Why is _mainCRTStartup so slow with debugging on, but fast with debugging off?

I'm using 32-bit GLUT on 64-bit Windows 7 with Visual Studio 2010. The project just contains my C++ implementation and header files. No Win32-specific code.

I do a lot of pixel drawing operations. It's instantaneous with the release configuration, but very slow (at least 5 seconds until it draws) with the debug configuration. I noticed it slowed down more when I drew more. So I figured, pro开发者_Python百科file it.

The Visual C++ profiler says 100% (I'm guessing that's rounded up) of the time is spent in _mainCRTStartup. I understand this is the C run time, but what's causing it to run so slowly in the debug configuration? The equivalent C code is equally instantaneous when in both debug and release configurations. Is there anything special with C++ that makes _mainCRTStartup take much longer?

EDIT: Apparently I overlooked one thing: under _mainCRTStartup frame, there is a reference to Unknown frame(s). I assume this is the main() and its children functions. I cannot get it to actually profile the functions I wrote, either in debug or release. Where do I go after this?

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The debugger is probably having trouble finding the .pdb files for the DLLs that you use. First thing to do is to check your symbol server settings. Tools + Options, Debugging, Symbols. Uncheck the Symbol file locations and try again.

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What the "exclusive % samples" in _mainCRTStartup? Inclusive samples are worthless for this routine.

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_mainCRTStartup is the primary function that calls main. So yes, for every program, 100% of the time is spent inside that function- because it calls all other functions.

You're profiling Debug mode? Just why?