macho: allow undefined symbols in dylibs

We now respect both `-fallow-shlib-undefined` and
`-Wl,"-undefined=dynamic_lookup"` flags. This is the first step
towards solving issues #8180 and #3000. We currently do not expose
any other ld64 equivalent flag for `-undefined` flag - we basically
throw an error should the user specify a different flag. Support for
those is conditional on closing #8180. As a result of this change,
it is now possible to generate a valid native Node.js addon with Zig
for macOS.

1 files changed, 10 insertions, 0 deletions

diff --git a/src/main.zig b/src/main.zig
index c29a272660..761935c897 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -1703,6 +1703,16 @@ fn buildOutputType(
                     }
                     emit_implib = .{ .yes = linker_args.items[i] };
                     emit_implib_arg_provided = true;
+                } else if (mem.eql(u8, arg, "-undefined")) {
+                    i += 1;
+                    if (i >= linker_args.items.len) {
+                        fatal("expected linker arg after '{s}'", .{arg});
+                    }
+                    if (mem.eql(u8, "dynamic_lookup", linker_args.items[i])) {
+                        linker_allow_shlib_undefined = true;
+                    } else {
+                        fatal("unsupported -undefined option '{s}'", .{linker_args.items[i]});
+                    }
                 } else {
                     warn("unsupported linker arg: {s}", .{arg});
                 }