ctod

GitHub: https://github.com/dkorpel/ctod
Dub: https://code.dlang.org/packages/ctod

In the summer of 2020, before ImportC, I wrote a tool to help me with my D translations of C libraries: glfw-d and libsoundio-d. I wanted to publish it at some point but kind of forgot about it, until Steven Schveighoffer asked about it last week for his D translation of raylib. That made me inspired to work on it again, and I finally fixed the Windows build, so I want to share it now.

It uses tree-sitter-c to parse .c or .h files including preprocessor directives, and then replaces C syntax patterns with roughly equivalent D patterns wherever it needs and can. Because tree-sitter is very good at error-recovery, it will always output a best-effort translated .d file, no matter the content of the .c file.

Example input file main.c:

#include <stdio.h>

#define TAU 6.283185307179586476925

int main(void) {
    char buf[32];
    sprintf(buf, "tau = %f\n", TAU);
    Wait, this line is not C syntax 🤔
    return 0;
}

Output main.d:

module main;
@nogc nothrow:
extern(C): __gshared:

public import core.stdc.stdio;

enum TAU = 6.283185307179586476925;

int main() {
    char[32] buf;
    sprintf(buf.ptr, "tau = %f\n", TAU);
    Wait, this_ line is_; not C syntax 🤔
    return 0;
}

The output is supposed to be a good starting point for manual translation: tedious syntax changes are done for you, but you're left with the task of translating (non-trivial) macros, fixing errors because of D's stricter type system, and other misc things ctod doesn't translate properly yet (see also issues on GitHub 🙂).

With the rise of ImportC the use cases for this tool decrease, but in case you still find yourself translating C to D, I hope this is of use to you!

On Thursday, 13 October 2022 at 19:18:07 UTC, Dennis wrote:

Looks like it could be a nice addition to the toolbox

WOW that's pretty cool!!

It was always time consuming having to manually port C code, your tool will be very helpful!

Thanks a lot for sharing!

On Thursday, 13 October 2022 at 19:18:07 UTC, Dennis wrote:

#include <stdio.h>

#define TAU 6.283185307179586476925

int main(void) {
    char buf[32];
    sprintf(buf, "tau = %f\n", TAU);
    Wait, this line is not C syntax 🤔
    return 0;
}

module main;
@nogc nothrow:
extern(C): __gshared:

public import core.stdc.stdio;

enum TAU = 6.283185307179586476925;

int main() {
    char[32] buf;
    sprintf(buf.ptr, "tau = %f\n", TAU);
    Wait, this_ line is_; not C syntax 🤔
    return 0;
}

This is cool, I once did a port of DWM (tiling X window manager) to D because I like DWM, I wanted to learn D from within a code base I knew reasonably well and I wanted a pure D window manager, why not?

It was quite tedious though and DWM is pretty clean concise C code. As an experiment I just did it again with this tool to try it out and it was fantastic. For that small code base it only took about 15min to port and get compiling and a few more to fix the two minor runtime issues. Without this tool it took several hours to get compiling and then several more to nail down and fix all the runtime bugs.

Thanks!