可变参数列表打印垃圾

Question

Following function prints garbage on console. Cannot understand the issue. Below is a test code fragment.

void
format(
    const char* pcszFormat,
    ...
    )
{
    va_list VarArglist;

    va_start(VarArglist, pcszFormat);
    printf(pcszFormat, VarArglist);
    va_end(VarArglist);
}


int wmain(int argc, wchar_t *argv[])
{
    string strTest;
    const char *pcszFormatted;

    format("%x %S", 10, "Test");

    //printf("\nFormatted string: %s", pcszFormatted);
    getchar();
    return 0;
}

Answer 1

You invoked undefined behavior by passing data having wrong type to printf() . You should use vprintf() to work with va_list .

Also don't forget to change %S to %s in order to work with normal string or change "Test" to L"Test" in order to work with wide string, or you will invoke undefined behavior by passing data having wrong type to printf() family again.

Answer 2

You can't pass va_list to printf . Use vprintf instead.