Best practice finding a suitable iconv()?

[Rüdiger Kuhlmann]

Hi,

I'm developing an application that makes use of iconv(), but needs to
guarantee that a few basic encodings are supported. However, the test from
iconv.m4 only tests for existance (and the way it checks shows a fundamental
flaw in checks for function existance, as the function may just be a macro,
or has a mangled symbol like select() for mingw), but I need more than that.
Currently I'm using the following construct:

if test "x$ac_arg_use_iconv" != "xno"; then
  AC_CHECK_FUNC([iconv], [ac_arg_use_iconv=system], [ac_arg_use_iconv=builtin])
  if test "x$ac_arg_use_iconv" = "xbuiltin"; then
    AC_CHECK_LIB([iconv], [iconv], [ac_arg_use_iconv=iconv])
    if test "x$ac_arg_use_iconv" = "xbuiltin"; then
      AC_CHECK_LIB([iconv], [libiconv], [ac_arg_use_iconv=libiconv])
    fi
    if test "x$ac_arg_use_iconv" != "xbuiltin"; then
      LIBS="-liconv $LIBS"
    fi
  fi
else
  ac_arg_use_iconv=builtin
fi

if test "x$ac_arg_use_iconv" != "xbuiltin"; then
  AC_CACHE_CHECK(for iconv declaration, ac_cv_iconv_const,
    [AC_LINK_IFELSE([AC_LANG_PROGRAM([[#include <stdlib.h>
        #include <iconv.h>]],
        [[#ifdef __cplusplus
          "C"
          #endif
          #if defined(__STDC__) || defined(__cplusplus)
          size_t iconv (iconv_t cd, char * *inbuf, size_t *inbytesleft, char * 
*outbuf, size_t *outbytesleft);
          #else
          size_t iconv();
          #endif]])],
      [ac_cv_iconv_const=no-const],
      [ac_cv_iconv_const=const])])
  if test $ac_cv_iconv_const = const; then
     AC_DEFINE([ICONV_CONST], const, [Define as const if the declaration of 
iconv() needs const.])
  else
     AC_DEFINE([ICONV_CONST], /* no-const */)
  fi
  AC_CACHE_CHECK(for iconv minimal functionality, ac_cv_iconv_min,
    [AC_RUN_IFELSE([AC_LANG_PROGRAM([[#include <stdlib.h>
          #include <iconv.h>]],
        [[iconv_t res;
          res = iconv_open ("UTF-8", "ISO-8859-1");
          if (res == (iconv_t)-1 || !res)
          {
              res = iconv_open ("UTF-8", "ISO8859-1");
              if (res == (iconv_t)-1 || !res) exit (2);
              res = iconv_open ("ISO8859-1", "UTF-8");
              if (res == (iconv_t)-1 || !res) exit (3);
          }
          else
          {
              res = iconv_open ("ISO-8859-1", "UTF-8");
              if (res == (iconv_t)-1 || !res) exit (4);
          }
          res = iconv_open ("UTF-8", "ISO-8859-15");
          if (res == (iconv_t)-1 || !res)
          {
              res = iconv_open ("UTF-8", "ISO8859-15");
              if (res == (iconv_t)-1 || !res) exit (5);
              res = iconv_open ("ISO8859-15", "UTF-8");
              if (res == (iconv_t)-1 || !res) exit (6);
          }
          else
          {
              res = iconv_open ("ISO-8859-15", "UTF-8");
              if (res == (iconv_t)-1 || !res) exit (7);
          }
          res = iconv_open ("UTF-8", "KOI8-U");
          if (res == (iconv_t)-1 || !res) exit (8);
          res = iconv_open ("KOI8-U", "UTF-8");
          if (res == (iconv_t)-1 || !res) exit (9);
          res = iconv_open ("UTF-8", "CP1251");
          if (res == (iconv_t)-1 || !res) exit (10);
          res = iconv_open ("CP1251", "UTF-8");
          if (res == (iconv_t)-1 || !res) exit (11);
          exit (0);]])],
      [ac_cv_iconv_min=ok],
      [ac_cv_iconv_min=broken],
      [ac_cv_iconv_min=cross])
  ])
  if test $ac_cv_iconv_min != ok; then
    ac_arg_use_iconv=buildin
    AC_DEFINE([ICONV_LATIN1_NAME], ["ISO-8859-1"],  [the name of the latin1 
encoding])
    AC_DEFINE([ICONV_LATIN9_NAME], ["ISO-8859-15"], [the name of the latin9 
encoding])
  else
    AC_CACHE_CHECK(for iconv name of latin-1 encoding, ac_cv_iconv_latin1_name,
      [AC_RUN_IFELSE([AC_LANG_PROGRAM([[#include <stdlib.h>
            #include <iconv.h>]],
          [[iconv_t res;
            res = iconv_open ("UTF-8", "ISO-8859-1");
            if (res == (iconv_t)-1 || !res) exit (1);
            exit (0);]])],
        [ac_cv_iconv_latin1_name=ISO-8859-1],
        [ac_cv_iconv_latin1_name=ISO8859-1],
        [ac_cv_iconv_latin1_name=cannothappen])
    ])
    AC_DEFINE_UNQUOTED([ICONV_LATIN1_NAME], ["$ac_cv_iconv_latin1_name"])
    AC_CACHE_CHECK(for iconv name of latin-9 encoding, ac_cv_iconv_latin9_name,
      [AC_RUN_IFELSE([AC_LANG_PROGRAM([[#include <stdlib.h>
            #include <iconv.h>]],
          [[iconv_t res;
            res = iconv_open ("UTF-8", "ISO-8859-15");
            if (res == (iconv_t)-1 || !res) exit (1);
            exit (0);]])],
        [ac_cv_iconv_latin9_name=ISO-8859-15],
        [ac_cv_iconv_latin9_name=ISO8859-15],
        [ac_cv_iconv_latin9_name=cannothappen])
    ])
    AC_DEFINE_UNQUOTED([ICONV_LATIN9_NAME], ["$ac_cv_iconv_latin9_name"])
  fi
else
  AC_DEFINE([ICONV_LATIN1_NAME], ["ISO-8859-1"])
  AC_DEFINE([ICONV_LATIN9_NAME], ["ISO-8859-15"])
fi

AC_MSG_CHECKING([whether to enable iconv and which iconv lib to use])
AC_MSG_RESULT([$ac_arg_use_iconv])

Is there any better way to do this? Or any accepted standard procedure?

-- 
         100 DM =  51  € 13 ¢.
         100  € = 195 DM 58 pf.
  mailto:address@hidden
    http://www.ruediger-kuhlmann.de/