Extended Description

GCC handles _LIBCPP_INLINE_VISIBILITY differently than Clang. In particular when the attributes are applied to symbols which are externally instantiated.

For example in the reproducer below Clang will emit both 'foo' and 'bar' with default visibility while GCC only emits a non-hidden 'foo'.

// RUN: g++ -std=c++11 -shared -O3 test.cpp && sym_extract.py a.out
// RUN: clang++ -std=c++11 -shared -O3 test.cpp && sym_extract.py a.out
template
struct Foo {
void foo();
void bar();
};

template
void Foo::foo() {}

template
inline attribute((visibility("hidden"), always_inline))
void Foo::bar() {}

template struct Foo;

One way to fix this would be to add _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY which is defined as attribute((visibility("default"), always_inline)).