Re: backtrace

> > > Can you forward me your Email? My understanding is that if it compiles, > > > it should work. > > > > Well, it works under some conditions, as does Win2000. > > It works if it compiles, sarcasm aside. main(){*(char*)0=1;} compiles as well, but does not work on most platforms. > > 1.: "The object ap may be passed as an argument to another > > function; if that function invokes the va_arg macro > > with parameter ap, the value of ap in the calling > > function is indeterminate and shall be passed to the > > va_end macro prior to any further reference to ap. > > Where are you reading this? It sounds very odd and I assume it would be > wrong (or otherwise useless to do) on every implementation. "7.15 Variable arguments <stdarg.h>," paragraph 3, page 262, ISO/IEC 9899:1999. > > 2.: There are two ways to reinitialize a va_list. Old > > implementations don't support va_copy. va_start cannot > > be used in a function with a fixed number of arguments. > > Essentially, it means that a function that receives a va_list argument, > cannot use it more than once (unless it uses the non portable va_copy()). > Sounds weird to me. Footnote (212) implies that it is permitted to pass a pointer to the object, instead of the object itself, so that the other constraints don't apply. It does not discuss any further semantics of this operation though (which is logical, since conforming implementations will supply va_copy). So, if we should ever need this kind of functionality, the function should be declared as type f(params, va_list *ap); To use ap, we would need to initialize a private copy: va_list f; va_copy(f, *ap); va_arg(f, ..); Since va_copy is not available everywhere, we define it as: #ifndef va_copy #define va_copy(dest, src) memcpy((dest),(src),sizeof(*(src))) #endif This should be safe, unless va_arg modifies anything else beside the va_list it operates on. - Sascha