On Thu, Dec 02, 2021 at 11:29:17PM +0000, Chris Katko via Digitalmars-d-learn wrote: [...] > It seems I can (thanks to the amazing work of D community) simply do: > > ```d > extern(C) int sched_yield(void); // #include <sched.h> > ``` > > however, how does the linker know I need <sched.h> and not some local > library, or SDL library, or SDL2.0 library, etc. Shouldn't I be > specifying the library somewhere?
An extern(C) function exists in the global namespace, namely, `sched_yield` will bind at link time to whatever library exports the symbol `sched_yield`. Most linkers (and linker configurations) will generate an error if there are multiple symbols with the same name defined. (The exception is when a symbol is marked as a "weak" symbol, but that's usually not done except for special purposes.) This is why good libraries like SDL always prefixes their API functions with `SDL_`, for example. In order to prevent confusion of SDL functions with a function of the same name from another library. [...] > Side side question: The above line fails to compile as-is because it > has (void) instead of (). > > ``` > source/app.d(226,16): Error: cannot have parameter of type `void` > ``` > > Should that be corrected in the compiler? Shouldn't () and (void) be > interchangeable as long as you're not doing void*? In C, `int func()` means `func` can take any number of arguments. That's why you need to write `int func(void)` to explicitly say there are NO parameters. But in D, `int func()` means `func` takes no arguments. So you never write `int func(void)`. D's `int func()` == C's `int func(void)`. T -- There are four kinds of lies: lies, damn lies, and statistics.
