Linking C libraries with DMD

[jmh530 via Digitalmars-d-learn]

On Friday, 22 January 2016 at 01:34:00 UTC, bachmeier wrote:
>
> Have you used pragma(lib)? 
> https://dlang.org/spec/pragma.html#lib
>  There's also a section on it in Learning D.
>

Looks like the sections are split apart by a couple hundred 
pages. I tried it with the .lib I created earlier without much 
luck. Also note that the LearningD section recommends not using 
the pragma. At this point, I'd rather just having something 
working.

> I don't use Windows much, but when I link to a dll, that's what 
> I do. I've actually never used -L options on Windows. If I want 
> to call functions from R.dll, I use implib /system R.lib R.dll 
> to create R.lib. Then I put pragma(lib, "R.lib"); in my .d file 
> and compile.

Thanks for walking through what you do.

I tried to create an example that more closely resembles what is 
in LearningD (see 
https://github.com/aldacron/LearningD/tree/master/Chapter09_Connecting%20D%20with%20C/clib). I created two files

clib.c
----------------
#include <stdio.h>

int some_c_function(int);

int some_c_function(int a) {
	printf("Hello, D! from C! %d\n", a);
	return a + 20;
}

and

dclib.d
-----------------
pragma(lib, `libclib.lib`);

extern(C) @nogc nothrow {
	int some_c_function(int);
}

void main()
{
	import std.stdio : writeln;
	writeln(some_c_function(10));
}

------------------
I then ran
gcc -Wall -fPIC -c clib.c
gcc -shared -o libclib.dll clib.o
implib libclib.lib libclib.dll

I'm getting an error on the implib command on my home computer. 
Maybe running it on a different computer would work.

The LearningD book says that you should compile the libraries 
with DMC on Windows, but I can't figure out how to generate a 
shared library on DMC. I didn't get the implib error for what I 
was working on before.

I feel like getting stuff to work with Windows is always such a 
hassle, but that's the only way I'll be able to use this stuff at 
work.