>From d6f8671505956401691e3c35d19499470f582a88 Mon Sep 17 00:00:00 2001
From: Bruno Haible <address@hidden>
Date: Thu, 9 Jan 2020 02:04:07 +0100
Subject: [PATCH 4/4] c32tob: Make consistent with mbrtoc32.

* lib/c32tob.c: Include <stdio.h>, <string.h>, <wchar.h>.
(c32tob): If the char32_t encoding and the wchar_t encoding may differ,
use c32rtomb, not wctob.
* modules/c32tob (Files): Add m4/mbrtoc32.m4.
(Depends-on): Add c32rtomb.
(configure.ac): Require gl_MBRTOC32_SANITYCHECK.
---
 ChangeLog      | 10 ++++++++++
 lib/c32tob.c   | 19 ++++++++++++++++++-
 modules/c32tob |  3 +++
 3 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/ChangeLog b/ChangeLog
index c303d41..9c3f603 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,15 @@
 2020-01-08  Bruno Haible  <address@hidden>
 
+	c32tob: Make consistent with mbrtoc32.
+	* lib/c32tob.c: Include <stdio.h>, <string.h>, <wchar.h>.
+	(c32tob): If the char32_t encoding and the wchar_t encoding may differ,
+	use c32rtomb, not wctob.
+	* modules/c32tob (Files): Add m4/mbrtoc32.m4.
+	(Depends-on): Add c32rtomb.
+	(configure.ac): Require gl_MBRTOC32_SANITYCHECK.
+
+2020-01-08  Bruno Haible  <address@hidden>
+
 	c32rtomb: Add tests.
 	* tests/test-c32rtomb.c: New file, based on tests/test-wcrtomb.c.
 	* tests/test-c32rtomb.sh: New file, based on tests/test-wcrtomb.sh.
diff --git a/lib/c32tob.c b/lib/c32tob.c
index 4da438f..55f61c7 100644
--- a/lib/c32tob.c
+++ b/lib/c32tob.c
@@ -21,10 +21,27 @@
 /* Specification.  */
 #include <uchar.h>
 
+#include <stdio.h>
+#include <string.h>
+#include <wchar.h>
+
 int
 c32tob (wint_t wc)
 {
-#if _GL_LARGE_CHAR32_T
+#if HAVE_WORKING_MBRTOC32 && !defined __GLIBC__
+  /* The char32_t encoding of a multibyte character may be different than its
+     wchar_t encoding.  */
+  if (wc != WEOF)
+    {
+      mbstate_t state;
+      char buf[8];
+
+      memset (&state, '\0', sizeof (mbstate_t));
+      if (c32rtomb (buf, wc, &state) == 1)
+        return (unsigned char) buf[0];
+    }
+  return EOF;
+#elif _GL_LARGE_CHAR32_T
   /* In all known encodings, unibyte characters correspond only to
      characters in the BMP.  */
   if (wc != WEOF && (wchar_t) wc == wc)
diff --git a/modules/c32tob b/modules/c32tob
index 3ef42ba..42e18a9 100644
--- a/modules/c32tob
+++ b/modules/c32tob
@@ -3,12 +3,15 @@ c32tob() function: convert 32-bit wide character to unibyte character.
 
 Files:
 lib/c32tob.c
+m4/mbrtoc32.m4
 
 Depends-on:
 uchar
+c32rtomb
 wctob
 
 configure.ac:
+AC_REQUIRE([gl_MBRTOC32_SANITYCHECK])
 gl_UCHAR_MODULE_INDICATOR([c32tob])
 
 Makefile.am:
-- 
2.7.4