Update 'configure' for libiconv detection; only set HAVE_ICONV_H if header exists *and* an impl we can link with exists.

configure

@@ -5308,7 +5308,7 @@ fi
 
 done
 
-for ac_header in unistd.h syslog.h iconv.h langinfo.h sys/statfs.h
+for ac_header in unistd.h syslog.h langinfo.h sys/statfs.h
 do :
   as_ac_Header=`$as_echo "ac_cv_header_$ac_header" | $as_tr_sh`
 ac_fn_c_check_header_mongrel "$LINENO" "$ac_header" "$as_ac_Header" "$ac_includes_default"
@@ -6103,6 +6103,118 @@ fi
 fi
 
 
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for iconv in -lc" >&5
+$as_echo_n "checking for iconv in -lc... " >&6; }
+if ${ac_cv_lib_c_iconv+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ac_check_lib_save_LIBS=$LIBS
+LIBS="-lc  $LIBS"
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+/* Override any GCC internal prototype to avoid an error.
+   Use char because int might match the return type of a GCC
+   builtin and then its argument prototype would still apply.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+char iconv ();
+int
+main ()
+{
+return iconv ();
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ac_cv_lib_c_iconv=yes
+else
+  ac_cv_lib_c_iconv=no
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+LIBS=$ac_check_lib_save_LIBS
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_lib_c_iconv" >&5
+$as_echo "$ac_cv_lib_c_iconv" >&6; }
+if test "x$ac_cv_lib_c_iconv" = xyes; then :
+
+   for ac_header in iconv.h
+do :
+  ac_fn_c_check_header_mongrel "$LINENO" "iconv.h" "ac_cv_header_iconv_h" "$ac_includes_default"
+if test "x$ac_cv_header_iconv_h" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_ICONV_H 1
+_ACEOF
+
+fi
+
+done
+
+
+else
+
+ { $as_echo "$as_me:${as_lineno-$LINENO}: checking for iconv in -liconv" >&5
+$as_echo_n "checking for iconv in -liconv... " >&6; }
+if ${ac_cv_lib_iconv_iconv+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ac_check_lib_save_LIBS=$LIBS
+LIBS="-liconv  $LIBS"
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+/* Override any GCC internal prototype to avoid an error.
+   Use char because int might match the return type of a GCC
+   builtin and then its argument prototype would still apply.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+char iconv ();
+int
+main ()
+{
+return iconv ();
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ac_cv_lib_iconv_iconv=yes
+else
+  ac_cv_lib_iconv_iconv=no
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+LIBS=$ac_check_lib_save_LIBS
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_lib_iconv_iconv" >&5
+$as_echo "$ac_cv_lib_iconv_iconv" >&6; }
+if test "x$ac_cv_lib_iconv_iconv" = xyes; then :
+
+   LIBS="-liconv $LIBS"
+   for ac_header in iconv.h
+do :
+  ac_fn_c_check_header_mongrel "$LINENO" "iconv.h" "ac_cv_header_iconv_h" "$ac_includes_default"
+if test "x$ac_cv_header_iconv_h" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_ICONV_H 1
+_ACEOF
+
+fi
+
+done
+
+
+else
+  :
+fi
+
+fi
+
+
 
 ac_ext=cpp
 ac_cpp='$CXXCPP $CPPFLAGS'

configure.in

@@ -64,7 +64,7 @@ AC_CHECK_HEADERS(sys/mount.h,,,
 #endif
 ]])
 AC_CHECK_HEADERS(sys/ustat.h sys/sysmacros.h sys/syslog.h)
-AC_CHECK_HEADERS(unistd.h syslog.h iconv.h langinfo.h sys/statfs.h)
+AC_CHECK_HEADERS(unistd.h syslog.h langinfo.h sys/statfs.h)
 AC_CHECK_HEADERS(signum.h bits/signum.h, break )
 AC_CHECK_HEADERS(stdarg.h varargs.h, break )
 
@@ -128,9 +128,12 @@ AC_CHECK_LIB(c, gethostbyname, [:], [
   ]) ])
 
 dnl iconv? check the usual locations
-AC_CHECK_LIB(c, iconv, [:], [
+AC_CHECK_LIB(c, iconv, [
+   AC_CHECK_HEADERS(iconv.h)
+  ], [
  AC_CHECK_LIB(iconv, iconv, [
    LIBS="-liconv $LIBS"
+   AC_CHECK_HEADERS(iconv.h)
   ], [:]) ])
 
 dnl check for stl library