From 71cfd423e3eb495676c9cd47151089e6dd4b9570 Mon Sep 17 00:00:00 2001
From: Jasmine Tang <jjasmine@igalia.com>
Date: Sun, 17 May 2026 18:43:35 -0700
Subject: [PATCH] Add -fno-cxx-modules to clang's known -Xclang flags

Downstream Bazel's C++ toolchain passes `-Xclang -fno-cxx-modules` in its
compiler sanity checks. Since -fno-cxx-modules
wasn't in sccache's known flag list, the xclang argument parser in
gcc.rs treated it as an UnknownFlag and bailed with CannotCache.
---
 src/compiler/clang.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/compiler/clang.rs b/src/compiler/clang.rs
index e6294d524..399e72424 100644
--- a/src/compiler/clang.rs
+++ b/src/compiler/clang.rs
@@ -212,6 +212,7 @@ counted_array!(pub static ARGS: [ArgInfo<gcc::ArgData>; _] = [
     take_arg!("-fmodule-output", OsString, Concatenated, ClangModuleOutput),
     flag!("-fmodules-reduced-bmi", PassThroughFlag),
     flag!("-fno-color-diagnostics", NoDiagnosticsColorFlag),
+    flag!("-fno-cxx-modules", PassThroughFlag),
     flag!("-fno-pch-timestamp", PassThroughFlag),
     flag!("-fno-profile-instr-generate", TooHardFlag),
     flag!("-fno-profile-instr-use", TooHardFlag),