Automatically add includes for cimports

[Sobeston]

Currently if I have a folder that contains two files: main.c and main.zig, the following code inside main.zig does not work:

const c = @cImport(
    @cInclude("main.c"),
);

This is because our way of including C files is modeled after how C does it (which makes total sense). However, this is a bad user experience and frankly unsatisfying.

What I propose here is automatically adding includes for cimports - one include at the directory of cimporting zig file.

[SpexGuy]

We could do the C thing and have two:

@cInclude("foo.h"), // searches this directory first
@cInclude(<foo.h>), // searches only include directories

(but please don't actually do this)

---

In all seriousness though, the C compatibility features are there to match C. Since C's behavior for an include with quotes is to search the file's directory, and we use quotes (albeit for different reasons), I think we should do the same thing as C here and search the file's directory before searching include directories.

[andrewrk]

@Sobeston I'm happy to re-open this if you clarify the proposal more. As it stands I don't really understand what it is suggesting. Can you include a full example with all files involved and the command line you expect to execute?

[SpexGuy]

Here's a complete example:

// src/foo.c
#include "foo.h"

// src/foo.h
#define FOO 1

// src/foo.zig
comptime {
  _ = @cImport({
    @cInclude("foo.h");
  });
}

The command zig cc src/foo.c -c -o foo.o succeeds, because #include "foo.h" searches in the directory containing the .c file first. But the command zig build-obj src/foo.zig -lc fails, because src is not specified on the include path. The proposal here is to change the search path of @cInclude to start with the directory containing the .zig file.

[andrewrk]

Thanks!

[andrewrk]

Solved by moving @cImport to the build system. #20630