@@ -8405,6 +8405,18 @@ fold_offsetof (tree expr, tree stop_ref)
return convert (size_type_node, fold_offsetof_1 (expr, stop_ref));
}
+/* Warn for A ?: C expressions (with B omitted) where A is a boolean
+ expression, because B will always be true. */
+
+void
+warn_for_omitted_condop (location_t location, tree cond)
+{
+ if (truth_value_p (TREE_CODE (cond)))
+ warning_at (location, OPT_Wparentheses,
+ "the omitted middle operand in ?: will always be %<true%>, "
+ "suggest explicit middle operand");
+}
+
/* Print an error message for an invalid lvalue. USE says
how the lvalue is being used and so selects the error message. */
@@ -736,6 +736,7 @@ extern void c_parse_file (void);
/* This is misnamed, it actually performs end-of-compilation processing. */
extern void finish_file (void);
+extern void warn_for_omitted_condop (location_t, tree);
/* These macros provide convenient access to the various _STMT nodes. */
@@ -4795,7 +4795,7 @@ static struct c_expr
c_parser_conditional_expression (c_parser *parser, struct c_expr *after)
{
struct c_expr cond, exp1, exp2, ret;
- location_t cond_loc, colon_loc;
+ location_t cond_loc, colon_loc, middle_loc;
gcc_assert (!after || c_dialect_objc ());
@@ -4809,8 +4809,11 @@ c_parser_conditional_expression (c_parser *parser, struct c_expr *after)
if (c_parser_next_token_is (parser, CPP_COLON))
{
tree eptype = NULL_TREE;
- pedwarn (c_parser_peek_token (parser)->location, OPT_pedantic,
+
+ middle_loc = c_parser_peek_token (parser)->location;
+ pedwarn (middle_loc, OPT_pedantic,
"ISO C forbids omitting the middle term of a ?: expression");
+ warn_for_omitted_condop (middle_loc, cond.value);
if (TREE_CODE (cond.value) == EXCESS_PRECISION_EXPR)
{
eptype = TREE_TYPE (cond.value);
@@ -6815,15 +6815,20 @@ cp_parser_question_colon_clause (cp_parser* parser, tree logical_or_expr)
{
tree expr;
tree assignment_expr;
+ struct cp_token *token;
/* Consume the `?' token. */
cp_lexer_consume_token (parser->lexer);
+ token = cp_lexer_peek_token (parser->lexer);
if (cp_parser_allow_gnu_extensions_p (parser)
- && cp_lexer_next_token_is (parser->lexer, CPP_COLON))
+ && token->type == CPP_COLON)
{
+ pedwarn (token->location, OPT_pedantic,
+ "ISO C++ does not allow ?: with omitted middle operand");
/* Implicit true clause. */
expr = NULL_TREE;
c_inhibit_evaluation_warnings += logical_or_expr == truthvalue_true_node;
+ warn_for_omitted_condop (token->location, logical_or_expr);
}
else
{
@@ -3275,6 +3275,12 @@ look like this:
@end group
@end smallexample
+Also warn for dangerous uses of the
+?: with omitted middle operand GNU extension. When the condition
+in the ?: operator is a boolean expression the omitted value will
+be always 1. Often the user expects it to be a value computed
+inside the conditional expression instead.
+
This warning is enabled by @option{-Wall}.
@item -Wsequence-point
new file mode 100644
@@ -0,0 +1,58 @@
+/* { dg-options "-Wparentheses" } */
+
+extern void f2 (int);
+
+void bar (int x, int y, int z)
+{
+#define T(op) f2 (x op y ? : 1)
+#define T2(op) f2 (x op y ? 2 : 1)
+
+ T(<); /* { dg-warning "omitted middle operand" } */
+ T(>); /* { dg-warning "omitted middle operand" } */
+ T(<=); /* { dg-warning "omitted middle operand" } */
+ T(>=); /* { dg-warning "omitted middle operand" } */
+ T(==); /* { dg-warning "omitted middle operand" } */
+ T(!=); /* { dg-warning "omitted middle operand" } */
+ T(||); /* { dg-warning "omitted middle operand" } */
+ T(&&); /* { dg-warning "omitted middle operand" } */
+ f2 (!x ? : 1); /* { dg-warning "omitted middle operand" } */
+ T2(<); /* { dg-bogus "omitted middle operand" } */
+ T2(>); /* { dg-bogus "omitted middle operand" } */
+ T2(==); /* { dg-bogus "omitted middle operand" } */
+ T2(||); /* { dg-bogus "omitted middle operand" } */
+ T2(&&); /* { dg-bogus "omitted middle operand" } */
+ T(+); /* { dg-bogus "omitted middle operand" } */
+ T(-); /* { dg-bogus "omitted middle operand" } */
+ T(*); /* { dg-bogus "omitted middle operand" } */
+ T(/); /* { dg-bogus "omitted middle operand" } */
+ T(^); /* { dg-bogus "omitted middle operand" } */
+}
+/* { dg-options "-Wparentheses" } */
+
+extern void f2 (int);
+
+void bar (int x, int y, int z)
+{
+#define T(op) f2 (x op y ? : 1)
+#define T2(op) f2 (x op y ? 2 : 1)
+
+ T(<); /* { dg-warning "omitted middle operand" } */
+ T(>); /* { dg-warning "omitted middle operand" } */
+ T(<=); /* { dg-warning "omitted middle operand" } */
+ T(>=); /* { dg-warning "omitted middle operand" } */
+ T(==); /* { dg-warning "omitted middle operand" } */
+ T(!=); /* { dg-warning "omitted middle operand" } */
+ T(||); /* { dg-warning "omitted middle operand" } */
+ T(&&); /* { dg-warning "omitted middle operand" } */
+ f2 (!x ? : 1); /* { dg-warning "omitted middle operand" } */
+ T2(<); /* { dg-bogus "omitted middle operand" } */
+ T2(>); /* { dg-bogus "omitted middle operand" } */
+ T2(==); /* { dg-bogus "omitted middle operand" } */
+ T2(||); /* { dg-bogus "omitted middle operand" } */
+ T2(&&); /* { dg-bogus "omitted middle operand" } */
+ T(+); /* { dg-bogus "omitted middle operand" } */
+ T(-); /* { dg-bogus "omitted middle operand" } */
+ T(*); /* { dg-bogus "omitted middle operand" } */
+ T(/); /* { dg-bogus "omitted middle operand" } */
+ T(^); /* { dg-bogus "omitted middle operand" } */
+}
new file mode 100644
@@ -0,0 +1,58 @@
+/* { dg-options "-Wparentheses" } */
+
+extern void f2 (int);
+
+void bar (int x, int y, int z)
+{
+#define T(op) f2 (x op y ? : 1)
+#define T2(op) f2 (x op y ? 2 : 1)
+
+ T(<); /* { dg-warning "omitted middle operand" } */
+ T(>); /* { dg-warning "omitted middle operand" } */
+ T(<=); /* { dg-warning "omitted middle operand" } */
+ T(>=); /* { dg-warning "omitted middle operand" } */
+ T(==); /* { dg-warning "omitted middle operand" } */
+ T(!=); /* { dg-warning "omitted middle operand" } */
+ T(||); /* { dg-warning "omitted middle operand" } */
+ T(&&); /* { dg-warning "omitted middle operand" } */
+ f2 (!x ? : 1); /* { dg-warning "omitted middle operand" } */
+ T2(<); /* { dg-bogus "omitted middle operand" } */
+ T2(>); /* { dg-bogus "omitted middle operand" } */
+ T2(==); /* { dg-bogus "omitted middle operand" } */
+ T2(||); /* { dg-bogus "omitted middle operand" } */
+ T2(&&); /* { dg-bogus "omitted middle operand" } */
+ T(+); /* { dg-bogus "omitted middle operand" } */
+ T(-); /* { dg-bogus "omitted middle operand" } */
+ T(*); /* { dg-bogus "omitted middle operand" } */
+ T(/); /* { dg-bogus "omitted middle operand" } */
+ T(^); /* { dg-bogus "omitted middle operand" } */
+}
+/* { dg-options "-Wparentheses" } */
+
+extern void f2 (int);
+
+void bar (int x, int y, int z)
+{
+#define T(op) f2 (x op y ? : 1)
+#define T2(op) f2 (x op y ? 2 : 1)
+
+ T(<); /* { dg-warning "omitted middle operand" } */
+ T(>); /* { dg-warning "omitted middle operand" } */
+ T(<=); /* { dg-warning "omitted middle operand" } */
+ T(>=); /* { dg-warning "omitted middle operand" } */
+ T(==); /* { dg-warning "omitted middle operand" } */
+ T(!=); /* { dg-warning "omitted middle operand" } */
+ T(||); /* { dg-warning "omitted middle operand" } */
+ T(&&); /* { dg-warning "omitted middle operand" } */
+ f2 (!x ? : 1); /* { dg-warning "omitted middle operand" } */
+ T2(<); /* { dg-bogus "omitted middle operand" } */
+ T2(>); /* { dg-bogus "omitted middle operand" } */
+ T2(==); /* { dg-bogus "omitted middle operand" } */
+ T2(||); /* { dg-bogus "omitted middle operand" } */
+ T2(&&); /* { dg-bogus "omitted middle operand" } */
+ T(+); /* { dg-bogus "omitted middle operand" } */
+ T(-); /* { dg-bogus "omitted middle operand" } */
+ T(*); /* { dg-bogus "omitted middle operand" } */
+ T(/); /* { dg-bogus "omitted middle operand" } */
+ T(^); /* { dg-bogus "omitted middle operand" } */
+}