ISO C 23 specifies a new type, to be defined by <uchar.h>.
This patch adds it.
2023-03-27 Bruno Haible <br...@clisp.org>
uchar: ISO C 23: Define char8_t.
* lib/uchar.in.h (char8_t): New type or macro.
* m4/uchar_h.m4 (gl_TYPE_CHAR8_T): New macro.
(gl_UCHAR_H): Invoke it. Set CXX_HAS_CHAR8_TYPE.
* modules/uchar (Makefile.am): Substitute CXX_HAS_CHAR8_TYPE,
GNULIBHEADERS_OVERRIDE_CHAR8_T.
* tests/test-uchar.c: Add tests for char8_t.
diff --git a/lib/uchar.in.h b/lib/uchar.in.h
index 115ae1e84b..4d5f07fcce 100644
--- a/lib/uchar.in.h
+++ b/lib/uchar.in.h
@@ -17,7 +17,7 @@
/* Written by Bruno Haible <br...@clisp.org>, 2019. */
/*
- * ISO C 11 <uchar.h> for platforms that lack it.
+ * ISO C 23 <uchar.h> for platforms that lack it.
*/
#ifndef _@GUARD_PREFIX@_UCHAR_H
@@ -58,11 +58,26 @@
/* The definitions of _GL_FUNCDECL_RPL etc. are copied here. */
+#if !(@HAVE_UCHAR_H@ || (defined __cplusplus && @CXX_HAS_CHAR8_TYPE@))
+
+/* An 8-bit variant of wchar_t.
+ Note: This type is only mandated by ISO C 23 or newer, and it does
+ denote UTF-8 units. */
+typedef unsigned char char8_t;
+
+#elif @GNULIBHEADERS_OVERRIDE_CHAR8_T@
+
+typedef unsigned char gl_char8_t;
+# define char8_t gl_char8_t
+
+#endif
+
#if !(@HAVE_UCHAR_H@ || (defined __cplusplus && @CXX_HAS_UCHAR_TYPES@))
/* A 16-bit variant of wchar_t.
- Note: This type does *NOT* denote UTF-16 units. (Only on platforms
- on which __STDC_UTF_16__ is defined.) */
+ Note: This type is only mandated by ISO C 11 or newer. In ISO C 23
+ and newer, it denotes UTF-16 units; in older versions of ISO C it did
+ so only on platforms on which __STDC_UTF_16__ was defined. */
typedef uint_least16_t char16_t;
#elif @GNULIBHEADERS_OVERRIDE_CHAR16_T@
@@ -75,8 +90,9 @@ typedef uint_least16_t gl_char16_t;
#if !(@HAVE_UCHAR_H@ || (defined __cplusplus && @CXX_HAS_UCHAR_TYPES@))
/* A 32-bit variant of wchar_t.
- Note: This type does *NOT* denote UTF-32 code points. (Only on platforms
- on which __STDC_UTF_32__ is defined.) */
+ Note: This type is only mandated by ISO C 11 or newer. In ISO C 23
+ and newer, it denotes UTF-32 code points; in older versions of ISO C
+ it did so only on platforms on which __STDC_UTF_32__ was defined. */
typedef uint_least32_t char32_t;
#elif @GNULIBHEADERS_OVERRIDE_CHAR32_T@
diff --git a/m4/uchar_h.m4 b/m4/uchar_h.m4
index 2d1869a293..6df3056b32 100644
--- a/m4/uchar_h.m4
+++ b/m4/uchar_h.m4
@@ -1,4 +1,4 @@
-# uchar_h.m4 serial 20
+# uchar_h.m4 serial 21
dnl Copyright (C) 2019-2023 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
@@ -19,6 +19,7 @@ AC_DEFUN_ONCE([gl_UCHAR_H]
fi
AC_SUBST([HAVE_UCHAR_H])
+ gl_TYPE_CHAR8_T
gl_TYPE_CHAR16_T
gl_TYPE_CHAR32_T
@@ -26,6 +27,7 @@ AC_DEFUN_ONCE([gl_UCHAR_H]
dnl on some platforms (e.g. OpenBSD 6.7), and as types defined by many
dnl header files (<limits.h>, <stddef.h>, <stdint.h>, <stdio.h>, <stdlib.h>
dnl and others) on some platforms (e.g. Mac OS X 10.13).
+ dnl The same thing may also happen for 'char8_t'; so, be prepared for it.
m4_ifdef([gl_ANSI_CXX], [AC_REQUIRE([gl_ANSI_CXX])])
CXX_HAS_UCHAR_TYPES=0
if test $HAVE_UCHAR_H = 0; then
@@ -53,6 +55,31 @@ AC_DEFUN_ONCE([gl_UCHAR_H]
fi
fi
AC_SUBST([CXX_HAS_UCHAR_TYPES])
+ CXX_HAS_CHAR8_TYPE=0
+ if test $HAVE_UCHAR_H = 0; then
+ if test "$CXX" != no; then
+ AC_CACHE_CHECK([whether the C++ compiler predefines the char8_t types],
+ [gl_cv_cxx_has_char8_type],
+ [dnl We can't use AC_LANG_PUSH([C++]) and AC_LANG_POP([C++]) here, due
to
+ dnl an autoconf bug <https://savannah.gnu.org/support/?110294>.
+ cat > conftest.cpp <<\EOF
+#include <stddef.h>
+char8_t a;
+EOF
+ gl_command="$CXX $CXXFLAGS $CPPFLAGS -c conftest.cpp"
+ if AC_TRY_EVAL([gl_command]); then
+ gl_cv_cxx_has_char8_type=yes
+ else
+ gl_cv_cxx_has_char8_type=no
+ fi
+ rm -fr conftest*
+ ])
+ if test $gl_cv_cxx_has_char8_type = yes; then
+ CXX_HAS_CHAR8_TYPE=1
+ fi
+ fi
+ fi
+ AC_SUBST([CXX_HAS_CHAR8_TYPE])
dnl Test whether a 'char32_t' can hold more characters than a 'wchar_t'.
gl_STDINT_BITSIZEOF([wchar_t], [gl_STDINT_INCLUDES])
@@ -71,6 +98,28 @@ AC_DEFUN_ONCE([gl_UCHAR_H]
]], [c32rtomb mbrtoc32])
])
+AC_DEFUN_ONCE([gl_TYPE_CHAR8_T],
+[
+ dnl Determine whether gnulib's <uchar.h> would, if present, override char8_t.
+ AC_CACHE_CHECK([whether char8_t is correctly defined],
+ [gl_cv_type_char8_t_works],
+ [AC_COMPILE_IFELSE(
+ [AC_LANG_PROGRAM([[
+ #include <uchar.h>
+ int verify[(char8_t)(-1) >= 0 && sizeof (char8_t) == sizeof
(unsigned char) ? 1 : -1];
+ ]])
+ ],
+ [gl_cv_type_char8_t_works=yes],
+ [gl_cv_type_char8_t_works=no])
+ ])
+ if test $gl_cv_type_char8_t_works = no; then
+ GNULIBHEADERS_OVERRIDE_CHAR8_T=1
+ else
+ GNULIBHEADERS_OVERRIDE_CHAR8_T=0
+ fi
+ AC_SUBST([GNULIBHEADERS_OVERRIDE_CHAR8_T])
+])
+
dnl On Haiku 2020, char16_t and char32_t are incorrectly defined.
dnl See <https://dev.haiku-os.org/ticket/15990>.
AC_DEFUN_ONCE([gl_TYPE_CHAR16_T],
diff --git a/modules/uchar b/modules/uchar
index 2c947ed243..8cf4cfb5cf 100644
--- a/modules/uchar
+++ b/modules/uchar
@@ -30,8 +30,10 @@ uchar.h: uchar.in.h $(top_builddir)/config.status
$(CXXDEFS_H)
-e 's|@''PRAGMA_SYSTEM_HEADER''@|@PRAGMA_SYSTEM_HEADER@|g' \
-e 's|@''PRAGMA_COLUMNS''@|@PRAGMA_COLUMNS@|g' \
-e 's|@''NEXT_UCHAR_H''@|$(NEXT_UCHAR_H)|g' \
+ -e 's|@''CXX_HAS_CHAR8_TYPE''@|$(CXX_HAS_CHAR8_TYPE)|g' \
-e 's|@''CXX_HAS_UCHAR_TYPES''@|$(CXX_HAS_UCHAR_TYPES)|g' \
-e 's|@''SMALL_WCHAR_T''@|$(SMALL_WCHAR_T)|g' \
+ -e
's|@''GNULIBHEADERS_OVERRIDE_CHAR8_T''@|$(GNULIBHEADERS_OVERRIDE_CHAR8_T)|g' \
-e
's|@''GNULIBHEADERS_OVERRIDE_CHAR16_T''@|$(GNULIBHEADERS_OVERRIDE_CHAR16_T)|g' \
-e
's|@''GNULIBHEADERS_OVERRIDE_CHAR32_T''@|$(GNULIBHEADERS_OVERRIDE_CHAR32_T)|g' \
-e 's/@''GNULIB_BTOC32''@/$(GNULIB_BTOC32)/g' \
diff --git a/tests/test-uchar.c b/tests/test-uchar.c
index 0d5b7d77eb..38c5f2538e 100644
--- a/tests/test-uchar.c
+++ b/tests/test-uchar.c
@@ -23,15 +23,23 @@
/* Check that the types are defined. */
mbstate_t a = { 0 };
size_t b = 5;
-char16_t c = 'x';
-char32_t d = 'y';
+char8_t c = 'x';
+char16_t d = 'y';
+char32_t e = 'z';
-/* Check that char16_t and char32_t are unsigned types. */
+/* Check that char8_t, char16_t, and char32_t are unsigned types. */
+static_assert ((char8_t)(-1) >= 0);
static_assert ((char16_t)(-1) >= 0);
#if !defined __HP_cc
static_assert ((char32_t)(-1) >= 0);
#endif
+/* Check that char8_t is at least 8 bits wide. */
+static_assert ((char8_t)0xFF != (char8_t)0x7F);
+
+/* Check that char16_t is at least 16 bits wide. */
+static_assert ((char16_t)0xFFFF != (char16_t)0x7FFF);
+
/* Check that char32_t is at least 31 bits wide. */
static_assert ((char32_t)0x7FFFFFFF != (char32_t)0x3FFFFFFF);
