How to explicitly call CRT startup functions

Question

Is there any way I can explicitly in my code call the functions that are normally called in mainCRTStartup functions? I'm specifically interested initterm and initterm_e functions. Even thought my program is linked with crt (it has to be, right?) I couldn't just call initterm - I tried to declare and just invoke and I got undefined reference.

Is there any way to do it?

Answer 1

the _initterm , and _initterm_e (note in msdn _initterm_e is wrong declared - really it used _PIFV type) is exported by different CRT dlls. and it declared in lib files too. and implementation of this functions is very simply:

typedef void (__cdecl *_PVFV)();

void _initterm(const _PVFV *ppfn, const _PVFV *end)
{
    do 
    {
        if (_PVFV pfn = *++ppfn)
        {
            pfn();
        }
    } while (ppfn < end);
}

typedef int  (__cdecl *_PIFV)();

int _initterm_e(const _PIFV *ppfn, const _PIFV *end)
{
    do 
    {
        if (_PIFV pfn = *++ppfn)
        {
            if (int err = pfn()) return err;
        }
    } while (ppfn < end);

    return 0;
}

so you can import it ot use own implementation. here faster question - what is use as input parameters ?

say c++ ( CL compiler how minimum) use ( ".CRT$XCA", ".CRT$XCZ" ) sections for place c++ global initializes. so we can do next:

extern "C"
{
#pragma const_seg(".CRT$XCA")
  const _PVFV __xc_a = 0;
#pragma const_seg(".CRT$XCZ")
  const _PVFV __xc_z = 0;

#pragma const_seg(".CRT$XIA")
  const _PVFV __xi_a = 0;
#pragma const_seg(".CRT$XIZ")
  const _PVFV __xi_z = 0;
}

    /*
     * do initializations
     */
    initret = _initterm_e( &__xi_a, &__xi_z );
    if ( initret != 0 )
        return initret;

    /*
     * do C++ initializations
     */
    _initterm( &__xc_a, &__xc_z );

but here need very good understand - what and why we doing