There are some ideas here previously described by Mo DeJong.
Additionally:

. there is a way to avoid a warning for a certain platform:
  set apr_iconv_inbuf_const to "1" in hints.m4 for platforms
  where the parm is "const char **" but the autoconf logic
  doesn't detect

. we *know* that versions of glibc < 2.2 have "const char **"
  instead of "char **" so make that work without any hints.m4
  stuff (which would have to look at the glibc version)
 
This should get RedHat 7.0 compiling cleanly, but I don't have such a
system to test with.  

My RedHat 6.0 system ("const char **") now compiles xlate.c cleanly
for the first time in a while.  

A Tru64 system ("char **") still compiles xlate.c cleanly.

To get AIX compiling xlate.c cleanly (it hasn't done so in a while)
I'd expect to have to add apr_iconv_inbuf_const=1 to the AIX stanza in
hints.m4.  I haven't tested that though.  The same is true for
Solaris, which is "const char **" like AIX.

Comments?

Index: apr_common.m4
===================================================================
RCS file: /home/cvspublic/apr/apr_common.m4,v
retrieving revision 1.11
diff -u -r1.11 apr_common.m4
--- apr_common.m4	2001/01/11 13:55:58	1.11
+++ apr_common.m4	2001/02/08 00:01:57
@@ -285,3 +285,36 @@
   $1="$$1 $2"; export $1
 ])
 
+dnl
+dnl APR_CHECK_ICONV_INBUF
+dnl
+dnl  Decide whether or not the inbuf parameter to iconv() is const.
+dnl
+dnl  We try to compile something without const.  If it fails to 
+dnl  compile, we assume that the system's iconv() has const.  
+dnl  Unfortunately, we won't realize when there was a compile
+dnl  warning, so we allow a variable -- apr_iconv_inbuf_const -- to
+dnl  be set in hints.m4 to specify whether or not iconv() has const
+dnl  on this parameter.
+dnl
+AC_DEFUN(APR_CHECK_ICONV_INBUF,[
+AC_MSG_CHECKING(for type of inbuf parameter to iconv)
+if test "x$apr_iconv_inbuf_const" = "x"; then
+    AC_TRY_COMPILE([
+    #include <stddef.h>
+    #include <iconv.h>
+    ],[
+    #if defined(__GLIBC__) && __GLIBC__ == 2 && __GLIBC_MINOR < 2
+    #error We know this version of glibc has const char **, so fail this compile
+    #endif
+    iconv(0,(char **)0,(size_t *)0,(char **)0,(size_t *)0);
+    ], apr_iconv_inbuf_const="0", apr_iconv_inbuf_const="1")
+fi
+if test "$apr_iconv_inbuf_const" = "1"; then
+    AC_DEFINE(APR_ICONV_INBUF_CONST, 1, [Define if the inbuf parm to iconv() is const char **])
+    msg="const char **"
+else
+    msg="char **"
+fi
+AC_MSG_RESULT([$msg])
+])
Index: configure.in
===================================================================
RCS file: /home/cvspublic/apr/configure.in,v
retrieving revision 1.220
diff -u -r1.220 configure.in
--- configure.in	2001/01/28 12:18:38	1.220
+++ configure.in	2001/02/08 00:02:07
@@ -245,6 +245,9 @@
 AC_CHECK_FUNC(_getch)
 AC_CHECK_FUNCS(gmtime_r localtime_r)
 AC_CHECK_FUNCS(iconv, [ iconv="1" ], [ iconv="0" ])
+if test "$iconv" = "1"; then
+  APR_CHECK_ICONV_INBUF
+fi
 AC_CHECK_FUNCS(mmap, [ mmap="1" ], [ mmap="0" ])
 if test "$native_mmap_emul" = "1"; then
     mmap="1"
Index: i18n/unix/xlate.c
===================================================================
RCS file: /home/cvspublic/apr/i18n/unix/xlate.c,v
retrieving revision 1.18
diff -u -r1.18 xlate.c
--- i18n/unix/xlate.c	2001/01/28 11:33:52	1.18
+++ i18n/unix/xlate.c	2001/02/08 00:02:33
@@ -80,6 +80,12 @@
 #include <iconv.h>
 #endif
 
+#ifdef APR_ICONV_INBUF_CONST
+#define ICONV_INBUF_TYPE const char **
+#else
+#define ICONV_INBUF_TYPE char **
+#endif
+
 #ifndef min
 #define min(x,y) ((x) <= (y) ? (x) : (y))
 #endif
@@ -194,7 +200,7 @@
     }
 
     inbytes_left = outbytes_left = sizeof(inbuf);
-    translated = iconv(convset->ich, &inbufptr, 
+    translated = iconv(convset->ich, (ICONV_INBUF_TYPE)&inbufptr, 
                        &inbytes_left, &outbufptr, &outbytes_left);
     if (translated != (size_t) -1 &&
         inbytes_left == 0 &&
@@ -288,7 +294,7 @@
         char *inbufptr = (char *)inbuf;
         char *outbufptr = outbuf;
         
-        translated = iconv(convset->ich, &inbufptr, 
+        translated = iconv(convset->ich, (ICONV_INBUF_TYPE)&inbufptr, 
                            inbytes_left, &outbufptr, outbytes_left);
         /* If everything went fine but we ran out of buffer, don't
          * report it as an error.  Caller needs to look at the two

-- 
Jeff Trawick | trawickj@bellsouth.net | PGP public key at web site:
       http://www.geocities.com/SiliconValley/Park/9289/
             Born in Roswell... married an alien...