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.
Tested on Linux x86_64.
libstdc++-v3/ChangeLog:
2022-01-07 Tom Honermann <t...@honermann.net>
* acinclude.m4 Define config macros if uchar.h provides
c8rtomb() and mbrtoc8().
* config.h.in: Re-generate.
* configure: Re-generate.
* include/c_compatibility/uchar.h: Declare ::c8rtomb and
::mbrtoc8.
* include/c_global/cuchar: Declare std::c8rtomb and
std::mbrtoc8.
* include/c_std/cuchar: Declare std::c8rtomb and std::mbrtoc8.
* testsuite/21_strings/headers/cuchar/functions_std_cxx20.cc:
New test.
* testsuite/21_strings/headers/cuchar/functions_std_fchar8_t.cc:
New test.
Tom.
[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
Tom.
commit 3d40bc9bf5c79343ea5a6cc355539542f4b56c9b
Author: Tom Honermann <t...@honermann.net>
Date: Sat Jan 1 17:26:31 2022 -0500
P0482R6 char8_t: declare std::c8rtomb and std::mbrtoc8 if provided by the C library.
This change completes implementation of the C++20 proposal P0482R6 by
adding declarations of std::c8rtomb() and std::mbrtoc8() if provided
by the C library.
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 enabled; new _GLIBCXX_USE_UCHAR_C8RTOMB_MBRTOC8_FCHAR8_T and
_GLIBCXX_USE_UCHAR_C8RTOMB_MBRTOC8_CXX20 configuration macros are defined
accordingly. 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).
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.
diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4
index 635168d7e25..85235005c7e 100644
--- a/libstdc++-v3/acinclude.m4
+++ b/libstdc++-v3/acinclude.m4
@@ -2039,6 +2039,50 @@ 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
])
diff --git a/libstdc++-v3/config.h.in b/libstdc++-v3/config.h.in
index 10675fe2530..e09744961d1 100644
--- a/libstdc++-v3/config.h.in
+++ b/libstdc++-v3/config.h.in
@@ -1000,6 +1000,14 @@
/* Define if obsolescent tmpnam is available in <stdio.h>. */
#undef _GLIBCXX_USE_TMPNAM
+/* Define if c8rtomb and std 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 c8rtomb and std functions in <uchar.h> should be
+ imported into namespace std in <cuchar> for C++20. */
+#undef _GLIBCXX_USE_UCHAR_C8RTOMB_MBRTOC8_CXX20
+
/* Define if utime is available in <utime.h>. */
#undef _GLIBCXX_USE_UTIME
diff --git a/libstdc++-v3/configure b/libstdc++-v3/configure
index b1a0157d0b9..fae78ec1cc6 100755
--- a/libstdc++-v3/configure
+++ b/libstdc++-v3/configure
@@ -19130,6 +19130,82 @@ $as_echo "#define _GLIBCXX_USE_C11_UCHAR_CXX11 1" >>confdefs.h
fi
+ CXXFLAGS="$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'
diff --git a/libstdc++-v3/include/c_compatibility/uchar.h b/libstdc++-v3/include/c_compatibility/uchar.h
index 1fe8a22f78a..b2346e70d2b 100644
--- a/libstdc++-v3/include/c_compatibility/uchar.h
+++ b/libstdc++-v3/include/c_compatibility/uchar.h
@@ -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;
diff --git a/libstdc++-v3/include/c_global/cuchar b/libstdc++-v3/include/c_global/cuchar
index 57047d74218..943d2727878 100644
--- a/libstdc++-v3/include/c_global/cuchar
+++ b/libstdc++-v3/include/c_global/cuchar
@@ -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
diff --git a/libstdc++-v3/include/c_std/cuchar b/libstdc++-v3/include/c_std/cuchar
index 7ce413e1bb0..56c11f7d24f 100644
--- a/libstdc++-v3/include/c_std/cuchar
+++ b/libstdc++-v3/include/c_std/cuchar
@@ -48,10 +48,42 @@
#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)))
+
+// 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
#undef c16rtomb
diff --git a/libstdc++-v3/testsuite/21_strings/headers/cuchar/functions_std_cxx20.cc b/libstdc++-v3/testsuite/21_strings/headers/cuchar/functions_std_cxx20.cc
new file mode 100644
index 00000000000..7c152ed42b5
--- /dev/null
+++ b/libstdc++-v3/testsuite/21_strings/headers/cuchar/functions_std_cxx20.cc
@@ -0,0 +1,12 @@
+// { dg-do compile }
+// { dg-options "-std=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
+}
diff --git a/libstdc++-v3/testsuite/21_strings/headers/cuchar/functions_std_fchar8_t.cc b/libstdc++-v3/testsuite/21_strings/headers/cuchar/functions_std_fchar8_t.cc
new file mode 100644
index 00000000000..1cfaf7427e5
--- /dev/null
+++ b/libstdc++-v3/testsuite/21_strings/headers/cuchar/functions_std_fchar8_t.cc
@@ -0,0 +1,12 @@
+// { dg-do compile }
+// { dg-options "-fchar8_t" }
+
+#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
+}
