Okay.

Author: Eclips4

Modules/cpython-sys/build.rs

@@ -97,6 +97,7 @@ fn generate_c_api_bindings(srcdir: &Path, builddir: Option<&str>, out_path: &Pat
                     }
                 } else if flag.starts_with("-I")
                     || flag.starts_with("-D")
+                    || flag.starts_with("-std=")
                     || flag.starts_with("-isystem")
                 {
                     builder = builder.clang_arg(flag);
@@ -151,11 +152,6 @@ fn generate_c_api_bindings(srcdir: &Path, builddir: Option<&str>, out_path: &Pat
     }
     builder = add_target_clang_args(builder, builddir);
 
-    // Use C11 with GNU extensions so that <stdatomic.h> is available,
-    // required by the mimalloc headers. This must be the last clang arg
-    // to ensure it is not overridden by any earlier -std= flag.
-    builder = builder.clang_arg("-std=gnu11");
-
     let bindings = builder
         .allowlist_function("_?Py.*")
         .allowlist_type("_?Py.*")

Modules/cpython-sys/wrapper.h

@@ -32,6 +32,11 @@
 #define Py_BUILD_CORE
 
 // Internal
+// Ensure C11 atomics are available for mimalloc headers.
+// Clang supports <stdatomic.h> in all C modes via __has_extension(c_atomic).
+#if !defined(__cplusplus)
+#include <stdatomic.h>
+#endif
 #include "internal/pycore_parser.h"
 #include "internal/pycore_mimalloc.h"
 #include "internal/mimalloc/mimalloc.h"