`zig cc` fails to compile simple programs on macOS Catalina and Big Sur

[carlocab]

Zig Version

0.9.0

Steps to Reproduce

Compile the following program with zig cc hello.c -o hello on macOS Catalina or Big Sur (not Monterey):

// hello.c
#include <stdio.h>
int main() {
  fprintf(stdout, "Hello, world!");
  return 0;
}

Expected Behavior

No error.

Actual Behavior

Compilation fails with the following error.

  /Library/Developer/CommandLineTools/SDKs/MacOSX11.sdk/usr/include/stdio.h:220:5: error: 'TARGET_OS_IPHONE' is not defined, evaluates to 0 [-Werror,-Wundef-prefix=TARGET_OS_]
  #if TARGET_OS_IPHONE
      ^

CI logs available at https://github.com/Homebrew/homebrew-core/actions/runs/1604777034. See Homebrew/homebrew-core#91763.

[carlocab]

Incidentally, this is the same error as in #8999.

[andrewrk]

This does not repro for me on Catalina, with a zig built from source, using homebrew-provided LLVM. Can you share any information to help us repro the issue?

[carlocab]

Thanks for having a look.

Do you have both the CLT and Xcode.app installed? If you have the CLT installed, can you try doing some combination of

export SDKROOT=/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk
export CPATH=/usr/local/include:/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk/usr/include

before trying to do zig cc?

You can also try downloading the built bottle from here. Scroll down to "Artifacts" and then click on the one labelled "bottles-10.15".

You can install the bottle with

xattr -c /path/to/zig--0.9.0.catalina.bottle.tar.gz
brew install /path/to/zig--0.9.0.catalina.bottle.tar.gz

and then run our test with brew test zig. (You might need to check out the zig PR with something like cd "$(brew --repo homebrew/core) && gh pr checkout 91763 first.)

I suspect one of the env variables we set in the test environment is causing this. Here's what might be relevant:

PKG_CONFIG_LIBDIR=/usr/local/lib/pkgconfig:/usr/local/share/pkgconfig:/usr/local/Homebrew/Library/Homebrew/os/mac/pkgconfig/12:/usr/lib/pkgconfig
MAKEFLAGS=-j4
CPPFLAGS=-F/usr/local/Frameworks -isysroot/Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk
LDFLAGS=-L/usr/local/lib -F/usr/local/Frameworks -Wl,-headerpad_max_install_names -isysroot/Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk
CMAKE_FRAMEWORK_PATH=/usr/local/Frameworks:/Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk/System/Library/Frameworks
CFLAGS=-Os -w -pipe -march=nehalem -mmacosx-version-min=12 -isysroot/Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk
CXXFLAGS=-Os -w -pipe -march=nehalem -mmacosx-version-min=12 -isysroot/Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk
OBJCFLAGS=-Os -w -pipe -march=nehalem -mmacosx-version-min=12 -isysroot/Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk
OBJCXXFLAGS=-Os -w -pipe -march=nehalem -mmacosx-version-min=12 -isysroot/Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk
OBJC=/usr/bin/clang
CC=/usr/bin/clang
OBJCXX=/usr/bin/clang++
CXX=/usr/bin/clang++
LC_CTYPE=C
CPATH=/usr/local/include:/Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk/usr/include
SDKROOT=/Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk
CMAKE_PREFIX_PATH=/Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk/usr

You can see the full list of environment variables by applying this patch to $(brew --repo homebrew/core):

diff --git a/Formula/zig.rb b/Formula/zig.rb
index 9acd19e861d..0670f2ed51b 100644
--- a/Formula/zig.rb
+++ b/Formula/zig.rb
@@ -34,6 +34,9 @@ class Zig < Formula
   end
 
   test do
+    ENV.each do |k,v|
+      puts "#{k}=#{v}"
+    end
     (testpath/"hello.zig").write <<~EOS
       const std = @import("std");
       pub fn main() !void {

[carlocab]

Based on CI at Homebrew/homebrew-core#91763, it seems that it's the CPATH setting that's the culprit. My guess is that it ends up mixing headers from Xcode and the CLT and that breaks things.

[andrewrk]

Thanks, this helps a ton! I think on our end we will start scrubbing some of these environment variables before invoking clang_main because Zig is supposed to be in charge of all include paths.

[mikdusan]

issue resolved: it was caused by an errant CPATH environment variable

[chenrui333]

issue resolved: it was caused by an errant CPATH environment variable

Did issue get resolved on zig side? Any pointers?