[Bug libstdc++/64203] New: shared_mutex compile errors on bare-metal targets

["sandra at codesourcery dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64203

            Bug ID: 64203
           Summary: shared_mutex compile errors on bare-metal targets
           Product: gcc
           Version: 4.9.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: sandra at codesourcery dot com
                CC: 3dw4rd at verizon dot net

After merging GCC 4.9.2 onto our local branch, I saw that the new libstdc++
testcase experimental/feat-cxx14.cc is failing on bare-metal targets
(arm-none-eabi, mips-sde-elf, powerpc-eabi, possibly others).  Here's an
excerpt from the test logs:

Executing on host: mips-sde-elf-g++ -fdiagnostics-color=never -D_GLIBCXX_ASSERT
-fmessage-length=0  -g -O2 -DLOCALEDIR="."
-I/scratch/sandra/mips-elf-trunk/src/gcc-trunk-4.9/libstdc++-v3/testsuite/util
/scratch/sandra/mips-elf-trunk/src/gcc-trunk-4.9/libstdc++-v3/testsuite/experimental/feat-cxx14.cc
  -std=gnu++14 -S    -mips16 -o feat-cxx14.s    (timeout = 600)
/scratch/sandra/mips-elf-trunk/src/gcc-trunk-4.9/libstdc++-v3/testsuite/experimental/feat-cxx14.cc:110:4:
error: #error "__cpp_lib_shared_timed_mutex"
 #  error "__cpp_lib_shared_timed_mutex"
    ^
In file included from
/scratch/sandra/mips-elf-trunk/src/gcc-trunk-4.9/libstdc++-v3/testsuite/experimental/feat-cxx14.cc:13:0:
/scratch/sandra/mips-elf-trunk/install/opt/codesourcery/mips-sde-elf/include/c++/4.9.2/shared_mutex:274:36:
error: 'defer_lock_t' has not been declared
       shared_lock(mutex_type& __m, defer_lock_t) noexcept
                                    ^
/scratch/sandra/mips-elf-trunk/install/opt/codesourcery/mips-sde-elf/include/c++/4.9.2/shared_mutex:277:36:
error: 'try_to_lock_t' has not been declared
       shared_lock(mutex_type& __m, try_to_lock_t)
                                    ^
/scratch/sandra/mips-elf-trunk/install/opt/codesourcery/mips-sde-elf/include/c++/4.9.2/shared_mutex:277:7:
error:
'std::shared_lock<_Mutex>::shared_lock(std::shared_lock<_Mutex>::mutex_type&,
int)' cannot be overloaded
       shared_lock(mutex_type& __m, try_to_lock_t)
       ^
/scratch/sandra/mips-elf-trunk/install/opt/codesourcery/mips-sde-elf/include/c++/4.9.2/shared_mutex:274:7:
error: with
'std::shared_lock<_Mutex>::shared_lock(std::shared_lock<_Mutex>::mutex_type&,
int)'
       shared_lock(mutex_type& __m, defer_lock_t) noexcept
       ^
/scratch/sandra/mips-elf-trunk/install/opt/codesourcery/mips-sde-elf/include/c++/4.9.2/shared_mutex:280:36:
error: 'adopt_lock_t' has not been declared
       shared_lock(mutex_type& __m, adopt_lock_t)
                                    ^
/scratch/sandra/mips-elf-trunk/install/opt/codesourcery/mips-sde-elf/include/c++/4.9.2/shared_mutex:280:7:
error:
'std::shared_lock<_Mutex>::shared_lock(std::shared_lock<_Mutex>::mutex_type&,
int)' cannot be overloaded
       shared_lock(mutex_type& __m, adopt_lock_t)
       ^
/scratch/sandra/mips-elf-trunk/install/opt/codesourcery/mips-sde-elf/include/c++/4.9.2/shared_mutex:274:7:
error: with
'std::shared_lock<_Mutex>::shared_lock(std::shared_lock<_Mutex>::mutex_type&,
int)'
       shared_lock(mutex_type& __m, defer_lock_t) noexcept
       ^
/scratch/sandra/mips-elf-trunk/install/opt/codesourcery/mips-sde-elf/include/c++/4.9.2/shared_mutex:
In member function 'void std::shared_lock<_Mutex>::unlock()':
/scratch/sandra/mips-elf-trunk/install/opt/codesourcery/mips-sde-elf/include/c++/4.9.2/shared_mutex:347:29:
error: 'errc' was not declared in this scope
    __throw_system_error(int(errc::resource_deadlock_would_occur));
                             ^
/scratch/sandra/mips-elf-trunk/install/opt/codesourcery/mips-sde-elf/include/c++/4.9.2/shared_mutex:
In member function 'void std::shared_lock<_Mutex>::_M_lockable() const':
/scratch/sandra/mips-elf-trunk/install/opt/codesourcery/mips-sde-elf/include/c++/4.9.2/shared_mutex:381:29:
error: 'errc' was not declared in this scope
    __throw_system_error(int(errc::operation_not_permitted));
                             ^
/scratch/sandra/mips-elf-trunk/install/opt/codesourcery/mips-sde-elf/include/c++/4.9.2/shared_mutex:383:29:
error: 'errc' was not declared in this scope
    __throw_system_error(int(errc::resource_deadlock_would_occur));
                             ^
compiler exited with status 1

I am guessing this part of <shared_mutex> is to blame:

#if defined(_GLIBCXX_HAS_GTHREADS) && defined(_GLIBCXX_USE_C99_STDINT_TR1)
# include <mutex>
# include <condition_variable>
#endif

Because of the guards, I think <mutex> is not being included and nothing else
is providing declarations of the missing identifiers.  I don't know my way
around this code or the C++ library specification at all, though.