Report Hook Functions
Note
This article applies to Visual Studio 2015. If you're looking for the latest Visual Studio documentation, see Visual Studio documentation. We recommend upgrading to the latest version of Visual Studio. Download it here
A report hook function, installed using _CrtSetReportHook, is called every time _CrtDbgReport generates a debug report. You can use it, among other things, for filtering reports to focus on specific types of allocations. A report hook function should have a prototype like the following:
int YourReportHook(int nRptType, char *szMsg, int *retVal);
The pointer that you pass to _CrtSetReportHook is of type _CRT_REPORT_HOOK, as defined in CRTDBG.H:
typedef int (__cdecl *_CRT_REPORT_HOOK)(int, char *, int *);
When the run-time library calls your hook function, the nRptType argument contains the category of the report (_CRT_WARN, _CRT_ERROR, or _CRT_ASSERT), szMsg contains a pointer to a fully assembled report message string, and retVal specifies whether _CrtDbgReport should continue normal execution after generating the report or start the debugger. (A retVal value of zero continues execution, a value of 1 starts the debugger.)
If the hook handles the message in question completely, so that no further reporting is required, it should return TRUE. If it returns FALSE, _CrtDbgReport will report the message normally.