bc: do not allow "()" as a valid expression

function                                             old     new   delta
bc_parse_expr_empty_ok                                 -    2178   +2178
bc_parse_expr                                       2178      49   -2129
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 0/1 up/down: 2178/-2129)         Total: 49 bytes

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

1 files changed, 13 insertions, 2 deletions

diff --git a/miscutils/bc.c b/miscutils/bc.c
index d2713ceee..eb5aff5e2 100644
--- a/miscutils/bc.c
+++ b/miscutils/bc.c
@@ -3616,6 +3616,7 @@ static void bc_parse_create(BcParse *p, size_t func,
 static BcStatus bc_parse_else(BcParse *p);
 static BcStatus bc_parse_stmt(BcParse *p);
 static BcStatus bc_parse_expr(BcParse *p, uint8_t flags, BcParseNext next);
+static BcStatus bc_parse_expr_empty_ok(BcParse *p, uint8_t flags, BcParseNext next);
 
 static BcStatus bc_parse_operator(BcParse *p, BcLexType type, size_t start,
                                   size_t *nexprs, bool next)
@@ -4027,7 +4028,7 @@ static BcStatus bc_parse_return(BcParse *p)
                 bc_parse_push(p, BC_INST_RET0);
         else {
 
-                s = bc_parse_expr(p, 0, bc_parse_next_expr);
+                s = bc_parse_expr_empty_ok(p, 0, bc_parse_next_expr);
                 if (s == BC_STATUS_PARSE_EMPTY_EXP) {
                         bc_parse_push(p, BC_INST_RET0);
                         s = bc_lex_next(&p->l);
@@ -4690,7 +4691,7 @@ static BcStatus bc_parse_parse(BcParse *p)
         return s;
 }
 
-static BcStatus bc_parse_expr(BcParse *p, uint8_t flags, BcParseNext next)
+static BcStatus bc_parse_expr_empty_ok(BcParse *p, uint8_t flags, BcParseNext next)
 {
         BcStatus s = BC_STATUS_SUCCESS;
         BcInst prev = BC_INST_PRINT;
@@ -4944,6 +4945,16 @@ static BcStatus bc_parse_expr(BcParse *p, uint8_t flags, BcParseNext next)
         return s;
 }
 
+static BcStatus bc_parse_expr(BcParse *p, uint8_t flags, BcParseNext next)
+{
+        BcStatus s;
+
+        s = bc_parse_expr_empty_ok(p, flags, next);
+        if (s == BC_STATUS_PARSE_EMPTY_EXP)
+                return bc_error("empty expression");
+        return s;
+}
+
 static void bc_parse_init(BcParse *p, size_t func)
 {
         bc_parse_create(p, func, bc_parse_parse, bc_lex_token);