Linking with objective-c causes bus error on macOS

[schroffl]

I'm trying to write some macOS-specific code in objective-c and include that in my Zig application. However, the following simple setup causes a crash when building.

build.zig

const Builder = @import("std").build.Builder;

pub fn build(b: *Builder) void {
    var exe = b.addExecutable("zig-macos-objc", "src/main.zig");

    // Compiles the objective-c code into `./objc.o`
    var compile_objc = b.addSystemCommand(&[_][]const u8{
        "clang",
        "-c",
        "src/objc.m",
    });

    exe.addFrameworkDir("/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/System/Library/Frameworks/");
    exe.linkFramework("Foundation");
    exe.addObjectFile("./objc.o");
    exe.step.dependOn(&compile_objc.step);

    // Everything from here on is as emitted by `zig init-exe`

    const target = b.standardTargetOptions(.{});
    const mode = b.standardReleaseOptions();

    exe.setTarget(target);
    exe.setBuildMode(mode);
    exe.install();

    const run_cmd = exe.run();
    run_cmd.step.dependOn(b.getInstallStep());

    const run_step = b.step("run", "Run the app");
    run_step.dependOn(&run_cmd.step);
}

src/objc.m

#import <Foundation/Foundation.h>

extern void my_objc_function() {
    NSLog(@"All your codebase are belong to us.");
}

src/main.zig

extern fn my_objc_function() void;

pub fn main() void {
    my_objc_function();
}

This is what caused the crash according to the macOS Console:

Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
0   libsystem_platform.dylib      	0x00007fff70973470 _platform_memcmp + 208
1   zig                           	0x000000010c63301e lld::mach_o::normalized::MachOFileLayout::buildFileOffsets() + 894

---

Zig-Version: 0.6.0+c49435f76
macOS Version: 10.15.6

If any other information like the output fromzig build --verbose-link is needed I can add that as well.

---

Edit: By manually using ld I was able to link a working binary.

[andrewrk]

#5828 (comment)

[fabioarnold]

Just tried this with Zig version 0.7.1+f75d4cbe5 and it works. I'm on macOS 11.1 arm64. @kubkon can this issue be closed?

Edit:
Had to add -isysroot in build.zig

const Builder = @import("std").build.Builder;

pub fn build(b: *Builder) void {
    var exe = b.addExecutable("zig-macos-objc", "src/main.zig");

    // Compiles the objective-c code into `./objc.o`
    var compile_objc = b.addSystemCommand(&[_][]const u8{
        "clang",
        "-isysroot", "/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk",
        "-c", "src/objc.m",
    });

    exe.addFrameworkDir("/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/System/Library/Frameworks/");
    exe.linkFramework("Foundation");
    exe.addObjectFile("./objc.o");
    exe.step.dependOn(&compile_objc.step);

    // Everything from here on is as emitted by `zig init-exe`

    const target = b.standardTargetOptions(.{});
    const mode = b.standardReleaseOptions();

    exe.setTarget(target);
    exe.setBuildMode(mode);
    exe.install();

    const run_cmd = exe.run();
    run_cmd.step.dependOn(b.getInstallStep());

    const run_step = b.step("run", "Run the app");
    run_step.dependOn(&run_cmd.step);
}

[kubkon]

Hmm, I'm surprised this works for you @fabioarnold. I get a linker error:

warning(link): unexpected LLD stderr:
ld64.lld: error: Unable to find framework for -framework Foundation

attempt to unwrap error: FileNotFound
/Users/kubkon/dev/zig/src/main.zig:2027:87: 0x1027caae3 in main.cmdTranslateC (zig1)
        const new_argv_with_sentinel = try arena.alloc(?[*:0]const u8, argv.items.len + 1);
                                                                                      ^
/Users/kubkon/dev/zig/src/main.zig:1787:31: 0x10272057b in main.buildOutputType (zig1)
            .no => break :blk .none,
                              ^
/Users/kubkon/dev/zig/src/main.zig:125:49: 0x1026f98d7 in main.mainArgs (zig1)
    if (std.process.can_execv and std.os.getenvZ("ZIG_IS_DETECTING_LIBC_PATHS") != null) {
                                                ^
/Users/kubkon/dev/zig/lib/std/heap.zig:142:46: 0x1026f6c63 in std.heap.CAllocator.resize (zig1)
            const full_len = alignedAllocSize(buf.ptr);
                                             ^
/Users/kubkon/dev/zig/lib/std/heap.zig:142:46: 0x1026f6c63 in std.heap.CAllocator.resize (zig1)
            const full_len = alignedAllocSize(buf.ptr);
                                             ^
/Users/kubkon/dev/zig/lib/std/heap.zig:142:46: 0x1026f6c63 in std.heap.CAllocator.resize (zig1)
            const full_len = alignedAllocSize(buf.ptr);
                                             ^
/Users/kubkon/dev/zig/lib/std/heap.zig:142:46: 0x1026f6c63 in std.heap.CAllocator.resize (zig1)
            const full_len = alignedAllocSize(buf.ptr);
                                             ^
/Users/kubkon/dev/zig/lib/std/array_list.zig:151:25: 0x10293536f in std.array_list.ArrayListAligned(std.dwarf.FileEntry,null).append (zig1)
            new_item_ptr.* = item;
                        ^
/Users/kubkon/dev/zig/lib/std/array_list.zig:393:0: 0x1028aa693 in std.array_list.ArrayListAlignedUnmanaged(u8,null).deinit (zig1)
        pub fn deinit(self: *Self, allocator: *Allocator) void {

/Users/kubkon/dev/zig/lib/std/crypto/sha2.zig:148:14: 0x1028aa3cb in std.crypto.sha2.Sha2x32((struct std.crypto.sha2.Sha2Params32 constant)).final (zig1)
            d.buf_len += 1;
             ^
/Users/kubkon/dev/zig/lib/std/crypto/sha2.zig:144:30: 0x1028aa35f in std.crypto.sha2.Sha2x32((struct std.crypto.sha2.Sha2Params32 constant)).final (zig1)
            mem.set(u8, d.buf[d.buf_len..], 0);
                             ^
/Users/kubkon/dev/zig/lib/std/base64.zig:54:23: 0x10287029b in std.base64.Base64Encoder.encode (zig1)
            out_index += 1;
                      ^
/Users/kubkon/dev/zig/lib/std/crypto/sha2.zig:272:185: 0x102a24fbb in std.crypto.sha2.Sha2x32((struct std.crypto.sha2.Sha2Params32 constant)).round (zig1)
                v[r.h] = v[r.h] +% (math.rotr(u32, v[r.a], @as(u32, 2)) ^ math.rotr(u32, v[r.a], @as(u32, 13)) ^ math.rotr(u32, v[r.a], @as(u32, 22))) +% ((v[r.a] & (v[r.b] | v[r.c])) | (v[r.b] & v[r.c]));
                                                                                                                                                                                        ^
/Users/kubkon/dev/zig/src/link/MachO/CodeSignature.zig:163:32: 0x1028aa893 in link.MachO.CodeSignature.writeHeader (zig1)
    mem.writeIntBig(u32, buffer[8..12], self.inner.count);
                               ^
/Users/kubkon/dev/zig/lib/std/fmt.zig:360:13: 0x10282204b in std.fmt.format (zig1)
            writer,
            ^
/Users/kubkon/dev/zig/lib/std/heap.zig:142:46: 0x1026f6c63 in std.heap.CAllocator.resize (zig1)
            const full_len = alignedAllocSize(buf.ptr);
                                             ^
/Users/kubkon/dev/zig/lib/std/heap.zig:142:46: 0x1026f6c63 in std.heap.CAllocator.resize (zig1)
            const full_len = alignedAllocSize(buf.ptr);
                                             ^
/Users/kubkon/dev/zig/lib/std/heap.zig:142:46: 0x1026f6c63 in std.heap.CAllocator.resize (zig1)
            const full_len = alignedAllocSize(buf.ptr);
                                             ^
/Users/kubkon/dev/zig/lib/std/array_list.zig:151:25: 0x10293536f in std.array_list.ArrayListAligned(std.dwarf.FileEntry,null).append (zig1)
            new_item_ptr.* = item;
                        ^
/Users/kubkon/dev/zig/lib/std/heap/arena_allocator.zig:73:42: 0x1027b4dcb in std.heap.arena_allocator.ArenaAllocator.alloc (zig1)
            const cur_buf = cur_node.data[@sizeOf(BufNode)..];
                                         ^
/Users/kubkon/dev/zig/lib/std/array_list.zig:151:25: 0x10293536f in std.array_list.ArrayListAligned(std.dwarf.FileEntry,null).append (zig1)
            new_item_ptr.* = item;
                        ^
/Users/kubkon/dev/zig/lib/std/heap.zig:142:46: 0x1026f6c63 in std.heap.CAllocator.resize (zig1)
            const full_len = alignedAllocSize(buf.ptr);
                                             ^
/Users/kubkon/dev/zig/lib/std/array_list.zig:151:25: 0x10293536f in std.array_list.ArrayListAligned(std.dwarf.FileEntry,null).append (zig1)
            new_item_ptr.* = item;
                        ^
/Users/kubkon/dev/zig/lib/std/heap.zig:142:46: 0x1026f6c63 in std.heap.CAllocator.resize (zig1)
            const full_len = alignedAllocSize(buf.ptr);
                                             ^
/Users/kubkon/dev/zig/lib/std/array_list.zig:151:25: 0x10293536f in std.array_list.ArrayListAligned(std.dwarf.FileEntry,null).append (zig1)
            new_item_ptr.* = item;
                        ^
/Users/kubkon/dev/zig/lib/std/Progress.zig:281:92: 0x1028f76cb in std.Progress.bufWrite (zig1)
fn bufWrite(self: *Progress, end: *usize, comptime format: []const u8, args: anytype) void {
                                                                                           ^
/Users/kubkon/dev/zig/lib/std/fs.zig:918:64: 0x10277facb in std.fs.Dir.createFileZ (zig1)
            _ = os.fcntl(fd, os.F_SETFL, fl_flags) catch |err| switch (err) {
                                                               ^
/Users/kubkon/dev/zig/lib/std/debug.zig:62:38: 0x102779f97 in std.debug.print (zig1)
    const held = stderr_mutex.acquire();
                                     ^
/Users/kubkon/dev/zig/src/link/MachO.zig:670:32: 0x102885faf in link.MachO.linkWithLLD (zig1)
                try argv.append("-rpath");
                               ^
/Users/kubkon/dev/zig/lib/std/fs.zig:1877:24: 0x10286d42f in std.fs.Dir.copyFile (zig1)
            const st = try in_file.stat();
                       ^
/Users/kubkon/dev/zig/src/Compilation.zig:1511:39: 0x1028292db in Compilation.performAllTheWork (zig1)
                            try module.failed_decls.ensureCapacity(module.gpa, module.failed_decls.items().len + 1);
                                      ^
/Users/kubkon/dev/zig/lib/std/fmt.zig:359:13: 0x1028228fb in std.fmt.format (zig1)
            options,
            ^
???:?:?: 0x1068ca3ab in ___zig_fail_unwrap (???)
/Users/kubkon/dev/zig/lib/std/debug.zig:0:13: 0x1026f9497 in std.debug.panicExtra (zig1)
???:?:?: 0x19cea4f33 in ??? (???)
Panicked during a panic. Aborting.

Are you using the system linker by any chance, i.e., have this var set ZIG_SYSTEM_LINKER_HACK=1?

[fabioarnold]

You're right, sorry!
I had changed the line in my shell rc to export ZIG_SYSTEM_LINKER_HACK=0 and the linker hack was still enabled. Commenting out the line lead to the link error you mentioned.

[kubkon]

Thanks for confirming @fabioarnold!

[kubkon]

Fixed in #9229.