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libstdc++: Declare std::c8rtomb and std::mbrtoc8 if provided by the C library

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This patch completes implementation of the C++20 proposal P0482R6 [1] by
adding declarations of std::c8rtomb() and std::mbrtoc8() in <cuchar> if
provided by the C library in <uchar.h>.

This patch addresses feedback provided in response to a previous patch
submission [2].

Autoconf changes determine if the C library declares c8rtomb and mbrtoc8
at global scope when uchar.h is included and compiled with either
-fchar8_t or -std=c++20. New _GLIBCXX_USE_UCHAR_C8RTOMB_MBRTOC8_FCHAR8_T
and _GLIBCXX_USE_UCHAR_C8RTOMB_MBRTOC8_CXX20 configuration macros
reflect the probe results. The <cuchar> header declares these functions
in the std namespace only if available and the _GLIBCXX_USE_CHAR8_T
configuration macro is defined (by default it is defined if the C++20
__cpp_char8_t feature test macro is defined)

Patches to glibc to implement c8rtomb and mbrtoc8 have been submitted [3].

New tests validate the presence of these declarations. The tests pass
trivially if the C library does not provide these functions. Otherwise
they ensure that the functions are declared when <cuchar> is included
and either -fchar8_t or -std=c++20 is enabled.

1]: WG21 P0482R6
      "char8_t: A type for UTF-8 characters and strings (Revision 6)"
      https://wg21.link/p0482r6

[2]: [PATCH] C++ P0482R6 char8_t: declare std::c8rtomb and std::mbrtoc8
if provided by the C library
      https://gcc.gnu.org/pipermail/libstdc++/2021-June/052685.html

[3]: "C++20 P0482R6 and C2X N2653"
      [Patch 0/3]:
https://sourceware.org/pipermail/libc-alpha/2022-January/135061.html
      [Patch 1/3]:
https://sourceware.org/pipermail/libc-alpha/2022-January/135062.html
      [Patch 2/3]:
https://sourceware.org/pipermail/libc-alpha/2022-January/135063.html
      [Patch 3/3]:
https://sourceware.org/pipermail/libc-alpha/2022-January/135064.html

libstdc++-v3/ChangeLog:

	* acinclude.m4: Define config macros if uchar.h provides
	c8rtomb() and mbrtoc8().
	* config.h.in: Regenerate.
	* configure: Regenerate.
	* include/c_compatibility/uchar.h (c8rtomb, mbrtoc8): Define.
	* include/c_global/cuchar (c8rtomb, mbrtoc8): Likewise.
	* include/c_std/cuchar (c8rtomb, mbrtoc8): Likewise.
	* testsuite/21_strings/headers/cuchar/functions_std_cxx20.cc:
	New test.
	* testsuite/21_strings/headers/cuchar/functions_std_fchar8_t.cc:
	New test.
This commit is contained in:
Tom Honermann 2022-01-17 14:56:33 +00:00 • committed by Jonathan Wakely
parent d7f2a09e98
commit 0e4e4b37d9
8 changed files with 227 additions and 1 deletions
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44
libstdc++-v3/acinclude.m4
View file

@ -2044,6 +2044,50 @@ AC_DEFUN([GLIBCXX_CHECK_UCHAR_H], [
namespace std in <cuchar>.])
fi
CXXFLAGS="$CXXFLAGS -fchar8_t"
if test x"$ac_has_uchar_h" = x"yes"; then
AC_MSG_CHECKING([for c8rtomb and mbrtoc8 in <uchar.h> with -fchar8_t])
AC_TRY_COMPILE([#include <uchar.h>
namespace test
{
using ::c8rtomb;
using ::mbrtoc8;
}
],
[], [ac_uchar_c8rtomb_mbrtoc8_fchar8_t=yes],
[ac_uchar_c8rtomb_mbrtoc8_fchar8_t=no])
else
ac_uchar_c8rtomb_mbrtoc8_fchar8_t=no
fi
AC_MSG_RESULT($ac_uchar_c8rtomb_mbrtoc8_fchar8_t)
if test x"$ac_uchar_c8rtomb_mbrtoc8_fchar8_t" = x"yes"; then
AC_DEFINE(_GLIBCXX_USE_UCHAR_C8RTOMB_MBRTOC8_FCHAR8_T, 1,
[Define if c8rtomb and mbrtoc8 functions in <uchar.h> should be
imported into namespace std in <cuchar> for -fchar8_t.])
fi
CXXFLAGS="$CXXFLAGS -std=c++20"
if test x"$ac_has_uchar_h" = x"yes"; then
AC_MSG_CHECKING([for c8rtomb and mbrtoc8 in <uchar.h> with -std=c++20])
AC_TRY_COMPILE([#include <uchar.h>
namespace test
{
using ::c8rtomb;
using ::mbrtoc8;
}
],
[], [ac_uchar_c8rtomb_mbrtoc8_cxx20=yes],
[ac_uchar_c8rtomb_mbrtoc8_cxx20=no])
else
ac_uchar_c8rtomb_mbrtoc8_cxx20=no
fi
AC_MSG_RESULT($ac_uchar_c8rtomb_mbrtoc8_cxx20)
if test x"$ac_uchar_c8rtomb_mbrtoc8_cxx20" = x"yes"; then
AC_DEFINE(_GLIBCXX_USE_UCHAR_C8RTOMB_MBRTOC8_CXX20, 1,
[Define if c8rtomb and mbrtoc8 functions in <uchar.h> should be
imported into namespace std in <cuchar> for C++20.])
fi
CXXFLAGS="$ac_save_CXXFLAGS"
AC_LANG_RESTORE
])

8
libstdc++-v3/config.h.in
View file

@ -1010,6 +1010,14 @@
/* Define if obsolescent tmpnam is available in <stdio.h>. */
#undef _GLIBCXX_USE_TMPNAM
/* Define if c8rtomb and mbrtoc8 functions in <uchar.h> should be imported
into namespace std in <cuchar> for C++20. */
#undef _GLIBCXX_USE_UCHAR_C8RTOMB_MBRTOC8_CXX20
/* Define if c8rtomb and mbrtoc8 functions in <uchar.h> should be imported
into namespace std in <cuchar> for -fchar8_t. */
#undef _GLIBCXX_USE_UCHAR_C8RTOMB_MBRTOC8_FCHAR8_T
/* Define if utime is available in <utime.h>. */
#undef _GLIBCXX_USE_UTIME

76
libstdc++-v3/configure vendored
View file

@ -19151,6 +19151,82 @@ $as_echo "#define _GLIBCXX_USE_C11_UCHAR_CXX11 1" >>confdefs.h
fi
CXXFLAGS="$CXXFLAGS -fchar8_t"
if test x"$ac_has_uchar_h" = x"yes"; then
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for c8rtomb and mbrtoc8 in <uchar.h> with -fchar8_t" >&5
$as_echo_n "checking for c8rtomb and mbrtoc8 in <uchar.h> with -fchar8_t... " >&6; }
cat confdefs.h - <<_ACEOF >conftest.$ac_ext
/* end confdefs.h. */
#include <uchar.h>
namespace test
{
using ::c8rtomb;
using ::mbrtoc8;
}
int
main ()
{
;
return 0;
}
_ACEOF
if ac_fn_cxx_try_compile "$LINENO"; then :
ac_uchar_c8rtomb_mbrtoc8_fchar8_t=yes
else
ac_uchar_c8rtomb_mbrtoc8_fchar8_t=no
fi
rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
else
ac_uchar_c8rtomb_mbrtoc8_fchar8_t=no
fi
{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_uchar_c8rtomb_mbrtoc8_fchar8_t" >&5
$as_echo "$ac_uchar_c8rtomb_mbrtoc8_fchar8_t" >&6; }
if test x"$ac_uchar_c8rtomb_mbrtoc8_fchar8_t" = x"yes"; then
$as_echo "#define _GLIBCXX_USE_UCHAR_C8RTOMB_MBRTOC8_FCHAR8_T 1" >>confdefs.h
fi
CXXFLAGS="$CXXFLAGS -std=c++20"
if test x"$ac_has_uchar_h" = x"yes"; then
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for c8rtomb and mbrtoc8 in <uchar.h> with -std=c++20" >&5
$as_echo_n "checking for c8rtomb and mbrtoc8 in <uchar.h> with -std=c++20... " >&6; }
cat confdefs.h - <<_ACEOF >conftest.$ac_ext
/* end confdefs.h. */
#include <uchar.h>
namespace test
{
using ::c8rtomb;
using ::mbrtoc8;
}
int
main ()
{
;
return 0;
}
_ACEOF
if ac_fn_cxx_try_compile "$LINENO"; then :
ac_uchar_c8rtomb_mbrtoc8_cxx20=yes
else
ac_uchar_c8rtomb_mbrtoc8_cxx20=no
fi
rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
else
ac_uchar_c8rtomb_mbrtoc8_cxx20=no
fi
{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_uchar_c8rtomb_mbrtoc8_cxx20" >&5
$as_echo "$ac_uchar_c8rtomb_mbrtoc8_cxx20" >&6; }
if test x"$ac_uchar_c8rtomb_mbrtoc8_cxx20" = x"yes"; then
$as_echo "#define _GLIBCXX_USE_UCHAR_C8RTOMB_MBRTOC8_CXX20 1" >>confdefs.h
fi
CXXFLAGS="$ac_save_CXXFLAGS"
ac_ext=c
ac_cpp='$CPP $CPPFLAGS'

8
libstdc++-v3/include/c_compatibility/uchar.h
View file

@ -33,6 +33,14 @@
#ifdef _GLIBCXX_NAMESPACE_C
#if (_GLIBCXX_USE_CHAR8_T \
&& (_GLIBCXX_USE_UCHAR_C8RTOMB_MBRTOC8_FCHAR8_T \
|| (__cplusplus >= 202002 \
&& _GLIBCXX_USE_UCHAR_C8RTOMB_MBRTOC8_CXX20)))
using std::mbrtoc8;
using std::c8rtomb;
#endif // _GLIBCXX_USE_CHAR8_T
#if _GLIBCXX_USE_C11_UCHAR_CXX11
using std::mbrtoc16;
using std::c16rtomb;

33
libstdc++-v3/include/c_global/cuchar
View file

@ -48,10 +48,41 @@
#include <bits/c++config.h>
#include <cwchar>
#if _GLIBCXX_USE_C11_UCHAR_CXX11
#if (_GLIBCXX_USE_C11_UCHAR_CXX11 \
|| (_GLIBCXX_USE_CHAR8_T \
&& (_GLIBCXX_USE_UCHAR_C8RTOMB_MBRTOC8_FCHAR8_T \
|| (__cplusplus >= 202002 \
&& _GLIBCXX_USE_UCHAR_C8RTOMB_MBRTOC8_CXX20))))
#include <uchar.h>
#endif
// Support for mbrtoc8 and c8rtomb is conditioned on support by the C library.
#if (_GLIBCXX_USE_CHAR8_T \
&& (_GLIBCXX_USE_UCHAR_C8RTOMB_MBRTOC8_FCHAR8_T \
|| (__cplusplus >= 202002 \
&& _GLIBCXX_USE_UCHAR_C8RTOMB_MBRTOC8_CXX20)))
#undef mbrtoc8
#undef c8rtomb
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
using ::mbrtoc8;
using ::c8rtomb;
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std
#endif // _GLIBCXX_USE_CHAR8_T
#if _GLIBCXX_USE_C11_UCHAR_CXX11
// Get rid of those macros defined in <uchar.h> in lieu of real functions.
#undef mbrtoc16
#undef c16rtomb

35
libstdc++-v3/include/c_std/cuchar
View file

@ -50,7 +50,42 @@
#if _GLIBCXX_USE_C11_UCHAR_CXX11
#if (_GLIBCXX_USE_C11_UCHAR_CXX11 \
|| (_GLIBCXX_USE_CHAR8_T \
&& (_GLIBCXX_USE_UCHAR_C8RTOMB_MBRTOC8_FCHAR8_T \
|| (__cplusplus >= 202002 \
&& _GLIBCXX_USE_UCHAR_C8RTOMB_MBRTOC8_CXX20))))
#include <uchar.h>
#endif
// Support for mbrtoc8 and c8rtomb is conditioned on support by the C library.
#if (_GLIBCXX_USE_CHAR8_T \
&& (_GLIBCXX_USE_UCHAR_C8RTOMB_MBRTOC8_FCHAR8_T \
|| (__cplusplus >= 202002 \
&& _GLIBCXX_USE_UCHAR_C8RTOMB_MBRTOC8_CXX20)))
// Get rid of those macros defined in <uchar.h> in lieu of real functions.
#undef mbrtoc8
#undef c8rtomb
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
using ::mbrtoc8;
using ::c8rtomb;
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std
#endif // _GLIBCXX_USE_CHAR8_T
#if _GLIBCXX_USE_C11_UCHAR_CXX11
// Get rid of those macros defined in <uchar.h> in lieu of real functions.
#undef mbrtoc16

12
libstdc++-v3/testsuite/21_strings/headers/cuchar/functions_std_cxx20.cc Normal file
View file

@ -0,0 +1,12 @@
// { dg-options "-std=c++20" }
// { dg-do compile { target c++20 } }
#include <cuchar>
namespace gnu
{
#if _GLIBCXX_USE_UCHAR_C8RTOMB_MBRTOC8_CXX20
using std::mbrtoc8;
using std::c8rtomb;
#endif // _GLIBCXX_USE_UCHAR_C8RTOMB_MBRTOC8_CXX20
}

12
libstdc++-v3/testsuite/21_strings/headers/cuchar/functions_std_fchar8_t.cc Normal file
View file

@ -0,0 +1,12 @@
// { dg-options "-fchar8_t" }
// { dg-do compile { target c++11 } }
#include <cuchar>
namespace gnu
{
#if _GLIBCXX_USE_UCHAR_C8RTOMB_MBRTOC8_FCHAR8_T
using std::mbrtoc8;
using std::c8rtomb;
#endif // _GLIBCXX_USE_UCHAR_C8RTOMB_MBRTOC8_FCHAR8_T
}