C Exception handling

Question

I would like to know how to handle exceptions in C, specifically EXCEPTION_GUARD_PAGE exceptions.

I will try explaining the situation more briefly:

I would like to mark a section/pages section as PAGE_GUARD, and whenever the program hits them I would like to perform a few tasks, I tried causing the exception with a classical VirtualAlloc -> Write -> Exception hit but I do know to catch the exception in C

I'd appreciate the help. Thanks in advance.

Answer 1

MSDN has everything you need:

• Using an Exception Handler
• The try-except Statement

In this particular case you want something in this vein:

__try
{
  /* Code that may cause exceptions... */
}
__except(GetExceptionCode() == EXCEPTION_GUARD_PAGE 
      ? EXCEPTION_EXECUTE_HANDLER
      : EXCEPTION_CONTINUE_SEARCH)
{
  /* Exception handling code... */
}

EDIT (in response to OP's comment):

The above code would do (MSDN is helpful again), but in this case there's more portable (no dependency on MSVC's extensions) and arguably less ugly solution: register a top-level exception filter using SetUnhandledExceptionFilter and let it handle the situation:

/* Our top-level exception filter. */
LONG WINAPI MyUnhandledExceptionFilter(EXCEPTION_POINTERS* exceptionInfo)
{
  DWORD exceptionCode = exceptionInfo->ExceptionRecord->ExceptionCode;
  if(exceptionCode == EXCEPTION_GUARD_PAGE)
  {
    /* Handle the situation somehow... */
    /* ...and resume the exception from the place the exception was thrown. */
    return EXCEPTION_CONTINUE_EXECUTION;
  }
  else
  {
    /* Unknown exception, let another exception filter worry about it. */
    return EXCEPTION_CONTINUE_SEARCH;
  }
}

/* Somewhere else in the code: */
SetUnhandledExceptionFilter(&MyUnhandledExceptionFilter);