[gcc r14-3104] libstdc++: Suppress clang -Wc99-extensions warnings in <complex>

[Jonathan Wakely]

https://gcc.gnu.org/g:798b1f04762c84b7cf38c4af5aba1b52823864ba

commit r14-3104-g798b1f04762c84b7cf38c4af5aba1b52823864ba
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Tue Aug 8 22:19:49 2023 +0100

    libstdc++: Suppress clang -Wc99-extensions warnings in <complex>
    
    This prevents Clang from warning about the use of the non-standard
    __complex__ keyword.
    
    libstdc++-v3/ChangeLog:
    
            * include/std/complex: Add diagnostic pragma for clang.

Diff:
---
 libstdc++-v3/include/std/complex | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/libstdc++-v3/include/std/complex b/libstdc++-v3/include/std/complex
index 0ba2167bf022..a4abe9aa96a9 100644
--- a/libstdc++-v3/include/std/complex
+++ b/libstdc++-v3/include/std/complex
@@ -47,6 +47,11 @@
 // Get rid of a macro possibly defined in <complex.h>
 #undef complex
 
+#ifdef __clang__
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wc99-extensions"
+#endif
+
 #if __cplusplus > 201703L
 # define __cpp_lib_constexpr_complex 201711L
 #endif
@@ -2642,4 +2647,8 @@ _GLIBCXX_END_NAMESPACE_VERSION
 
 #endif  // C++11
 
+#ifdef __clang__
+#pragma clang diagnostic pop
+#endif
+
 #endif  /* _GLIBCXX_COMPLEX */