Sv3sch

As i tried to compile this portion of the Lomoco_Object.c code:


static void * Class_ctor (void * _self, va_list * app)
{
...
va_list ap = * app;
...


on my ppc i stumbled across a compiler error:

error:invalid initializer

which basically tells me *app is not of the type va_list, which struck me as odd on first sight. Some googling and fumbling arround with cc -E made me aware of the fact that the implementation of variable argument lists seem to be highly architecture dependent, and a more architecture portable way of achieving a copy of an argument list is calling the following GNU C extension (thereby trading compiler portability for arch. portability):


va_list ap;
#ifdef __va_copy
__va_copy( ap, *app );
#else
ap = * app;
#endif


All this made me curious enough to have a look at how all this variadic argument stuff is done in assembly by gcc, so i use cc -O0 -S and had a look at whats going on on that level. But i must admit that ppc assembly is quite different from ia32 *g* so i dug up this ibm article:

PowerPC Assembly

and this reference manual explaining ppc assembly:

PowerPC Microprocessor Family: The Programming Environments for 32-Bit Microprocessors

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