Document warning on function redefinitiion.

man/remind.1.in

@@ -4534,6 +4534,11 @@ or thirdfunc will exist.  \fBRemind\fR does not issue an error if you
 try to \fBFUNSET\fR a nonexistent user-defined function; it simply
 does nothing in that case.
 .PP
+If you define a user-defined function and then later on redefine it,
+\fBRemind\fR will issue a warning.  If you do not want this warning,
+then use \fBFUNSET\fR to remove the existing definition before you
+redefine the function.
+.PP
 .SH PRECISE SCHEDULING
 .PP
 The \fBWARN\fR keyword allows precise control over advance warning in

src/userfns.c

@@ -129,6 +129,9 @@ int DoFset(ParsePtr p)
             /* We already have it!  Our work here is done. */
             return OK;
         }
+        /* Warn about redefinition */
+        Wprint("Function %s redefined (previously defined at %s:%d)",
+               existing->name, existing->filename, existing->lineno);
     }
 
     /* Should be followed by '(' */

tests/test.cmp

@@ -3381,6 +3381,7 @@ Leaving UserFN _ofunc(1991-02-28) => 0
 
 # omitfunc ignores local/global omits
 fset _ofunc(x) 0
+../tests/test.rem(785): Function _ofunc redefined (previously defined at ../tests/test.rem:652)
 OMIT 1 March
 OMIT 2 March 1991
 REM 1 March OMIT Sun OMITFUNC _ofunc AFTER MSG Should trigger 1 March
@@ -18494,6 +18495,7 @@ ENDIF
 
 # Trig with a good warnfunc
 FSET w(x) choose(x, 5, 3, 1, 0)
+../tests/test.rem(4001): Function w redefined (previously defined at ../tests/test.rem:3980)
 
 # Short-circuit operators
 IF trig("sun warn w") || trig("thu warn w")
@@ -24109,6 +24111,7 @@ FSET f(a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14, a15, a16, a1
 
 # This should give an error
 FSET f(a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14, a15, a16, a17, a18, a19, a20, a21, a22, a23, a24, a25, a26, a27, a28, a29, a30, a31, a32, a33, a34, a35, a36, a37, a38, a39, a40, a41, a42, a43, a44, a45, a46, a47, a48, a49, a50, a51, a52, a53, a54, a55, a56, a57, a58, a59, a60, a61, a62, a63, a64) 3
+../tests/test.rem(5106): Function f redefined (previously defined at ../tests/test.rem:5103)
 ../tests/test.rem(5106): Too many arguments
 ../tests/test.rem(1008): Too many arguments
 ../tests/test.rem(5107): Unrecognized command; interpreting as REM