Filter unsupported -Wp,-U preprocessor args for zig cc

zig cc doesn't support the `-Wp,-U` pass-through form (e.g. `-Wp,-U_FORTIFY_SOURCE`
added by CMake). Strip these args in `filter_linker_arg` to fix builds of crates
like `aws-lc-sys` that use CMake internally.

Author: messense

.github/workflows/CI.yml

@@ -206,6 +206,14 @@ jobs:
 
           cargo run run --target aarch64-unknown-linux-gnu --manifest-path tests/hello-rustls/Cargo.toml
           cargo run test --target aarch64-unknown-linux-gnu --manifest-path tests/hello-rustls/Cargo.toml
+      - name: Test aws-lc-rs build
+        if: matrix.os != 'windows-latest'
+        env:
+          # See https://github.com/aws/aws-lc-rs/issues/512
+          AWS_LC_SYS_NO_ASM: "1"
+        run: |
+          cargo run zigbuild --target aarch64-unknown-linux-gnu --manifest-path tests/hello-aws-lc-rs/Cargo.toml
+          cargo run zigbuild --target aarch64-apple-darwin --manifest-path tests/hello-aws-lc-rs/Cargo.toml
       - name: Linux - Test glibc build openssl
         if: matrix.os != 'windows-latest'
         run: |

src/zig.rs

@@ -542,6 +542,16 @@ fn filter_linker_arg(
             return FilteredArg::Skip;
         }
     }
+    // zig cc only supports -Wp,-MD, -Wp,-MMD, and -Wp,-MT;
+    // strip all other -Wp, args (e.g. -Wp,-U_FORTIFY_SOURCE from CMake)
+    // https://github.com/ziglang/zig/blob/0.15.2/src/main.zig#L2798
+    if arg.starts_with("-Wp,")
+        && !arg.starts_with("-Wp,-MD")
+        && !arg.starts_with("-Wp,-MMD")
+        && !arg.starts_with("-Wp,-MT")
+    {
+        return FilteredArg::Skip;
+    }
     if arg.starts_with("-march=") {
         if target_info.is_arm() || target_info.is_i386() {
             return FilteredArg::Skip;
@@ -2288,6 +2298,32 @@ mod tests {
         }
     }
 
+    #[test]
+    fn test_filter_wp_args() {
+        let linux = Some("x86_64-unknown-linux-gnu");
+        // Unsupported -Wp, args should be removed
+        for arg in &[
+            "-Wp,-U_FORTIFY_SOURCE",
+            "-Wp,-DFOO=1",
+            "-Wp,-MF,/tmp/t.d",
+            "-Wp,-MQ,foo",
+            "-Wp,-MP",
+        ] {
+            let result = run_filter_one(arg, linux, (13, 0));
+            assert!(result.is_empty(), "{arg} should be removed");
+        }
+        // Supported -Wp, args should be kept (-MD, -MMD, -MT)
+        for arg in &["-Wp,-MD,/tmp/test.d", "-Wp,-MMD,/tmp/test.d", "-Wp,-MT,foo"] {
+            let result = run_filter_one(arg, linux, (13, 0));
+            assert_eq!(result, vec![*arg], "{arg} should be kept");
+        }
+        // bare -U and -D should be kept (zig cc supports them directly)
+        let result = run_filter_one("-U_FORTIFY_SOURCE", linux, (13, 0));
+        assert_eq!(result, vec!["-U_FORTIFY_SOURCE"]);
+        let result = run_filter_one("-DFOO=1", linux, (13, 0));
+        assert_eq!(result, vec!["-DFOO=1"]);
+    }
+
     #[test]
     fn test_filter_musl_args() {
         let musl = Some("x86_64-unknown-linux-musl");