C: Drop qualifiers of assignment expressions. [PR98047]

ISO C17 6.5.15.1 specifies that the result is the
type the LHS would have after lvalue conversion.

2020-12-16  Martin Uecker  <muecker@gwdg.de>

gcc/c/
	PR c/98047
	* c-typeck.c (build_modify_expr): Drop qualifiers.

gcc/testsuite/
	PR c/98047
	* gcc.dg/qual-assign-7.c: New test.

diff --git a/gcc/c/c-typeck.c b/gcc/c/c-typeck.c
index 7d58e8de342b03d5d8d72187b96bd86d70a6880c..f68cb01529b39df044f70989b476907848dbc989 100644 (file)
--- a/gcc/c/c-typeck.c
+++ b/gcc/c/c-typeck.c
@@ -6275,16 +6275,9 @@ build_modify_expr (location_t location, tree lhs, tree lhs_origtype,
                    "enum conversion in assignment is invalid in C++");
     }
 
-  /* If the lhs is atomic, remove that qualifier.  */
-  if (is_atomic_op)
-    {
-      lhstype = build_qualified_type (lhstype, 
-                                     (TYPE_QUALS (lhstype)
-                                      & ~TYPE_QUAL_ATOMIC));
-      olhstype = build_qualified_type (olhstype, 
-                                      (TYPE_QUALS (lhstype)
-                                       & ~TYPE_QUAL_ATOMIC));
-    }
+  /* Remove qualifiers.  */
+  lhstype = build_qualified_type (lhstype, TYPE_UNQUALIFIED);
+  olhstype = build_qualified_type (olhstype, TYPE_UNQUALIFIED);
 
   /* Convert new value to destination type.  Fold it first, then
      restore any excess precision information, for the sake of

diff --git a/gcc/testsuite/gcc.dg/qual-assign-7.c b/gcc/testsuite/gcc.dg/qual-assign-7.c
new file mode 100644 (file)
index 0000000..3e064e8
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/qual-assign-7.c
@@ -0,0 +1,18 @@
+/* test that assignment drops qualifiers, Bug 98047 */
+/* { dg-do compile } */
+/* { dg-options "" } */
+
+
+volatile int jv;
+extern int j;
+extern typeof(jv = 1) j;
+
+_Atomic int ja;
+extern typeof(ja = 1) j;
+
+int * __restrict pa;
+extern int *p;
+extern typeof(pa = 0) p;
+
+
+