[libcxx] Apply pragma for silencing warning when building with clang-cl too

[mstorsjo]

Summary

This silences warnings about unused functions (in an anonymous
namespace).

[curdeius]

Indeed. clang-cl does not define __GNUC__, only __clang__.
LGTM.

[ldionne]

I assume this warning is necessary because some functions are defined but not used in different configurations? Like a function that would be always defined but only used when building for Windows or the opposite?

[mstorsjo]

In D98036#2606546, @ldionne wrote:

I assume this warning is necessary because some functions are defined but not used in different configurations? Like a function that would be always defined but only used when building for Windows or the opposite?

No, this is a header under src/filesystem, included by two cpp files in src/filesystem, that contains an anonymous namespace with helper functions (to avoid creating externally visible symbols) used by both src files - but not all of the functions are used by both src files. (And there's one function with multiple overloads, where one overload currently doesn't seem to be used at all, see const path::value_type* unwrap(path::string_type const& s) { return s.c_str(); } on line 111.)

[ldionne]

In D98036#2606601, @mstorsjo wrote:

In D98036#2606546, @ldionne wrote:

I assume this warning is necessary because some functions are defined but not used in different configurations? Like a function that would be always defined but only used when building for Windows or the opposite?

No, this is a header under src/filesystem, included by two cpp files in src/filesystem, that contains an anonymous namespace with helper functions (to avoid creating externally visible symbols) used by both src files - but not all of the functions are used by both src files. (And there's one function with multiple overloads, where one overload currently doesn't seem to be used at all, see const path::value_type* unwrap(path::string_type const& s) { return s.c_str(); } on line 111.)

Got it, thanks. We could consider removing that overload if it's unused (feel free to do that as a NFC change if you want).

libcxx/src/filesystem/filesystem_common.h

 #if !defined(__APPLE__)
 // We can use the presence of UTIME_OMIT to detect platforms that provide
 // utimensat.
 #if defined(UTIME_OMIT)
 #define _LIBCPP_USE_UTIMENSAT
 #endif
 #endif
 
-#if defined(__GNUC__)
+#if defined(__GNUC__) || defined(__clang__)
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wunused-function"
 #endif
 
 #if defined(_LIBCPP_WIN32API)
 #define PS(x) (L##x)
 #else
 #define PS(x) (x)