ctod: a tool that translates C code to D

[stew]

On Thursday, 13 October 2022 at 19:18:07 UTC, Dennis wrote:
> # 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](https://code.dlang.org/packages/glfw-d) and 
> [libsoundio-d](https://code.dlang.org/packages/libsoundio-d). I 
> wanted to publish it at some point but kind of forgot about it, 
> until [Steven Schveighoffer asked about 
> it](https://github.com/dkorpel/glfw-d/discussions/18) last week 
> for his [D translation of 
> raylib](https://github.com/schveiguy/draylib). 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](https://github.com/tree-sitter/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:
> ```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:
> ```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](https://github.com/dkorpel/ctod/issues) 🙂).
>
> 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!

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!