[PATCH 1/2] compiler_types: Ensure __diag_clang() is always available

[Nathan Chancellor <nathan@kernel.org>]

Attempting to use __diag_clang() and build with GCC results in a build
error:

  include/linux/compiler_types.h:468:38: error: 'ignore' undeclared (first use in this function); did you mean 'inode'?
    468 |         __diag_ ## compiler(version, ignore, option)
        |                                      ^~~~~~

This error occurs because __diag_clang() is only defined in
compiler-clang.h, which is only included when using clang as the
compiler. This error has not been seen before because __diag_clang() has
only been used in __diag_ignore_all(), which is defined in both
compiler-clang.h and compiler-gcc.h.

Add an empty stub for __diag_clang() in compiler_types.h, so that it is
always defined and just becomes a no-op when using GCC.

Fixes: f014a00bbeb0 ("compiler-clang.h: Add __diag infrastructure for clang")
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
 include/linux/compiler_types.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index 3e64ec0f7ac8..fb0c3ff5497d 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -461,6 +461,10 @@ struct ftrace_likely_data {
 #define __diag_GCC(version, severity, string)
 #endif
 
+#ifndef __diag_clang
+#define __diag_clang(version, severity, string)
+#endif
+
 #define __diag_push()	__diag(push)
 #define __diag_pop()	__diag(pop)
 

-- 
2.44.0