awk: allow empty fuinctions with no arguments, disallow function redefinitions

function                                             old     new   delta
.rodata                                           103681  103700     +19
parse_program                                        303     307      +4
evaluate                                            3145    3141      -4
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/1 up/down: 23/-4)              Total: 19 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

editors/awk.c

@@ -139,6 +139,7 @@ typedef struct chain_s {
 /* Function */
 typedef struct func_s {
 	unsigned nargs;
+	smallint defined;
 	struct chain_s body;
 } func;
 
@@ -1662,9 +1663,11 @@ static void parse_program(char *p)
 			debug_printf_parse("%s: TC_FUNCDECL\n", __func__);
 			next_token(TC_FUNCTION);
 			f = newfunc(t_string);
-//FIXME: dup check: functions can't be redefined, this is not ok: awk 'func f(){}; func f(){}'
-			f->body.first = NULL;
-			f->nargs = 0;
+			if (f->defined)
+				syntax_error("Duplicate function");
+			f->defined = 1;
+			//f->body.first = NULL; - already is
+			//f->nargs = 0; - already is
 			/* func arg list: comma sep list of args, and a close paren */
 			for (;;) {
 				if (next_token(TC_VARIABLE | TC_RPAREN) == TC_RPAREN) {
@@ -2912,7 +2915,7 @@ static var *evaluate(node *op, var *res)
 
 			debug_printf_eval("FUNC\n");
 
-			if (op->r.f->nargs == 0 && !op->r.f->body.first)
+			if (!op->r.f->defined)
 				syntax_error(EMSG_UNDEF_FUNC);
 
 			/* The body might be empty, still has to eval the args */

testsuite/awk.tests

@@ -44,6 +44,16 @@ testing "awk handles empty function f(arg){}" \
 	"L1\n\nL2\n\n" \
 	"" ""
 
+prg='
+function empty_fun(){}
+END {empty_fun()
+  print "Ok"
+}'
+testing "awk handles empty function f(){}" \
+	"awk '$prg'" \
+	"Ok\n" \
+	"" ""
+
 prg='
 function outer_fun() {
   return 1