Re: libiconv detection failure

[Daiki Ueno]

Hello,

Werner LEMBERG <address@hidden> writes:

> Eli reported a failure in the detection code of iconv on MinGW while
> building groff:
>
>   conftest.cpp:62:51: error: invalid conversion from 'char**' to 'const 
> char**' [-fpermissive]
>   In file included from conftest.cpp:43:0:
>   d:\usr\bin\../lib/gcc/mingw32/4.7.2/../../../../include/iconv.h:83:15: 
> error: initializing argument 2 of 'size_t libiconv(libiconv_t, const char**, 
> size_t*, char**, size_t*)' [-fpermissive]

[...]

> It seems to me that the problem is a bug in gnulib's `iconv.m4'
> serial 18 file: Looking into this file I see that the body of
> `AM_ICONV' calls the macro `AM_ICONV_LINK' before the test that checks
> whether `const' is needed.  Obviously, it should be vice versa.

Given that the intention of the above test is to check if the iconv
function works properly, maybe a workaround would be to use the fixed
prototype of iconv (as attached)?  I'm still not able to reproduce the
original error on my MinGW environment, though.

Regards,
--
Daiki Ueno

>From 39e7957f1f724ae39524a82c230441df2557686c Mon Sep 17 00:00:00 2001
From: Daiki Ueno <address@hidden>
Date: Tue, 21 Oct 2014 13:01:10 +0900
Subject: [PATCH] iconv: avoid false link error with g++ and libiconv

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): Use the fixed prototype of the
iconv function while checking if iconv works properly.
---
 ChangeLog   |  8 ++++++++
 m4/iconv.m4 | 14 +++++++++++++-
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/ChangeLog b/ChangeLog
index 23234b7..852005c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2014-10-21  Daiki Ueno  <address@hidden>
+
+       iconv: avoid false link error with g++ and libiconv
+       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): Use the fixed prototype of the
+       iconv function while checking if iconv works properly.
+
 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..1aa41f3 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,
@@ -76,6 +76,18 @@ AC_DEFUN([AM_ICONV_LINK],
         [AC_LANG_SOURCE([[
 #include <iconv.h>
 #include <string.h>
+
+/* We are not really interested in whether INPTR and OUTPTR need
+   'const' qualifier here.  Use the fixed prototype to avoid false
+   link error when compiled with -fpermissive or g++.  */
+#undef iconv
+extern
+#ifdef __cplusplus
+"C"
+#endif
+size_t iconv (iconv_t cd, char * *inbuf, size_t *inbytesleft,
+              char * *outbuf, size_t *outbytesleft);
+
 int main ()
 {
   int result = 0;
-- 
1.9.3