libstdc++: Force-inline shared_ptr::operator bool() for C++20 [PR108636]

This avoids a linker error with -fkeep-inline-functions when including
<filesystem>. We can't backport the fix from trunk because it adds an
export to the shared library. By marking the "missing" symbol
always_inline for C++20 mode we don't need a definition in the library.

libstdc++-v3/ChangeLog:

	PR libstdc++/108636
	* include/bits/shared_ptr_base.h (__shared_ptr::operator bool):
	Add always_inline attribute for C++20 and later.

diff --git a/libstdc++-v3/include/bits/shared_ptr_base.h b/libstdc++-v3/include/bits/shared_ptr_base.h
index c22b397a194675ef59ce424b6b2667724812496e..23c3b17d46f94493f16814c5c35591352804087c 100644 (file)
--- a/libstdc++-v3/include/bits/shared_ptr_base.h
+++ b/libstdc++-v3/include/bits/shared_ptr_base.h
@@ -1666,6 +1666,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       { return _M_ptr; }
 
       /// Return true if the stored pointer is not null.
+#if __cplusplus >= 202002L
+      [[__gnu__::__always_inline__]]
+#endif
       explicit operator bool() const noexcept
       { return _M_ptr != nullptr; }