c++ - Convert Address to long - variable results in value? -

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can explain behaviour me pls?

static short ndosomething(const char* pcmsg, ...) {   va_list pvargument;   long ltest;   void* pvtest = null;    va_start(pvargument, pcmsg);    pvtest = va_arg(pvargument, void*);   ltest  = (long) pvtest;    va_end(pvargument);   return 0; }

if call function in main this:

int main(int argc, char* argv[])  {    char actest1[20];    ndosomething("testmessage", 1234567l, actest1);     return 0; }

i thought address of pvtest in ltest, in fact contains 1234567 ...

how possible?

your code contains undefined behavior; standard requires type extracted using va_arg correspond type passed (modulo cv-qualifiers, perhaps): passed long, , read void*, compiler correct.

in practice, compilers generate code no type checking. if on machine, long , void* have same size (and machine has linear addressing), end whatever passed long. if sizes of 2 different, machine little endian, , pass small enough value, might end same value well. not @ guaranteed.


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