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Note Microsoft Visual C++ 2005, Microsoft Visual C++ .NET 2003, and Microsoft Visual C++ .NET 2002 support both the managed code model that is provided by the Microsoft .NET Framework and the unmanaged native Microsoft Windows code model. The information in this article applies only to unmanaged Visual C++ code.
The PageHeap utility can be enabled for applications so that all malloc, new, and heapAlloc allocations are monitored automatically for memory errors. This article contains the PageHeap utility, plus a PageHeap1 sample that demonstrates how to use the utility to detect memory errors.
PageHeap1 is a Microsoft Visual C++ project with several types of memory errors. To enable PageHeap on this sample application, type in the following from the command line:
pageheap /enable pgh.exe 0x01Then, type in the following, and note the application name that PageHeap monitors:
pageheapFor many applications, 0x01 is the only flag you need. You can get more information on its usage by running PageHeap with the question mark flag (/?) from the command line. Windows XP comes with a tool called Application Verifier which ships with the Application Compatibility Toolkit. This tool can be used instead of PageHeap. The Application Verifier can be installed from the Support folder on the Windows XP CD-ROM and is called Act20.exe.
PageHeap returns a pointer to allocated memory on 8 byte boundaries. The end of the returned pointer is followed by 0 to 7 guard bytes (depending on the size requested, 0 to 7 bytes are added to round up the request size to be on an 8 byte boundry), followed by a memory page marked PAGE_NOACCESS (see VirtualAlloc documentation for more information). For example:
PageHeap returns a pointer to the 5 bytes plus 3 guard bytes to make up a total of 8 bytes, such as .....XXX . If the memory allocation size is a multiple of eight, there are no guard bytes added to the returned pointer.
If the end of the allocation is overwritten, the guard bytes change and PageHeap causes an Access Violation (AV) when the memory is freed. If the application reads or writes past the allocation (including the guard bytes), it incurs an instant AV.
How to use PageHeap1 sample
Visual C++ .NET
Release Date: June 25, 2002
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Article ID: 264471 - Last Review: September 20, 2012 - Revision: 7.0
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