A Probe function that is injected by profiler may cause unhandled exception in Visual C++

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This article was previously published under Q310827

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SYMPTOMS

If the injection probe function's metadata does not set the miPreserveSig flag through IMetaDataEmit::DefineMethod(), the profiled application might throw unhandled exceptions.

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By default, the DefineMethod() call "mangles" the function signature to do the HRESULT conversion. If the probe function does not return "HRESULT", the resulting mismatch may cause the application that is being profiled to fail.

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RESOLUTION

To avoid this problem, use the miPreserveSig flag when you use IMetaDataEmit::DefineMethod() to inject a probe function. For example:

(pModuleInfo->m_pEmit)->DefineMethod( mdTokenNil,
		   L"ILCoverFunc",
		   mdPublic|mdStatic|mdPinvokeImpl,
		   rgSig,
		   sizeof( rgSig ),
		   0,
		   miIL | miPreserveSig,  // NOTE THE miPreserveSig.
		   &(pModuleInfo->m_tkProbe) )

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