Re: libiconv detection failure

[Daiki Ueno]

Eli Zaretskii <address@hidden> writes:

> The prototype of 'iconv' in GNU libiconv's iconv.h is this:
>
>   size_t iconv (iconv_t cd, const char** inbuf, size_t *inbytesleft,
>                 char** outbuf, size_t *outbytesleft);
>
> The 'const' qualifier of the 2nd argument is decided at libiconv
> configuration time, and may be absent.  But the 4th argument is
> _never_ given a 'const' qualifier.

Sorry about that.  I have no idea why I type-casted OUTBUF (maybe I was
confused by the Linux manual page saying: "Although inbuf and outbuf are
typed as char **, ...").

> Next, it looks to me that the test program in iconv.m4 is
> inappropriate for a C++ compiler, because (AFAIK) C++ does not allow
> type-casting of the kind that the original test program (before your
> changes) did to the 2nd argument.  (With a C compiler, you get a
> warning, which the configure script ignores.)

I'm not familiar with C++, but does that really cause an error?

Yes, I see warnings with:

  ./configure CC=g++ CFLAGS=-Wcast-qual

The attached patch tries to suppress it.  Perhaps
gnulib/tests/test-iconv.c also needs a fix.

I've tested it on MSYS after manually adding 'const' to the iconv
declaration in /usr/local/include/iconv.h, and it seems to be detected.

Here is a new test package:
http://du-a.org/~ueno/junk/test-iconv-2.tar.gz

Thanks,
--
Daiki Ueno

>From 621cb2d9483053aa33cfeb1c6c6c20316aeac432 Mon Sep 17 00:00:00 2001
From: Daiki Ueno <address@hidden>
Date: Tue, 21 Oct 2014 18:07:00 +0900
Subject: [PATCH] iconv: avoid false detection of non-working iconv

The INBUF arguments of iconv can be either 'const char **'
or 'char **'.  If CC is g++, the difference causes a compile error
and thus leads to a false detection of non-working iconv.
Reported by Eli Zaretskii and Werner LEMBERG in:
<https://lists.gnu.org/archive/html/bug-gnulib/2014-10/msg00023.html>.
* m4/iconv.m4 (AM_ICONV_LINK): Try all possible argument types of
iconv.  Bump serial number.
---
 ChangeLog   | 11 +++++++++++
 m4/iconv.m4 | 61 ++++++++++++++++++++++++++++++++-----------------------------
 2 files changed, 43 insertions(+), 29 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 23234b7..62e4824 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,14 @@
+2014-10-21  Daiki Ueno  <address@hidden>
+
+       iconv: avoid false detection of non-working iconv
+       The INBUF arguments of iconv can be either 'const char **'
+       or 'char **'.  If CC is g++, the difference causes a compile error
+       and thus leads to a false detection of non-working iconv.
+       Reported by Eli Zaretskii and Werner LEMBERG in:
+       <https://lists.gnu.org/archive/html/bug-gnulib/2014-10/msg00023.html>.
+       * m4/iconv.m4 (AM_ICONV_LINK): Try all possible argument types of
+       iconv.  Bump serial number.
+
 2014-10-18  Paul Eggert  <address@hidden>
 
        symlinkat: port to AIX 7.1
diff --git a/m4/iconv.m4 b/m4/iconv.m4
index 4b29c5f..4e37363 100644
--- a/m4/iconv.m4
+++ b/m4/iconv.m4
@@ -1,4 +1,4 @@
-# iconv.m4 serial 18 (gettext-0.18.2)
+# iconv.m4 serial 19 (gettext-0.18.2)
 dnl Copyright (C) 2000-2002, 2007-2014 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -72,27 +72,33 @@ AC_DEFUN([AM_ICONV_LINK],
       if test $am_cv_lib_iconv = yes; then
         LIBS="$LIBS $LIBICONV"
       fi
-      AC_RUN_IFELSE(
-        [AC_LANG_SOURCE([[
+      am_cv_func_iconv_works=no
+      for ac_iconv_const in '' 'const'; do
+        AC_RUN_IFELSE(
+          [AC_LANG_PROGRAM(
+             [[
 #include <iconv.h>
 #include <string.h>
-int main ()
-{
-  int result = 0;
+
+#ifndef ICONV_CONST
+# define ICONV_CONST $ac_iconv_const
+#endif
+             ]],
+             [[int result = 0;
   /* Test against AIX 5.1 bug: Failures are not distinguishable from successful
      returns.  */
   {
     iconv_t cd_utf8_to_88591 = iconv_open ("ISO8859-1", "UTF-8");
     if (cd_utf8_to_88591 != (iconv_t)(-1))
       {
-        static const char input[] = "\342\202\254"; /* EURO SIGN */
+        static ICONV_CONST char input[] = "\342\202\254"; /* EURO SIGN */
         char buf[10];
-        const char *inptr = input;
+        ICONV_CONST char *inptr = input;
         size_t inbytesleft = strlen (input);
         char *outptr = buf;
         size_t outbytesleft = sizeof (buf);
         size_t res = iconv (cd_utf8_to_88591,
-                            (char **) &inptr, &inbytesleft,
+                            &inptr, &inbytesleft,
                             &outptr, &outbytesleft);
         if (res == 0)
           result |= 1;
@@ -105,14 +111,14 @@ int main ()
     iconv_t cd_ascii_to_88591 = iconv_open ("ISO8859-1", "646");
     if (cd_ascii_to_88591 != (iconv_t)(-1))
       {
-        static const char input[] = "\263";
+        static ICONV_CONST char input[] = "\263";
         char buf[10];
-        const char *inptr = input;
+        ICONV_CONST char *inptr = input;
         size_t inbytesleft = strlen (input);
         char *outptr = buf;
         size_t outbytesleft = sizeof (buf);
         size_t res = iconv (cd_ascii_to_88591,
-                            (char **) &inptr, &inbytesleft,
+                            &inptr, &inbytesleft,
                             &outptr, &outbytesleft);
         if (res == 0)
           result |= 2;
@@ -124,14 +130,14 @@ int main ()
     iconv_t cd_88591_to_utf8 = iconv_open ("UTF-8", "ISO-8859-1");
     if (cd_88591_to_utf8 != (iconv_t)(-1))
       {
-        static const char input[] = "\304";
+        static ICONV_CONST char input[] = "\304";
         static char buf[2] = { (char)0xDE, (char)0xAD };
-        const char *inptr = input;
+        ICONV_CONST char *inptr = input;
         size_t inbytesleft = 1;
         char *outptr = buf;
         size_t outbytesleft = 1;
         size_t res = iconv (cd_88591_to_utf8,
-                            (char **) &inptr, &inbytesleft,
+                            &inptr, &inbytesleft,
                             &outptr, &outbytesleft);
         if (res != (size_t)(-1) || outptr - buf > 1 || buf[1] != (char)0xAD)
           result |= 4;
@@ -144,14 +150,14 @@ int main ()
     iconv_t cd_88591_to_utf8 = iconv_open ("utf8", "iso88591");
     if (cd_88591_to_utf8 != (iconv_t)(-1))
       {
-        static const char input[] = "\304rger mit b\366sen B\374bchen ohne 
Augenma\337";
+        static ICONV_CONST char input[] = "\304rger mit b\366sen B\374bchen 
ohne Augenma\337";
         char buf[50];
-        const char *inptr = input;
+        ICONV_CONST char *inptr = input;
         size_t inbytesleft = strlen (input);
         char *outptr = buf;
         size_t outbytesleft = sizeof (buf);
         size_t res = iconv (cd_88591_to_utf8,
-                            (char **) &inptr, &inbytesleft,
+                            &inptr, &inbytesleft,
                             &outptr, &outbytesleft);
         if ((int)res > 0)
           result |= 8;
@@ -171,17 +177,14 @@ int main ()
       && iconv_open ("utf8", "eucJP") == (iconv_t)(-1))
     result |= 16;
   return result;
-}]])],
-        [am_cv_func_iconv_works=yes],
-        [am_cv_func_iconv_works=no],
-        [
-changequote(,)dnl
-         case "$host_os" in
-           aix* | hpux*) am_cv_func_iconv_works="guessing no" ;;
-           *)            am_cv_func_iconv_works="guessing yes" ;;
-         esac
-changequote([,])dnl
-        ])
+]])],
+          [am_cv_func_iconv_works=yes], ,
+          [case "$host_os" in
+             aix* | hpux*) am_cv_func_iconv_works="guessing no" ;;
+             *)            am_cv_func_iconv_works="guessing yes" ;;
+           esac])
+        test "$am_cv_func_iconv_works" = no || break
+      done
       LIBS="$am_save_LIBS"
     ])
     case "$am_cv_func_iconv_works" in
-- 
1.9.3