awk: Fix overly permissive func arg list parsing

It allows things like 'func f(a b)' and 'func f(a,)' which GNU awk forbids.

function                                             old     new   delta
parse_program                                        327     367     +40
chain_expr                                            40      67     +27
parse_expr                                           891     915     +24
EMSG_TOO_FEW_ARGS                                     30      18     -12
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 3/1 up/down: 91/-12)             Total: 79 bytes

Signed-off-by: Brian Foley <bpfoley@google.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

2 files changed, 26 insertions, 1 deletions

diff --git a/editors/awk.c b/editors/awk.c
index 90edec82c..d25508e5d 100644
--- a/editors/awk.c
+++ b/editors/awk.c
@@ -1613,12 +1613,25 @@ static void parse_program(char *p)
                         f = newfunc(t_string);
                         f->body.first = NULL;
                         f->nargs = 0;
-                        while (next_token(TC_VARIABLE | TC_SEQTERM) & TC_VARIABLE) {
+                        /* Match func arg list: a comma sep list of >= 0 args, and a close paren */
+                        while (next_token(TC_VARIABLE | TC_SEQTERM | TC_COMMA)) {
+                                /* Either an empty arg list, or trailing comma from prev iter
+                                 * must be followed by an arg */
+                                if (f->nargs == 0 && t_tclass == TC_SEQTERM)
+                                        break;
+
+                                /* TC_SEQSTART/TC_COMMA must be followed by TC_VARIABLE */
+                                if (t_tclass != TC_VARIABLE)
+                                        syntax_error(EMSG_UNEXP_TOKEN);
+
                                 v = findvar(ahash, t_string);
                                 v->x.aidx = f->nargs++;
 
+                                /* Arg followed either by end of arg list or 1 comma */
                                 if (next_token(TC_COMMA | TC_SEQTERM) & TC_SEQTERM)
                                         break;
+                                if (t_tclass != TC_COMMA)
+                                        syntax_error(EMSG_UNEXP_TOKEN);
                         }
                         seq = &f->body;
                         chain_group();
diff --git a/testsuite/awk.tests b/testsuite/awk.tests
index 03fedf771..0db6a26e4 100755
--- a/testsuite/awk.tests
+++ b/testsuite/awk.tests
@@ -280,6 +280,18 @@ testing "awk 'delete a[v--]' evaluates v-- once" \
 " \
         "" ""
 
+testing "awk func arg parsing 1" \
+        "awk 'func f(,) { }' 2>&1" "awk: cmd. line:1: Unexpected token\n" "" ""
+
+testing "awk func arg parsing 2" \
+        "awk 'func f(a,,b) { }' 2>&1" "awk: cmd. line:1: Unexpected token\n" "" ""
+
+testing "awk func arg parsing 3" \
+        "awk 'func f(a,) { }' 2>&1" "awk: cmd. line:1: Unexpected token\n" "" ""
+
+testing "awk func arg parsing 4" \
+        "awk 'func f(a b) { }' 2>&1" "awk: cmd. line:1: Unexpected token\n" "" ""
+
 testing "awk handles empty ()" \
         "awk 'BEGIN {print()}' 2>&1" "awk: cmd. line:1: Empty sequence\n" "" ""