FYI: charset configury cleanup

[Tom Tromey <tromey at redhat dot com>]

I'm checking this in.

I noticed a couple oddities in the iconv configure code.  It wasn't
reliably detecting the in-tree libiconv, and it was adding too many
things to CPPFLAGS in some cases.

This patch cleans these up.  I also added some comments to make it
simpler to figure out what is going on.

Built three ways on x86 F9.  I also verified the generated
gdb/Makefile by hand in each case.

Tom

2009-03-25  Tom Tromey  <tromey@redhat.com>

	* configure: Rebuild.
	* acinclude.m4 (AM_ICONV): Set am_cv_use_build_libiconv.
	Rearrange flags setting.  Add comments.

Index: acinclude.m4
===================================================================
RCS file: /cvs/src/src/gdb/acinclude.m4,v
retrieving revision 1.26
diff -u -r1.26 acinclude.m4
--- acinclude.m4	25 Mar 2009 00:58:34 -0000	1.26
+++ acinclude.m4	26 Mar 2009 00:36:51 -0000
@@ -177,8 +177,8 @@
   AC_ARG_WITH([libiconv-prefix],
 [  --with-libiconv-prefix=DIR  search for libiconv in DIR/include and DIR/lib], [
     for dir in `echo "$withval" | tr : ' '`; do
-      if test -d $dir/include; then LIBICONV_INCLUDE="-I$dir/include"; CPPFLAGS="$CPPFLAGS -I$dir/include"; fi
-      if test -d $dir/lib; then LIBICONV_LIBDIR="-L$dir/lib"; LDFLAGS="$LDFLAGS -L$dir/lib"; fi
+      if test -d $dir/include; then LIBICONV_INCLUDE="-I$dir/include"; fi
+      if test -d $dir/lib; then LIBICONV_LIBDIR="-L$dir/lib"; fi
     done
    ])
 
@@ -189,14 +189,23 @@
     am_cv_func_iconv="no, consider installing GNU libiconv"
     am_cv_lib_iconv=no
     am_cv_use_build_libiconv=no
+    # First, try to find iconv in libc.
     AC_TRY_LINK([#include <stdlib.h>
 #include <iconv.h>],
       [iconv_t cd = iconv_open("","");
        iconv(cd,NULL,NULL,NULL,NULL);
        iconv_close(cd);],
       am_cv_func_iconv=yes)
+
+    # If iconv was not in libc, try -liconv.  In this case, arrange to
+    # look in the libiconv prefix, if it was specified by the user.
     if test "$am_cv_func_iconv" != yes; then
+      am_save_CPPFLAGS="$CPPFLAGS"
       am_save_LIBS="$LIBS"
+      if test -n "$LIBICONV_INCLUDE"; then
+        CPPFLAGS="$CPPFLAGS $LIBICONV_INCLUDE"
+        LIBS="$LIBS $LIBICONV_LIBDIR"
+      fi
       LIBS="$LIBS -liconv"
       AC_TRY_LINK([#include <stdlib.h>
 #include <iconv.h>],
@@ -206,8 +215,10 @@
         am_cv_lib_iconv=yes
         am_cv_func_iconv=yes)
       LIBS="$am_save_LIBS"
+      CPPFLAGS="$am_save_CPPFLAGS"
     fi
-    # Look for libiconv in the build tree.
+
+    # If that didn't work, try to find libiconv in the build tree.
     if test "$am_cv_func_iconv" != yes && test -d ../libiconv; then
       am_save_LIBS="$LIBS"
       am_save_CPPFLAGS="$CPPFLAGS"
@@ -218,15 +229,22 @@
         [iconv_t cd = iconv_open("","");
          iconv(cd,NULL,NULL,NULL,NULL);
          iconv_close(cd);],
+	am_cv_use_build_libiconv=yes
         am_cv_lib_iconv=yes
         am_cv_func_iconv=yes)
       LIBS="$am_save_LIBS"
       CPPFLAGS="$am_save_CPPFLAGS"
     fi
   ])
+
+  # Set the various flags based on the cache variables.  We can't rely
+  # on the flags to remain set from the above code, due to caching.
   LIBICONV=
   if test "$am_cv_lib_iconv" = yes; then
     LIBICONV="-liconv"
+  else
+    LIBICONV_LIBDIR=
+    LIBICONV_INCLUDE=
   fi
   if test "$am_cv_use_build_libiconv" = yes; then
     LIBICONV_LIBDIR="$BUILD_LIBICONV_LIBDIR"
@@ -234,6 +252,7 @@
   fi
   CPPFLAGS="$CPPFLAGS $LIBICONV_INCLUDE"
   LIBS="$LIBS $LIBICONV_LIBDIR $LIBICONV"
+
   if test "$am_cv_func_iconv" = yes; then
     AC_DEFINE(HAVE_ICONV, 1, [Define if you have the iconv() function.])
     AC_MSG_CHECKING([for iconv declaration])