uchar: Work around incorrect char16_t, char32_t types on Haiku 2020

[Bruno Haible]

On a recent Haiku/x86_64, a gnulib testdir fails to compile:

In file included from ../../gltests/test-uchar.c:23:
../../gltests/../gllib/verify.h:216:41: error: static assertion failed: "verify 
((char16_t)(-1) >= 0)"
 # define _GL_VERIFY(R, DIAGNOSTIC, ...) _Static_assert (R, DIAGNOSTIC)
                                         ^~~~~~~~~~~~~~
../../gltests/../gllib/verify.h:276:20: note: in expansion of macro '_GL_VERIFY'
 # define verify(R) _GL_VERIFY (R, "verify (" #R ")", -)
                    ^~~~~~~~~~
../../gltests/test-uchar.c:32:1: note: in expansion of macro 'verify'
 verify ((char16_t)(-1) >= 0);
 ^~~~~~
../../gltests/../gllib/verify.h:216:41: error: static assertion failed: "verify 
((char32_t)(-1) >= 0)"
 # define _GL_VERIFY(R, DIAGNOSTIC, ...) _Static_assert (R, DIAGNOSTIC)
                                         ^~~~~~~~~~~~~~
../../gltests/../gllib/verify.h:276:20: note: in expansion of macro '_GL_VERIFY'
 # define verify(R) _GL_VERIFY (R, "verify (" #R ")", -)
                    ^~~~~~~~~~
../../gltests/test-uchar.c:34:1: note: in expansion of macro 'verify'
 verify ((char32_t)(-1) >= 0);
 ^~~~~~

The reason is that the char16_t and char32_t types are incorrectly defined.
Reported at <https://dev.haiku-os.org/ticket/15990>. But since the bug exists
already for two years and is fatal, let me add a workaround.


2020-05-09  Bruno Haible  <address@hidden>

        uchar: Work around incorrect char16_t, char32_t types on Haiku 2020.
        * lib/uchar.in.h (char16_t): Define as macro if
        GNULIB_OVERRIDES_CHAR16_T.
        (char32_t): Define as macro if GNULIB_OVERRIDES_CHAR32_T.
        * m4/uchar.m4 (gl_TYPE_CHAR16_T, gl_TYPE_CHAR32_T): New macros.
        (gl_UCHAR_H): Invoke them.
        (gl_UCHAR_H_DEFAULTS): Initialize GNULIB_OVERRIDES_CHAR16_T,
        GNULIB_OVERRIDES_CHAR32_T.
        * m4/mbrtoc32.m4 (gl_FUNC_MBRTOC32, gl_MBRTOC32_SANITYCHECK): Require
        gl_TYPE_CHAR32_T and test GNULIB_OVERRIDES_CHAR32_T.
        * modules/uchar (Makefile.am): Substitute GNULIB_OVERRIDES_CHAR16_T,
        GNULIB_OVERRIDES_CHAR32_T.

diff --git a/lib/uchar.in.h b/lib/uchar.in.h
index 9c76cc9..b77116d 100644
--- a/lib/uchar.in.h
+++ b/lib/uchar.in.h
@@ -47,11 +47,25 @@
    on which __STDC_UTF_16__ is defined.)  */
 typedef uint_least16_t char16_t;
 
+#elif @GNULIB_OVERRIDES_CHAR16_T@
+
+typedef uint_least16_t gl_char16_t;
+# define char16_t gl_char16_t
+
+#endif
+
+#if !@HAVE_UCHAR_H@
+
 /* 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.)  */
 typedef uint_least32_t char32_t;
 
+#elif @GNULIB_OVERRIDES_CHAR32_T@
+
+typedef uint_least32_t gl_char32_t;
+# define char32_t gl_char32_t
+
 #endif
 
 /* Define if a 'char32_t' can hold more characters than a 'wchar_t'.  */
diff --git a/m4/mbrtoc32.m4 b/m4/mbrtoc32.m4
index 991bbc8..5b5e938 100644
--- a/m4/mbrtoc32.m4
+++ b/m4/mbrtoc32.m4
@@ -1,4 +1,4 @@
-# mbrtoc32.m4 serial 4
+# mbrtoc32.m4 serial 5
 dnl Copyright (C) 2014-2020 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -11,13 +11,14 @@ AC_DEFUN([gl_FUNC_MBRTOC32],
   AC_REQUIRE([AC_TYPE_MBSTATE_T])
   gl_MBSTATE_T_BROKEN
 
+  AC_REQUIRE([gl_TYPE_CHAR32_T])
   AC_REQUIRE([gl_MBRTOC32_SANITYCHECK])
 
   AC_REQUIRE([gl_CHECK_FUNC_MBRTOC32])
   if test $gl_cv_func_mbrtoc32 = no; then
     HAVE_MBRTOC32=0
   else
-    if test $REPLACE_MBSTATE_T = 1; then
+    if test $GNULIB_OVERRIDES_CHAR32_T = 1 || test $REPLACE_MBSTATE_T = 1; then
       REPLACE_MBRTOC32=1
     else
       gl_MBRTOC32_EMPTY_INPUT
@@ -141,11 +142,12 @@ dnl Result is HAVE_WORKING_MBRTOC32.
 AC_DEFUN([gl_MBRTOC32_SANITYCHECK],
 [
   AC_REQUIRE([AC_PROG_CC])
+  AC_REQUIRE([gl_TYPE_CHAR32_T])
   AC_REQUIRE([gl_CHECK_FUNC_MBRTOC32])
   AC_REQUIRE([gt_LOCALE_FR])
   AC_REQUIRE([gt_LOCALE_ZH_CN])
   AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
-  if test $gl_cv_func_mbrtoc32 = no; then
+  if test $GNULIB_OVERRIDES_CHAR32_T = 1 || test $gl_cv_func_mbrtoc32 = no; 
then
     HAVE_WORKING_MBRTOC32=0
   else
     AC_CACHE_CHECK([whether mbrtoc32 works as well as mbrtowc],
diff --git a/m4/uchar.m4 b/m4/uchar.m4
index 63d8b13..0875caa 100644
--- a/m4/uchar.m4
+++ b/m4/uchar.m4
@@ -1,4 +1,4 @@
-# uchar.m4 serial 13
+# uchar.m4 serial 14
 dnl Copyright (C) 2019-2020 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 +19,9 @@ AC_DEFUN_ONCE([gl_UCHAR_H],
   fi
   AC_SUBST([HAVE_UCHAR_H])
 
+  gl_TYPE_CHAR16_T
+  gl_TYPE_CHAR32_T
+
   dnl Test whether a 'char32_t' can hold more characters than a 'wchar_t'.
   gl_STDINT_BITSIZEOF([wchar_t], [gl_STDINT_INCLUDES])
   if test $BITSIZEOF_WCHAR_T -lt 32; then
@@ -36,6 +39,51 @@ AC_DEFUN_ONCE([gl_UCHAR_H],
     ]], [c32rtomb mbrtoc32])
 ])
 
+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],
+[
+  AC_REQUIRE([gl_UCHAR_H_DEFAULTS])
+  dnl Determine whether gnulib's <uchar.h> would, if present, override 
char16_t.
+  AC_CACHE_CHECK([whether char16_t is correctly defined],
+    [gl_cv_type_char16_t_works],
+    [AC_COMPILE_IFELSE(
+       [AC_LANG_PROGRAM([[
+          #include <uchar.h>
+          /* For simplicity, assume that uint16_least_t is equivalent to
+             'unsigned short'.  */
+          int verify[(char16_t)(-1) >= 0 && sizeof (char16_t) == sizeof 
(unsigned short) ? 1 : -1];
+          ]])
+       ],
+       [gl_cv_type_char16_t_works=yes],
+       [gl_cv_type_char16_t_works=no])
+    ])
+  if test $gl_cv_type_char16_t_works = no; then
+    GNULIB_OVERRIDES_CHAR16_T=1
+  fi
+])
+AC_DEFUN_ONCE([gl_TYPE_CHAR32_T],
+[
+  AC_REQUIRE([gl_UCHAR_H_DEFAULTS])
+  dnl Determine whether gnulib's <uchar.h> would, if present, override 
char32_t.
+  AC_CACHE_CHECK([whether char32_t is correctly defined],
+    [gl_cv_type_char32_t_works],
+    [AC_COMPILE_IFELSE(
+       [AC_LANG_PROGRAM([[
+          #include <uchar.h>
+          /* For simplicity, assume that uint32_least_t is equivalent to
+             'unsigned int'.  */
+          int verify[(char32_t)(-1) >= 0 && sizeof (char32_t) == sizeof 
(unsigned int) ? 1 : -1];
+          ]])
+       ],
+       [gl_cv_type_char32_t_works=yes],
+       [gl_cv_type_char32_t_works=no])
+    ])
+  if test $gl_cv_type_char32_t_works = no; then
+    GNULIB_OVERRIDES_CHAR32_T=1
+  fi
+])
+
 AC_DEFUN([gl_UCHAR_MODULE_INDICATOR],
 [
   dnl Use AC_REQUIRE here, so that the default settings are expanded once only.
@@ -47,31 +95,33 @@ AC_DEFUN([gl_UCHAR_MODULE_INDICATOR],
 
 AC_DEFUN([gl_UCHAR_H_DEFAULTS],
 [
-  GNULIB_BTOC32=0;           AC_SUBST([GNULIB_BTOC32])
-  GNULIB_C32ISALNUM=0;       AC_SUBST([GNULIB_C32ISALNUM])
-  GNULIB_C32ISALPHA=0;       AC_SUBST([GNULIB_C32ISALPHA])
-  GNULIB_C32ISBLANK=0;       AC_SUBST([GNULIB_C32ISBLANK])
-  GNULIB_C32ISCNTRL=0;       AC_SUBST([GNULIB_C32ISCNTRL])
-  GNULIB_C32ISDIGIT=0;       AC_SUBST([GNULIB_C32ISDIGIT])
-  GNULIB_C32ISGRAPH=0;       AC_SUBST([GNULIB_C32ISGRAPH])
-  GNULIB_C32ISLOWER=0;       AC_SUBST([GNULIB_C32ISLOWER])
-  GNULIB_C32ISPRINT=0;       AC_SUBST([GNULIB_C32ISPRINT])
-  GNULIB_C32ISPUNCT=0;       AC_SUBST([GNULIB_C32ISPUNCT])
-  GNULIB_C32ISSPACE=0;       AC_SUBST([GNULIB_C32ISSPACE])
-  GNULIB_C32ISUPPER=0;       AC_SUBST([GNULIB_C32ISUPPER])
-  GNULIB_C32ISXDIGIT=0;      AC_SUBST([GNULIB_C32ISXDIGIT])
-  GNULIB_C32RTOMB=0;         AC_SUBST([GNULIB_C32RTOMB])
-  GNULIB_C32SNRTOMBS=0;      AC_SUBST([GNULIB_C32SNRTOMBS])
-  GNULIB_C32SRTOMBS=0;       AC_SUBST([GNULIB_C32SRTOMBS])
-  GNULIB_C32STOMBS=0;        AC_SUBST([GNULIB_C32STOMBS])
-  GNULIB_C32TOB=0;           AC_SUBST([GNULIB_C32TOB])
-  GNULIB_MBRTOC32=0;         AC_SUBST([GNULIB_MBRTOC32])
-  GNULIB_MBSNRTOC32S=0;      AC_SUBST([GNULIB_MBSNRTOC32S])
-  GNULIB_MBSRTOC32S=0;       AC_SUBST([GNULIB_MBSRTOC32S])
-  GNULIB_MBSTOC32S=0;        AC_SUBST([GNULIB_MBSTOC32S])
+  GNULIB_OVERRIDES_CHAR16_T=0; AC_SUBST([GNULIB_OVERRIDES_CHAR16_T])
+  GNULIB_OVERRIDES_CHAR32_T=0; AC_SUBST([GNULIB_OVERRIDES_CHAR32_T])
+  GNULIB_BTOC32=0;             AC_SUBST([GNULIB_BTOC32])
+  GNULIB_C32ISALNUM=0;         AC_SUBST([GNULIB_C32ISALNUM])
+  GNULIB_C32ISALPHA=0;         AC_SUBST([GNULIB_C32ISALPHA])
+  GNULIB_C32ISBLANK=0;         AC_SUBST([GNULIB_C32ISBLANK])
+  GNULIB_C32ISCNTRL=0;         AC_SUBST([GNULIB_C32ISCNTRL])
+  GNULIB_C32ISDIGIT=0;         AC_SUBST([GNULIB_C32ISDIGIT])
+  GNULIB_C32ISGRAPH=0;         AC_SUBST([GNULIB_C32ISGRAPH])
+  GNULIB_C32ISLOWER=0;         AC_SUBST([GNULIB_C32ISLOWER])
+  GNULIB_C32ISPRINT=0;         AC_SUBST([GNULIB_C32ISPRINT])
+  GNULIB_C32ISPUNCT=0;         AC_SUBST([GNULIB_C32ISPUNCT])
+  GNULIB_C32ISSPACE=0;         AC_SUBST([GNULIB_C32ISSPACE])
+  GNULIB_C32ISUPPER=0;         AC_SUBST([GNULIB_C32ISUPPER])
+  GNULIB_C32ISXDIGIT=0;        AC_SUBST([GNULIB_C32ISXDIGIT])
+  GNULIB_C32RTOMB=0;           AC_SUBST([GNULIB_C32RTOMB])
+  GNULIB_C32SNRTOMBS=0;        AC_SUBST([GNULIB_C32SNRTOMBS])
+  GNULIB_C32SRTOMBS=0;         AC_SUBST([GNULIB_C32SRTOMBS])
+  GNULIB_C32STOMBS=0;          AC_SUBST([GNULIB_C32STOMBS])
+  GNULIB_C32TOB=0;             AC_SUBST([GNULIB_C32TOB])
+  GNULIB_MBRTOC32=0;           AC_SUBST([GNULIB_MBRTOC32])
+  GNULIB_MBSNRTOC32S=0;        AC_SUBST([GNULIB_MBSNRTOC32S])
+  GNULIB_MBSRTOC32S=0;         AC_SUBST([GNULIB_MBSRTOC32S])
+  GNULIB_MBSTOC32S=0;          AC_SUBST([GNULIB_MBSTOC32S])
   dnl Assume proper GNU behavior unless another module says otherwise.
-  HAVE_C32RTOMB=1;           AC_SUBST([HAVE_C32RTOMB])
-  HAVE_MBRTOC32=1;           AC_SUBST([HAVE_MBRTOC32])
-  REPLACE_C32RTOMB=0;        AC_SUBST([REPLACE_C32RTOMB])
-  REPLACE_MBRTOC32=0;        AC_SUBST([REPLACE_MBRTOC32])
+  HAVE_C32RTOMB=1;             AC_SUBST([HAVE_C32RTOMB])
+  HAVE_MBRTOC32=1;             AC_SUBST([HAVE_MBRTOC32])
+  REPLACE_C32RTOMB=0;          AC_SUBST([REPLACE_C32RTOMB])
+  REPLACE_MBRTOC32=0;          AC_SUBST([REPLACE_MBRTOC32])
 ])
diff --git a/modules/uchar b/modules/uchar
index 2f94105..7215b36 100644
--- a/modules/uchar
+++ b/modules/uchar
@@ -28,6 +28,8 @@ uchar.h: uchar.in.h $(top_builddir)/config.status $(CXXDEFS_H)
              -e 's|@''PRAGMA_COLUMNS''@|@PRAGMA_COLUMNS@|g' \
              -e 's|@''NEXT_UCHAR_H''@|$(NEXT_UCHAR_H)|g' \
              -e 's|@''SMALL_WCHAR_T''@|$(SMALL_WCHAR_T)|g' \
+             -e 
's|@''GNULIB_OVERRIDES_CHAR16_T''@|$(GNULIB_OVERRIDES_CHAR16_T)|g' \
+             -e 
's|@''GNULIB_OVERRIDES_CHAR32_T''@|$(GNULIB_OVERRIDES_CHAR32_T)|g' \
              -e 's/@''GNULIB_BTOC32''@/$(GNULIB_BTOC32)/g' \
              -e 's/@''GNULIB_C32ISALNUM''@/$(GNULIB_C32ISALNUM)/g' \
              -e 's/@''GNULIB_C32ISALPHA''@/$(GNULIB_C32ISALPHA)/g' \