cImport namespacing is too strict for C structs across multiple zig files

[pluick]

Zig Version

0.10.0-dev.7729+b88151e0e

Steps to Reproduce

File struct.h

typedef struct astruct {
        int id;
} astruct;
void printa(astruct);

File struct.c

include "struct.h"
void printa(astruct a) { }

File main.zig

const c = @cImport({ @cInclude("struct.h"); });
const other = @import("other.zig");

pub const astruct = c.astruct;

pub fn main() anyerror!void {
    var a = astruct {.id = 4};
    other.pa(a);
}

File other.zig

const std = @import("std");
const main = @import("main.zig");
const c = @cImport({ @cInclude("struct.h"); });

// This would fail
//comptime { std.debug.assert( main.astruct == c.astruct ); }

pub fn pa(a: main.astruct) void {
    c.printa(a);
}

And then attempt to compile the code.

Expected Behavior

Successful compilation - this kind of aliasing can be done with Zig structs, so I would expect the same from c structs.

Actual Behavior

Compilation fails with this error message:

./src/other.zig:9:14: error: expected type '.cimport:3:11.struct_astruct', found '.cimport:1:11.struct_astruct'
    c.printa(a);
             ^
./zig-cache/o/05ef4e7a090cb6b35ba9a3f8b92c62a6/cimport.zig:55:28: note: .cimport:3:11.struct_astruct declared here
pub const struct_astruct = extern struct {
                           ^
./zig-cache/o/05ef4e7a090cb6b35ba9a3f8b92c62a6/cimport.zig:55:28: note: .cimport:1:11.struct_astruct declared here
pub const struct_astruct = extern struct {

Which appears to be referencing different declarations of the same c struct (.cimport:1 vs .cimport:3)

[pluick]

Some extra info:

• if the aliasing is done within the same zig file, it will not fail
• this also fails if c.astruct is wrapped inside a zig struct, and then passed to a separate zig file
• My use case that discovered this is writing a binding layer to c code

[Vexu]

Each @cImport causes the file to be translated again creating new, distinct types. This is why it is advisable to only have one @cImport in your project. See the documentation here https://ziglang.org/documentation/master/#cImport.

Related #4017