This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
[C PATCH] Don't accept a cast as a valid LHS (PR c/66341)
- From: Marek Polacek <polacek at redhat dot com>
- To: GCC Patches <gcc-patches at gcc dot gnu dot org>, Joseph Myers <joseph at codesourcery dot com>
- Date: Wed, 3 Jun 2015 19:32:23 +0200
- Subject: [C PATCH] Don't accept a cast as a valid LHS (PR c/66341)
- Authentication-results: sourceware.org; auth=none
Since a cast does not yield an lvalue, we shouldn't accept invalid
code as in the attached testcase.
The problem was that we weren't setting NON_LVALUE_EXPR properly;
for comparing expressions we shouldn't use ==, because then a cast
in an expression might confuse us.
Bootstrapped/regtested on x86_64-linux, ok for trunk?
2015-06-03 Marek Polacek <polacek@redhat.com>
PR c/66341
* c-typeck.c (build_c_cast): Use c_tree_equal rather than a plain
comparison.
* gcc.dg/lvalue-8.c: New test.
diff --git gcc/c/c-typeck.c gcc/c/c-typeck.c
index f55d4c6..f13251b 100644
--- gcc/c/c-typeck.c
+++ gcc/c/c-typeck.c
@@ -5195,7 +5195,7 @@ build_c_cast (location_t loc, tree type, tree expr)
}
/* Don't let a cast be an lvalue. */
- if (value == expr)
+ if (c_tree_equal (value, expr))
value = non_lvalue_loc (loc, value);
/* Don't allow the results of casting to floating-point or complex
diff --git gcc/testsuite/gcc.dg/lvalue-8.c gcc/testsuite/gcc.dg/lvalue-8.c
index e69de29..085ce95 100644
--- gcc/testsuite/gcc.dg/lvalue-8.c
+++ gcc/testsuite/gcc.dg/lvalue-8.c
@@ -0,0 +1,19 @@
+/* PR c/66341 */
+/* { dg-do compile } */
+
+void
+foo (int *p)
+{
+ p = 0;
+ /* A cast does not yield an lvalue. */
+ (int *) p = 0; /* { dg-error "lvalue required as left operand of assignment" } */
+ /* A cast to a qualified type has the same effect as a cast
+ to the unqualified version of the type. */
+ (const int *) p = 0; /* { dg-error "lvalue required as left operand of assignment" } */
+ (int *) (char *) p = 0; /* { dg-error "lvalue required as left operand of assignment" } */
+ (int *) (char *) (int *) p = 0; /* { dg-error "lvalue required as left operand of assignment" } */
+ (int *) (char *) (int *) (char *) p = 0; /* { dg-error "lvalue required as left operand of assignment" } */
+ (int *) (double *) p = 0; /* { dg-error "lvalue required as left operand of assignment" } */
+ (int *) (int *) p = 0; /* { dg-error "lvalue required as left operand of assignment" } */
+ (int *) (const int *) p = 0; /* { dg-error "lvalue required as left operand of assignment" } */
+}
Marek