References for FFI and calling C from V

[KevinDaSilvaS]

Hey everyone I was trying to use C libraries in my V code, but I didnt manage to make it work on windows using the docs available(probably because I dont know C), someone has access to more detailed documentation on it?

[JalonSolov]

For now, you definitely need to know C to get this to work.

Perhaps in the future, V will get a WinAPI wrapper layer to work with the system, and other wrapper layers for other useful Windows versions of C libraries.

You can try running v translate wrapper on some of those C library files, but if it doesn't work, you won't be able to figure out why, nor be able to write your own wrappers, without knowing C.

[Wajinn]

Agree that the best case will likely be to translate C to V, else the person should be familiar with or studying some C too, to better understand what's possibly going wrong or needs changes.

Depending on what a person is doing on Windows, if using the default TCC, you might need the full winapi.
TCC's full winapi (named as- winapi-full-for-0.9.27.zip) can be found here . Download and extract to somewhere that doesn't include spaces (to avoid issues).

You can then do an alternative run/compile with the below (example).
v -cc tcc -cflags "-isystem path\to\full-winapi\include\winapi" run example.v

In regards to the V documentation, the example does kind of show how it's done, but is not a simple example for someone to start out with. I suppose a bit more or another example could be added to the documentation.

/* 
 * May need to use #flag and/or #include at top, depending on C functions used. 
 * On Windows, may need full winapi for TCC, as header/function found there.
 * https://github.com/vlang/v/blob/master/doc/docs.md#passing-c-compilation-flags
 * https://github.com/vlang/v/blob/master/doc/docs.md#including-c-code
 * Or attemept to translate C to V - https://github.com/vlang/v/blob/master/doc/docs.md#translating-c-to-v
 * Simple example below
*/

fn  C.GetSystemMetrics(nIndex int) int // Declare C functions that are to be used.

fn main() {
	height, width := screen_size()  
	println('${height}') 
	println('${width}')  

}

fn screen_size() (int, int) {
	height := int(C.GetSystemMetrics(C.SM_CYSCREEN))    
	width := int(C.GetSystemMetrics(C.SM_CXSCREEN))  
	return height, width  
}

[terremoth]

Will be nice to have support for FFI and Win32 API, also COM access