libstdc++: Implement C++26 native handles for file streams (P1759R6)

The new __basic_file::native_handle() function can be added for C++11
and above, because the names "native_handle" and "native_handle_type"
are already reserved since C++11. Exporting those symbols from the
shared library does no harm, even if the feature gets dropped before the
C++23 standard is final.

The new member functions of std::fstream etc. are only declared for
C++26 and so are not instantiated in src/c++11/fstream-inst.cc. Declare
them with the always_inline attribute so that no symbol definitions are
needed in the library (we can change this later when C++26 support is
less experimental).

libstdc++-v3/ChangeLog:

	* acinclude.m4 (GLIBCXX_CHECK_FILEBUF_NATIVE_HANDLES): New
	macro.
	* config.h.in: Regenerate.
	* config/abi/pre/gnu.ver (GLIBCXX_3.4.32): Export new
	basic_filebuf members.
	* config/io/basic_file_stdio.cc (__basic_file::native_handle):
	Define new function.
	* config/io/basic_file_stdio.h (__basic_file::native_handle):
	Declare new function.
	* configure: Regenerate.
	* configure.ac: Use GLIBCXX_CHECK_FILEBUF_NATIVE_HANDLES.
	* include/bits/version.def (fstream_native_handles): New macro.
	* include/bits/version.h: Regenerate.
	* include/std/fstream (basic_filebuf::native_handle)
	(basic_fstream::native_handle, basic_ifstream::native_handle)
	(basic_ofstream::native_handle): New functions.
	* src/c++11/Makefile.am: Move compilation of basic_file.cc,
	locale_init.cc and localename.cc to here.
	* src/c++11/Makefile.in: Regenerate.
	* src/c++98/locale_init.cc: Moved to...
	* src/c++11/locale_init.cc: ...here.
	* src/c++98/localename.cc: Moved to...
	* src/c++11/localename.cc: ...here.
	* src/c++98/Makefile.am: Remove basic_file.cc, locale_init.cc
	and localename.cc from here.
	* src/c++98/Makefile.in: Regenerate.
	* testsuite/27_io/basic_filebuf/native_handle/version.cc: New test.
	* testsuite/27_io/basic_fstream/native_handle/char/1.cc: New test.
	* testsuite/27_io/basic_fstream/native_handle/wchar_t/1.cc: New test.
	* testsuite/27_io/basic_ifstream/native_handle/char/1.cc: New test.
	* testsuite/27_io/basic_ifstream/native_handle/wchar_t/1.cc: New test.
	* testsuite/27_io/basic_ofstream/native_handle/char/1.cc: New test.
	* testsuite/27_io/basic_ofstream/native_handle/wchar_t/1.cc: New test.

1 files changed, 57 insertions, 0 deletions

diff --git a/libstdc++-v3/configure b/libstdc++-v3/configure
index 9ac6771..13fc03b 100755
--- a/libstdc++-v3/configure
+++ b/libstdc++-v3/configure
@@ -73906,6 +73906,63 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
 
 
 
+# For __basic_file::native_handle()
+
+
+  ac_ext=cpp
+ac_cpp='$CXXCPP $CPPFLAGS'
+ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
+
+
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether _get_osfhandle is defined in <io.h>" >&5
+$as_echo_n "checking whether _get_osfhandle is defined in <io.h>... " >&6; }
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+  #if defined(_WIN32) && !defined(__CYGWIN__)
+  # include <stdint.h>
+  # include <io.h>
+  #endif
+
+int
+main ()
+{
+
+    FILE* file = 0;
+    int fd = fileno(file);
+    intptr_t crt_handle = _get_osfhandle(fd);
+    void* win32_handle = reinterpret_cast<void*>(crt_handle);
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_cxx_try_compile "$LINENO"; then :
+  ac_get_osfhandle=yes
+else
+  ac_get_osfhandle=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+  if test "$ac_objext" = yes; then
+
+cat >>confdefs.h <<_ACEOF
+#define _GLIBCXX_USE__GET_OSFHANDLE 1
+_ACEOF
+
+  fi
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_get_osfhandle" >&5
+$as_echo "$ac_get_osfhandle" >&6; }
+
+  ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+
+
 # Define documentation rules conditionally.
 
 # See if makeinfo has been installed and is modern enough