1, 6.0, 6.0a, and 6.0ax
      - Microsoft C for OS/2, versions 5.1, 6.0, and 6.0a
      - Microsoft C/C++ for MS-DOS, version 7.0
      - Microsoft Visual C++ for Windows, versions 1.0 and 1.5
  

SUMMARY

The _heapchk() routine performs a consistency check on the heap by examining the header information of the memory blocks in the heap; it cannot, however, detect corruption of data within the heap's nodes. The _heapchk routine can only detect corruption of the heap's header information.

The _heapchk() routine checks for the following:

• It checks to see if any heap has been allocated. If not, _heapchk() returns _HEAPEMPTY.
• It checks the beginning of the heap block to see if the first allocation block has been corrupted; if so, it returns _HEAPBADBEGIN. (Note that only the header information is checked.)
• It scans through the far heap block, moving from node to node. For each node, it checks the header information to make sure it has not been corrupted; if so, _heapchk() returns _HEAPBADNODE. Note that the only kind of corruption _heapchk() can detect is an out-of- bounds value in the header; it cannot detect corrupted data within the heap block itself. If the fill value passed is not _HEAPSET_NOFILL, and the block is unallocated, _heapchk() fills memory with the fill value.
• If _heapchk() makes it all the way through the heap (that is, it checks the headers for all nodes), it returns _HEAPOK.

MORE INFORMATION

Microsoft C versions 6.0 and later also provide the _heapwalk() functions, which can aid in debugging memory allocation problems. More information on the _heapwalk() function may be found in the online help provided with Microsoft C version 6.0 and later.