libstdc++: Fix std::filesystem errors with -fkeep-inline-functions [PR108636]

With -fkeep-inline-functions there are linker errors when including
<filesystem>. This happens because there are some filesystem::path
constructors defined inline which call non-exported functions defined in
the library. That's usually not a problem, because those constructors
are only called by code that's also inside the library. But when the
header is compiled with -fkeep-inline-functions those inline functions
are emitted even though they aren't called. That then creates an
undefined reference to the other library internsl. The fix is to just
move the private constructors into the library where they are called.
That way they are never even seen by users, and so not compiled even if
-fkeep-inline-functions is used.

On trunk there is a second problem, which is that the new equality
operators for comparing directory iterators with default_sentinel use
the shared_ptr::operator bool() conversion operator. The shared_ptr
specializations used by directory iterators are explicitly instantiated
in the library, but the bool conversion operators are not exported. This
causes linker errors at -O0 or with -fkeep-inline-functions. That just
requires the conversion operators to be exported.

libstdc++-v3/ChangeLog:

	PR libstdc++/108636
	* config/abi/pre/gnu.ver (GLIBCXX_3.4.31): Export shared_ptr
	conversion operators for directory iterator comparisons with
	std::default_sentinel_t.
	* include/bits/fs_path.h (path::path(string_view, _Type))
	(path::_Cmpt::_Cmpt(string_view, _Type, size_t)): Move inline
	definitions to ...
	* src/c++17/fs_path.cc: ... here.
	* testsuite/27_io/filesystem/path/108636.cc: New test.

4 files changed, 30 insertions, 8 deletions

diff --git a/libstdc++-v3/config/abi/pre/gnu.ver b/libstdc++-v3/config/abi/pre/gnu.ver
index 7271641..34f23bc 100644
--- a/libstdc++-v3/config/abi/pre/gnu.ver
+++ b/libstdc++-v3/config/abi/pre/gnu.ver
@@ -2504,6 +2504,13 @@ GLIBCXX_3.4.31 {
     _ZNSt6chrono9tzdb_list14const_iteratorppEi;
     _ZN9__gnu_cxx21zoneinfo_dir_overrideEv;
 
+    # __shared_ptr<directory_iterator::_Dir>::operator bool()
+    _ZNKSt12__shared_ptrINSt10filesystem4_DirELN9__gnu_cxx12_Lock_policyE[012]EEcvbEv;
+    _ZNKSt12__shared_ptrINSt10filesystem7__cxx114_DirELN9__gnu_cxx12_Lock_policyE[012]EEcvbEv;
+    # __shared_ptr<recursive_directory_iterator::_Dir_stack>::operator bool()
+    _ZNKSt12__shared_ptrINSt10filesystem28recursive_directory_iterator10_Dir_stackELN9__gnu_cxx12_Lock_policyE[012]EEcvbEv;
+    _ZNKSt12__shared_ptrINSt10filesystem7__cxx1128recursive_directory_iterator10_Dir_stackELN9__gnu_cxx12_Lock_policyE[012]EEcvbEv;
+
 } GLIBCXX_3.4.30;
 
 # Symbols in the support library (libsupc++) have their own tag.
diff --git a/libstdc++-v3/include/bits/fs_path.h b/libstdc++-v3/include/bits/fs_path.h
index 1cbfaaa..0d7bb10 100644
--- a/libstdc++-v3/include/bits/fs_path.h
+++ b/libstdc++-v3/include/bits/fs_path.h
@@ -596,12 +596,7 @@ namespace __detail
       _Multi = 0, _Root_name, _Root_dir, _Filename
     };
 
-    path(basic_string_view<value_type> __str, _Type __type)
-    : _M_pathname(__str)
-    {
-      __glibcxx_assert(__type != _Type::_Multi);
-      _M_cmpts.type(__type);
-    }
+    path(basic_string_view<value_type> __str, _Type __type);
 
     enum class _Split { _Stem, _Extension };
 
@@ -851,8 +846,7 @@ namespace __detail
 
   struct path::_Cmpt : path
   {
-    _Cmpt(basic_string_view<value_type> __s, _Type __t, size_t __pos)
-      : path(__s, __t), _M_pos(__pos) { }
+    _Cmpt(basic_string_view<value_type> __s, _Type __t, size_t __pos);
 
     _Cmpt() : _M_pos(-1) { }
 
diff --git a/libstdc++-v3/src/c++17/fs_path.cc b/libstdc++-v3/src/c++17/fs_path.cc
index 93149c4..aaea7d2 100644
--- a/libstdc++-v3/src/c++17/fs_path.cc
+++ b/libstdc++-v3/src/c++17/fs_path.cc
@@ -187,6 +187,19 @@ struct path::_Parser
   { return origin + c.str.data() - input.data(); }
 };
 
+inline
+path::path(basic_string_view<value_type> __str, _Type __type)
+: _M_pathname(__str)
+{
+  __glibcxx_assert(__type != _Type::_Multi);
+  _M_cmpts.type(__type);
+}
+
+inline
+path::_Cmpt::_Cmpt(basic_string_view<value_type> __s, _Type __t, size_t __pos)
+: path(__s, __t), _M_pos(__pos)
+{ }
+
 struct path::_List::_Impl
 {
   using value_type = _Cmpt;
diff --git a/libstdc++-v3/testsuite/27_io/filesystem/path/108636.cc b/libstdc++-v3/testsuite/27_io/filesystem/path/108636.cc
new file mode 100644
index 0000000..d58de46
--- /dev/null
+++ b/libstdc++-v3/testsuite/27_io/filesystem/path/108636.cc
@@ -0,0 +1,8 @@
+// { dg-do link { target c++17 } }
+// { dg-options "-fkeep-inline-functions" }
+
+#include <filesystem>
+int main()
+{
+  // PR libstdc++/108636 - link failure with -fkeep-inline-functions
+}