sehsupp.c

C标准库源代码

/***
*sehsupp.c - helper functions for Structured Exception Handling support
*
*       Copyright (C) 1993-1997, Microsoft Corporation. All rights reserved.
*
*Purpose:
*       Contains _rt_probe_read.  Helper for the SEH runtime support
*       routines (longjmp in particular).  Much of the SEH code is written
*       in asm, so these routines are available when probing memory in ways
*       that must be guarded with __try/__except in case of access violation.
*
*******************************************************************************/

#ifndef WIN32_LEAN_AND_MEAN
#define WIN32_LEAN_AND_MEAN 1
#endif  /* WIN32_LEAN_AND_MEAN */

#include <windows.h>

/***
*BOOL __stdcall _rt_probe_read4 - Check if a DWORD is readable
*
*Purpose:
*  Internal support function called by longjmp.  Check if a DWORD is
*  readable under a __try/__except.
*
*Entry:
*  DWORD * p - Pointer to DWORD to be probed
*
*Exit:
*  Success: TRUE - Able to read
*  Failure: FALSE - Access violation while reading
*
******************************************************************************/

BOOL __stdcall _rt_probe_read4(
    DWORD * ptr)
{
    BOOL readable;

    __try
    {
        *(volatile DWORD *)ptr;
        readable = TRUE;
    }
    __except (GetExceptionCode() == EXCEPTION_ACCESS_VIOLATION
                ? EXCEPTION_EXECUTE_HANDLER
                : EXCEPTION_CONTINUE_SEARCH)
    {
        readable = FALSE;
    }

    return readable;
}