Bug 1395185

Description of problem:
Template functions with the always_inline attribute cannot be called from non-inline functions in a precompiled header without causing compilation of the precompiled header to fail.

Version-Release number of selected component (if applicable):
Arch: x86_64
Version: GCC 6.2.1
Release: 2.fc24

How reproducible:
Occurs every time.

Steps to Reproduce:
Compile the following code with g++ -x c++-header [filename]:
template <typename T> __attribute__((always_inline)) inline void f() {}
void g() {f<float>();}

Actual results:
$ g++ -x c++-header precompiled_header_bug.hh
precompiled_header_bug.hh: In function ‘void g()’:
precompiled_header_bug.hh:1:66: error: inlining failed in call to always_inline ‘void f() [with T = float]’: function body not available
 template <typename T> __attribute__((always_inline)) inline void f() {}
                                                                  ^
precompiled_header_bug.hh:2:21: note: called from here
 void g() {f<float>();}
                     ^
Expected results:
The compile should succeed. At least, if there is an error, it should not say "function body not available" and point to the function definition (as it has the function body right there).

Additional info:
The same code compiles successfully if compiled with -x c++ -c, and function f is inlined into g in this case.
It would also compile successfully if function g was declared inline. Normally, you wouldn't expect non-inline functions in a precompiled header, as using the precompiled header on multiple translation unit would create multiple symbol definitions. I found code which was using __attribute__((noinline)) __attribute__((weak)) on a function in a precompiled however. That function called an always_inline function, which called a templated always_inline function. The error message for that case does not refer to the original noinline weak function which was required to produce the error.