Linking error from a duplicate symbol, one imported from C

[gray ridge]

I am new to zig, but am hoping to use it to consume a yacc generated parser. I'm using the very simple hoc1 language from Pike & Kernighan's "UNIX Programming Environment". Instead of the parser printing out the result, I have modified to assign the result to a global variable.

The grammar file is here: https://gist.github.com/cdcarter/cb64f5b28482f28c904119f9694d93f0#file-hoc-y
this results in the following hoc.tab.h header: https://gist.github.com/cdcarter/cb64f5b28482f28c904119f9694d93f0#file-hoc-tab-h
which I translated into zig with zig translate-c: https://gist.github.com/cdcarter/cb64f5b28482f28c904119f9694d93f0#file-hoc-zig
I then use those symbols in my main.zig: https://gist.github.com/cdcarter/cb64f5b28482f28c904119f9694d93f0#file-main-zig
finally, I build this all and used "addCSourceFile" to include the actual parser implementation: https://gist.github.com/cdcarter/cb64f5b28482f28c904119f9694d93f0#file-hoc-tab-c

This results in:

% zig build                                                                                  
MachO Flush... error(link): symbol '_result' defined multiple times
error(link):   first definition in '/Users/cdcarter/hoc/zighoc/zig-cache/o/e854fcc73548dd9fd6af4076f010bf6c/hoc.tab.o'
error(link):   next definition in '/Users/cdcarter/hoc/zighoc/zig-cache/o/c63d0ae58538b1896e72d0d704793ff4/zighoc.o'
error: MultipleSymbolDefinitions
error: zighoc...

I know I'm not doing anything too complicated, but I'm not sure where to turn next to debug this. hoc.tab.c, the C source for the parser, does not define result, its defined in the header file that I dutifully translated to zig.

I assume my mental model of importing from C is broken, but I can't figure this one out. Any advice would be appreciated!

I tried to switch to @cImport instead of running translate-c...

const std = @import("std");
const c = @cImport({
    @cInclude("hoc.tab.h");
});

pub fn main() void {
    std.debug.print("Result: {d}\n> ", .{c.result});
    _ = c.yyparse();

    std.debug.print("Result: {d}\n", .{c.result});
}
```, but this instead resulted with the compile failing entirely
```/Users/cdcarter/hoc/zighoc/main.zig:2:11: error: C import failed
const c = @cImport({
          ^~~~~~~~
referenced by:
    main: /Users/cdcarter/hoc/zighoc/main.zig:7:42
    comptime_0: /opt/homebrew/Cellar/zig/0.10.1/lib/zig/std/start.zig:59:50
    remaining reference traces hidden; use '-freference-trace' to see all reference traces
```.
Adding `-freference-trace` results in no additional reference.

[hasty vault]

The error is correct, result gets defined in the c obj and zig obj - what might be a solution
in hoc.zig

- pub export var result: f64 = 0;
+ pub extern var result: f64;

[gray ridge]

oh, sigh, of course! manually editing the generated zig works fine. and now that I think about it, of course I need to separate the definition and declarations of the symbol in the yacc, even if this were C.

thanks for pointing out the obvious. now we're off!

Manually modifying the generated zig worked, but even if I try to just declare result in the c but never assign a 0 to it, the zig is now generated as

pub export var result: f64 = @import("std").mem.zeroes(f64);

I wonder what C I need to craft to get the translator to give me the right zig...I probably won't worry about it much for now because I have something that works.

[hasty vault]

the proper way to do it is to extern double result; in the header and double result = 0; in a single c file (otherwise you'd be defining a result every time you include the (translated) header)

[gray ridge]

Yep, that does it! curiously, the cImport version still fails. but the translate works perfectly, thank you!

[hasty vault]

that's because cImport requires the file to be in within an -I
(exe.addIncludePath("./src"); if using build.zig)