Forward framework dirs to embedded clang in addition to linker on macOS

[gustavolsson]

Problem

It seems that the default system/framework paths on macOS is a bit off currently (issue #2319 , #2208). Figuring out the best way to determine these paths is a bit over my head but while trying to work around the issue I do think I've encountered a bug in how zig passes arguments to zig cc:

It seems like if you use exe.addFrameworkDir(path), the path is only forwarded to the linker (-F path), not the embedded clang (-iframework path).

Proposed solution

Forward the argument to embedded clang in addition to the linker.

Feel free to close this if my reasoning is wrong :)

To reproduce

Here is an example project: https://github.com/gustavolsson/zig-sokol-test

I'm trying to build the OpenGL app on macOS (old one 10.13.16) and get zig cc errors about Cocoa.h not being found. I want to work around the issue by explicitly specifying the path to Cocoa.framework on my specific machine, /System/Library/Frameworks, using exe.addFrameworkDir(...):

exe.addFrameworkDir("/System/Library/Frameworks");
exe.linkFramework("Cocoa");
exe.linkFramework("OpenGL");
exe.enableSystemLinkerHack(); // Uses system linker instead of embedded ldd, I think...

const c_args = [2][]const u8{
    "-ObjC",
    "-fobjc-arc",
};
exe.addCSourceFile("src/sokol.c", c_args);
exe.addCSourceFile("src/clear-sapp.c", c_args);

(Note that I also enable the system linker hack because once zig cc succeeds the linking crashes due to MachO problems, which is way over my head and I want to show that the proposed fix manages to build the code)

I get the following error:

In file included from /Users/gustav/Documents/Development/zig-ws/zig-sokol-test/src/sokol.c:10:
/Users/gustav/Documents/Development/zig-ws/zig-sokol-test/src/sokol_app.h:1088:10: fatal error:
      'Cocoa/Cocoa.h' file not found
#include 
         ^~~~~~~~~~~~~~~
1 error generated.

The following command failed:
/usr/local/Cellar/zig/HEAD-9a18db8/bin/zig cc -MD -MV -MF /Users/gustav/Documents/Development/zig-ws/zig-sokol-test/zig-cache/tmp/Ede7tHOXwhUx-sokol.o.d -nostdinc -fno-spell-checking -isystem /usr/local/Cellar/zig/HEAD-9a18db8/lib/zig/include -isystem /usr/include -march=native -g -fno-omit-frame-pointer -D_DEBUG -fstack-protector-strong --param ssp-buffer-size=4
-fPIC -o /Users/gustav/Documents/Development/zig-ws/zig-sokol-test/zig-cache/tmp/Ede7tHOXwhUx-sokol.o -c /Users/gustav/Documents/Development/zig-ws/zig-sokol-test/src/sokol.c -ObjC -fobjc-arc

The following command exited with error code 1:
/usr/local/Cellar/zig/HEAD-9a18db8/bin/zig build-exe --c-source -ObjC -fobjc-arc /Users/gustav/Documents/Development/zig-ws/zig-sokol-test/src/sokol.c --c-source -ObjC -fobjc-arc /Users/gustav/Documents/Development/zig-ws/zig-sokol-test/src/clear-sapp.c --cache-dir /Users/gustav/Documents/Development/zig-ws/zig-sokol-test/zig-cache --name zig-sokol-test
-F /System/Library/Frameworks -framework OpenGL -framework Cocoa --system-linker-hack --cache on

Build failed. The following command failed:
...

Note that the zig cc command does not include -iframework /System/Library/Frameworks even though it exists in the zig build-exe command.

After the proposed change in main.cpp I can successfully build the app. zig build --verbose-cc outputs the following:

/Users/gustav/Documents/Development/zig-ws/zig/build/bin/zig cc -MD -MV -MF /Users/gustav/Documents/Development/zig-ws/zig-sokol-test/zig-cache/tmp/B8D6I_DPJVzG-sokol.o.d -nostdinc -fno-spell-checking -isystem /Users/gustav/Documents/Development/zig-ws/zig/build/lib/zig/include -isystem /usr/include -march=native -g -fno-omit-frame-pointer -D_DEBUG -fstack-protector-strong --param ssp-buffer-size=4
-fPIC -iframework /System/Library/Frameworks -o /Users/gustav/Documents/Development/zig-ws/zig-sokol-test/zig-cache/tmp/B8D6I_DPJVzG-sokol.o -c /Users/gustav/Documents/Development/zig-ws/zig-sokol-test/src/sokol.c -ObjC -fobjc-arc

[andrewrk]

Thanks for the detailed writeup and the patch!

[floooh]

I'm having "partial success" with @gustavolsson's fix:

In order to find the system framework headers on macOS Catalina / Xcode11 I need to give the build system the complete path to the macOS frameworks directory (which is the output of xcrun --show-sdk-path + /System/Library/Frameworks).

My build.zig now looks like this (with a hardcoded frameworks path):

https://github.com/floooh/sokol-zig/blob/3928f91e2e8e63cae15aa195d77ec050ef024677/build.zig

The enableSystemLinkerHack() is still needed, but that's an unrelated problem.

Unfortunately my exe now crashes with a segfault, not sure whether this is because of the build or another recent change in the HEAD version. I'll try to investigate in the evening.

[floooh]

Ok, the segfault I'm getting was related to my handling of optional function pointers.

So the two things that are currently still necessary on macOS:

• pass the absolute macOS SDK Frameworks path to addFrameworkDir()
• use enableSystemLinkerHack()

...but I can definitely continue now with my sokol experiments, thanks Gustav! :)

[andrewrk]

pass the absolute macOS SDK Frameworks path to addFrameworkDir()

This will be solved with #2041, in which linking against a system library (or framework) will run target-specific logic (potentially even xcrun --show-sdk-path for example) to find and otherwise set up all the paths correctly.

use enableSystemLinkerHack()

Sadly the fix for this is a long way out and it involves writing our own linker. #1535

[floooh]

This will be solved with #2041...

For now I've changed the build script to call xcrun myself and extract the path from the result: https://github.com/floooh/sokol-zig/blob/f2a50e7dd5aeeddd82256d6c757cda3bec08c640/build.zig#L7-L20

FYI: this is what the updated sokol-gfx clear-sample looks like (just opens a window and clears the framebuffer with dynamic colors, via the Metal backend):

https://github.com/floooh/sokol-zig/blob/master/src/main.zig

A nice (recent?) zig addition is the [_], in the new struct initialization with default-values, this allows to omit any "remaining" struct items which should be initialized with default values (I hope that's intended):

https://github.com/floooh/sokol-zig/blob/master/src/main.zig

Compared to the C99 version:

https://github.com/floooh/sokol-samples/blob/master/sapp/clear-sapp.c