iconv fixes

configure.ac

@@ -97,7 +97,10 @@ AC_ARG_ENABLE(iconv,
 HAVE_ICONV_H=0
 if test "$enable_iconv" = "yes"; then
     AM_ICONV
-    if test "$am_cv_func_iconv" = "yes"; then
+    # Use the "working iconv" test instead of the "iconv" ($am_cv_func_iconv) test
+    # so that our HAVE_ICONV_H substitution variable has the same value as the HAVE_ICONV
+    # C macro
+    if test "$am_func_iconv" = "yes"; then
         HAVE_ICONV_H=1
     fi
 fi

m4/iconv.m4

@@ -1,11 +1,18 @@
-# iconv.m4 serial 19 (gettext-0.18.2)
+# iconv.m4 serial 24
-dnl Copyright (C) 2000-2002, 2007-2014, 2016 Free Software Foundation, Inc.
+dnl Copyright (C) 2000-2002, 2007-2014, 2016-2021 Free Software Foundation,
+dnl Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
 dnl with or without modifications, as long as this notice is preserved.
 
 dnl From Bruno Haible.
 
+AC_PREREQ([2.64])
+
+dnl Note: AM_ICONV is documented in the GNU gettext manual
+dnl <https://www.gnu.org/software/gettext/manual/html_node/AM_005fICONV.html>.
+dnl Don't make changes that are incompatible with that documentation!
+
 AC_DEFUN([AM_ICONV_LINKFLAGS_BODY],
 [
   dnl Prerequisites of AC_LIB_LINKFLAGS_BODY.
@@ -85,8 +92,9 @@ AC_DEFUN([AM_ICONV_LINK],
 #endif
              ]],
              [[int result = 0;
-  /* Test against AIX 5.1 bug: Failures are not distinguishable from successful
+  /* Test against AIX 5.1...7.2 bug: Failures are not distinguishable from
-     returns.  */
+     successful returns.  This is even documented in
+     <https://www.ibm.com/support/knowledgecenter/ssw_aix_72/i_bostechref/iconv.html> */
   {
     iconv_t cd_utf8_to_88591 = iconv_open ("ISO8859-1", "UTF-8");
     if (cd_utf8_to_88591 != (iconv_t)(-1))
@@ -167,15 +175,27 @@ AC_DEFUN([AM_ICONV_LINK],
 #endif
   /* Test against HP-UX 11.11 bug: No converter from EUC-JP to UTF-8 is
      provided.  */
-  if (/* Try standardized names.  */
+  {
-      iconv_open ("UTF-8", "EUC-JP") == (iconv_t)(-1)
+    /* Try standardized names.  */
-      /* Try IRIX, OSF/1 names.  */
+    iconv_t cd1 = iconv_open ("UTF-8", "EUC-JP");
-      && iconv_open ("UTF-8", "eucJP") == (iconv_t)(-1)
+    /* Try IRIX, OSF/1 names.  */
-      /* Try AIX names.  */
+    iconv_t cd2 = iconv_open ("UTF-8", "eucJP");
-      && iconv_open ("UTF-8", "IBM-eucJP") == (iconv_t)(-1)
+    /* Try AIX names.  */
-      /* Try HP-UX names.  */
+    iconv_t cd3 = iconv_open ("UTF-8", "IBM-eucJP");
-      && iconv_open ("utf8", "eucJP") == (iconv_t)(-1))
+    /* Try HP-UX names.  */
-    result |= 16;
+    iconv_t cd4 = iconv_open ("utf8", "eucJP");
+    if (cd1 == (iconv_t)(-1) && cd2 == (iconv_t)(-1)
+        && cd3 == (iconv_t)(-1) && cd4 == (iconv_t)(-1))
+      result |= 16;
+    if (cd1 != (iconv_t)(-1))
+      iconv_close (cd1);
+    if (cd2 != (iconv_t)(-1))
+      iconv_close (cd2);
+    if (cd3 != (iconv_t)(-1))
+      iconv_close (cd3);
+    if (cd4 != (iconv_t)(-1))
+      iconv_close (cd4);
+  }
   return result;
 ]])],
           [am_cv_func_iconv_works=yes], ,
@@ -212,8 +232,7 @@ AC_DEFUN([AM_ICONV_LINK],
   AC_SUBST([LTLIBICONV])
 ])
 
-dnl Define AM_ICONV using AC_DEFUN_ONCE for Autoconf >= 2.64, in order to
+dnl Define AM_ICONV using AC_DEFUN_ONCE, in order to avoid warnings like
-dnl avoid warnings like
 dnl "warning: AC_REQUIRE: `AM_ICONV' was expanded before it was required".
 dnl This is tricky because of the way 'aclocal' is implemented:
 dnl - It requires defining an auxiliary macro whose name ends in AC_DEFUN.
@@ -221,51 +240,44 @@ dnl   Otherwise aclocal's initial scan pass would miss the macro definition.
 dnl - It requires a line break inside the AC_DEFUN_ONCE and AC_DEFUN expansions.
 dnl   Otherwise aclocal would emit many "Use of uninitialized value $1"
 dnl   warnings.
-m4_define([gl_iconv_AC_DEFUN],
+AC_DEFUN_ONCE([AM_ICONV],
-  m4_version_prereq([2.64],
-    [[AC_DEFUN_ONCE(
-        [$1], [$2])]],
-    [m4_ifdef([gl_00GNULIB],
-       [[AC_DEFUN_ONCE(
-           [$1], [$2])]],
-       [[AC_DEFUN(
-           [$1], [$2])]])]))
-gl_iconv_AC_DEFUN([AM_ICONV],
 [
   AM_ICONV_LINK
   if test "$am_cv_func_iconv" = yes; then
-    AC_MSG_CHECKING([for iconv declaration])
+    AC_CACHE_CHECK([whether iconv is compatible with its POSIX signature],
-    AC_CACHE_VAL([am_cv_proto_iconv], [
+      [gl_cv_iconv_nonconst],
-      AC_COMPILE_IFELSE(
+      [AC_COMPILE_IFELSE(
-        [AC_LANG_PROGRAM(
+         [AC_LANG_PROGRAM(
-           [[
+            [[
 #include <stdlib.h>
 #include <iconv.h>
 extern
 #ifdef __cplusplus
 "C"
 #endif
-#if defined(__STDC__) || defined(_MSC_VER) || defined(__cplusplus)
 size_t iconv (iconv_t cd, char * *inbuf, size_t *inbytesleft, char * *outbuf, size_t *outbytesleft);
-#else
+            ]],
-size_t iconv();
+            [[]])],
-#endif
+         [gl_cv_iconv_nonconst=yes],
-           ]],
+         [gl_cv_iconv_nonconst=no])
-           [[]])],
-        [am_cv_proto_iconv_arg1=""],
-        [am_cv_proto_iconv_arg1="const"])
-      am_cv_proto_iconv="extern size_t iconv (iconv_t cd, $am_cv_proto_iconv_arg1 char * *inbuf, size_t *inbytesleft, char * *outbuf, size_t *outbytesleft);"])
-    am_cv_proto_iconv=`echo "[$]am_cv_proto_iconv" | tr -s ' ' | sed -e 's/( /(/'`
-    AC_MSG_RESULT([
-         $am_cv_proto_iconv])
-    AC_DEFINE_UNQUOTED([ICONV_CONST], [$am_cv_proto_iconv_arg1],
-      [Define as const if the declaration of iconv() needs const.])
-    dnl Also substitute ICONV_CONST in the gnulib generated <iconv.h>.
-    m4_ifdef([gl_ICONV_H_DEFAULTS],
-      [AC_REQUIRE([gl_ICONV_H_DEFAULTS])
-       if test -n "$am_cv_proto_iconv_arg1"; then
-         ICONV_CONST="const"
-       fi
       ])
+  else
+    dnl When compiling GNU libiconv on a system that does not have iconv yet,
+    dnl pick the POSIX compliant declaration without 'const'.
+    gl_cv_iconv_nonconst=yes
   fi
+  if test $gl_cv_iconv_nonconst = yes; then
+    iconv_arg1=""
+  else
+    iconv_arg1="const"
+  fi
+  AC_DEFINE_UNQUOTED([ICONV_CONST], [$iconv_arg1],
+    [Define as const if the declaration of iconv() needs const.])
+  dnl Also substitute ICONV_CONST in the gnulib generated <iconv.h>.
+  m4_ifdef([gl_ICONV_H_DEFAULTS],
+    [AC_REQUIRE([gl_ICONV_H_DEFAULTS])
+     if test $gl_cv_iconv_nonconst != yes; then
+       ICONV_CONST="const"
+     fi
+    ])
 ])