Re: Intro to calling C libraries
Sweet!
Re: Intro to calling C libraries
On Thursday, 20 February 2025 at 21:10:29 UTC, Ian wrote: ... Another cool aspect of ImportC is that you can use the D compiler's header generator to generate .di files from C sources - i.e. semi-automatic, native binding generation! I say semi-automatic since it misses out things like macros, and unfortunately the header generator actually spits out invalid D code... e.g. I have a script [here](https://github.com/Juptune/juptune/blob/master/devops/scripts/gen-libsodium-di.bash) to generate bindings for libsodium.
Re: Intro to calling C libraries
On Thursday, 20 February 2025 at 20:09:29 UTC, Ian wrote:
What is the recommended documentation or introductory material
on how to call C libraries from D? I've seen it done in GtkD
(for GTK3) and I have heard of -betterC, but it's all a little
overwhelming. (I'm an experienced C programmer but new to D)
Ian, You do not need importC in order to interface with a C
library. A good starting read would be:
https://dlang.org/spec/interfaceToC.html
If you know the C code (or C library you want to interface with)
it is relatively easy to use it directly from D. The real
challenge sometimes is to "port" complex C macros to D. The
following page is an essential read:
https://dlang.org/articles/ctod.html
Here is a simple start project. Let's call liblz4's
LZ4_versionNumber() function to get the version of the library,
and print it out:
```d
module lz4version;
import std.stdio;
// https://github.com/lz4/lz4/blob/dev/lib/lz4.h line 142
extern(C) int LZ4_versionNumber();
int main() {
int lz4Version = LZ4_versionNumber();
int m = lz4Version / 1;
lz4Version = lz4Version % 1;
int n = lz4Version / 100;
lz4Version = lz4Version % 100;
int r = lz4Version;
writeln("LZ4 library version: ", m, ".", n, ".",r);
return 0;
}
```
Save this code to the lz4version.d file, and let's compile and
link to lz4version executable with:
`gdc -o lz4version lz4version.d -llz4`
Now, let's run it:
```
shell» ./lz4version
LZ4 library version: 1.9.4
```
Indeed that is the version of the LZ4 library I have on my local
Fedora 40 workstation: `/usr/lib64/liblz4.so.1.9.4`
Re: Intro to calling C libraries
On Thursday, 20 February 2025 at 21:05:40 UTC, Lance Bachmeier wrote: Normally, you should be using ImportC. Look at the quick example from the spec: https://dlang.org/spec/importc.html#examples The first line of hello.c looks like this: ``` #include ``` When ImportC compiles a C file, it runs the C preprocessor and does all the including you need. But rather than stdio.h, you can compile a C file that includes all the C headers you need. That's all you have to do. You can use the usual preprocessor calls like -I by using the -P switch: https://dlang.org/spec/importc.html#auto-cpp Assuming ImportC works with your C headers, that's everything you need. Perfect! I'll try this. Thank you.
Re: Intro to calling C libraries
On Thursday, 20 February 2025 at 20:09:29 UTC, Ian wrote: Hi, What is the recommended documentation or introductory material on how to call C libraries from D? I've seen it done in GtkD (for GTK3) and I have heard of -betterC, but it's all a little overwhelming. (I'm an experienced C programmer but new to D) Cheers, Ian Normally, you should be using ImportC. Look at the quick example from the spec: https://dlang.org/spec/importc.html#examples The first line of hello.c looks like this: ``` #include ``` When ImportC compiles a C file, it runs the C preprocessor and does all the including you need. But rather than stdio.h, you can compile a C file that includes all the C headers you need. That's all you have to do. You can use the usual preprocessor calls like -I by using the -P switch: https://dlang.org/spec/importc.html#auto-cpp Assuming ImportC works with your C headers, that's everything you need. If ImportC doesn't work (as may be the case due to C extensions and preprocessor hacks), you should use dpp or dstep: https://dlang.org/spec/importc.html#dpp
