re PR c/69002 (C front end should warn about undefined access to atomic structure...

	PR c/69002
	* c-typeck.c (build_component_ref): Warn when acessing elements of
	atomic structures or unions.

	* gcc.dg/c11-atomic-1.c: Add dg-warnings.
	* gcc.dg/c11-atomic-4.c: New test.

From-SVN: r231902

diff --git a/gcc/c/ChangeLog b/gcc/c/ChangeLog
index fb9fda3b21165fc84ea14dfb566d4c36fcafe6f4..f99f426d54295104c90b981208140337107d3b3f 100644 (file)
--- a/gcc/c/ChangeLog
+++ b/gcc/c/ChangeLog
@@ -1,3 +1,9 @@
+2015-12-22  Marek Polacek  <polacek@redhat.com>
+
+       PR c/69002
+       * c-typeck.c (build_component_ref): Warn when acessing elements of
+       atomic structures or unions.
+
 2015-12-21  David Malcolm  <dmalcolm@redhat.com>
 
        * c-typeck.c: Include "gcc-rich-location.h".

diff --git a/gcc/c/c-typeck.c b/gcc/c/c-typeck.c
index a97774fea92c493d024b204e6e6bb97cfd5759c8..928fcd504d097906b452168b1ab4da1a5bfe14f2 100644 (file)
--- a/gcc/c/c-typeck.c
+++ b/gcc/c/c-typeck.c
@@ -2349,6 +2349,18 @@ build_component_ref (location_t loc, tree datum, tree component)
          return error_mark_node;
        }
 
+      /* Accessing elements of atomic structures or unions is undefined
+        behavior (C11 6.5.2.3#5).  */
+      if (TYPE_ATOMIC (type) && c_inhibit_evaluation_warnings == 0)
+       {
+         if (code == RECORD_TYPE)
+           warning_at (loc, 0, "accessing a member %qE of an atomic "
+                       "structure %qE", component, datum);
+         else
+           warning_at (loc, 0, "accessing a member %qE of an atomic "
+                       "union %qE", component, datum);
+       }
+
       /* Chain the COMPONENT_REFs if necessary down to the FIELD.
         This might be better solved in future the way the C++ front
         end does it - by giving the anonymous entities each a

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index d5c679e63e2f3632edc888cc010603cf8008f350..50733e6b46cc95d6a333611870fb35c18d575a8f 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2015-12-22  Marek Polacek  <polacek@redhat.com>
+
+       PR c/69002
+       * gcc.dg/c11-atomic-1.c: Add dg-warnings.
+       * gcc.dg/c11-atomic-4.c: New test.
+
 2015-12-22  Sujoy Saraswati  <sujoy.saraswati@hpe.com>
 
        * gcc.dg/pr61441.c: New testcase.

diff --git a/gcc/testsuite/gcc.dg/c11-atomic-1.c b/gcc/testsuite/gcc.dg/c11-atomic-1.c
index c7f9a1ef464c5c3b869cbcf4e266e601ea20dce7..9702a10a62a1eacc3c6b69b60434d2efefa6411d 100644 (file)
--- a/gcc/testsuite/gcc.dg/c11-atomic-1.c
+++ b/gcc/testsuite/gcc.dg/c11-atomic-1.c
@@ -61,15 +61,15 @@ func (_Atomic volatile long al1)
      accessing elements of atomic structures and unions is at
      translation or execution time; presume here that it's at
      execution time.  */
-  t1.i = at1.i;
-  at1.i = t1.i;
-  atp1->i = t1.i;
+  t1.i = at1.i; /* { dg-warning "accessing a member .i. of an atomic structure" } */
+  at1.i = t1.i; /* { dg-warning "accessing a member .i. of an atomic structure" } */
+  atp1->i = t1.i; /* { dg-warning "accessing a member .i. of an atomic structure" } */
   au1 = u1;
   u1 = au1;
   av1 = v1;
   v1 = av1;
-  v1.i = av1.i;
-  av1.i = v1.i;
+  v1.i = av1.i; /* { dg-warning "accessing a member .i. of an atomic union" } */
+  av1.i = v1.i; /* { dg-warning "accessing a member .i. of an atomic union" } */
   /* _Atomic is valid on register variables, even if not particularly
      useful.  */
   register _Atomic volatile int ra1 = 1, ra2 = 2;

diff --git a/gcc/testsuite/gcc.dg/c11-atomic-4.c b/gcc/testsuite/gcc.dg/c11-atomic-4.c
new file mode 100644 (file)
index 0000000..81003aa
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c11-atomic-4.c
@@ -0,0 +1,92 @@
+/* PR c/69002 */
+/* Test we diagnose accessing elements of atomic structures or unions,
+   which is undefined behavior (C11 6.5.2.3#5).  */
+/* { dg-do compile } */
+/* { dg-options "-std=c11 -pedantic-errors" } */
+
+struct S { int x; };
+union U { int x; };
+
+int
+fn1 (_Atomic struct S p)
+{
+  int e = 0 && p.x;
+  return p.x + e; /* { dg-warning "accessing a member .x. of an atomic structure" } */
+}
+
+int
+fn2 (_Atomic struct S *p)
+{
+  int e = 1 || p->x;
+  return p->x + e; /* { dg-warning "accessing a member .x. of an atomic structure" } */
+}
+
+void
+fn3 (_Atomic struct S p, int x)
+{
+  p.x = x; /* { dg-warning "accessing a member .x. of an atomic structure" } */
+}
+
+void
+fn4 (_Atomic struct S *p, int x)
+{
+  p->x = x; /* { dg-warning "accessing a member .x. of an atomic structure" } */
+}
+
+int
+fn5 (_Atomic struct S p)
+{
+  /* This is OK: Members can be safely accessed using a non-atomic
+     object which is assigned to or from the atomic object.  */
+  struct S s = p;
+  return s.x;
+}
+
+int
+fn6 (_Atomic struct S *p)
+{
+  struct S s = *p;
+  return s.x;
+}
+
+int
+fn7 (_Atomic union U p)
+{
+  int e = 0 && p.x;
+  return p.x + e; /* { dg-warning "accessing a member .x. of an atomic union" } */
+}
+
+int
+fn8 (_Atomic union U *p)
+{
+  int e = 1 || p->x;
+  return p->x + e; /* { dg-warning "accessing a member .x. of an atomic union" } */
+}
+
+void
+fn9 (_Atomic union U p, int x)
+{
+  p.x = x; /* { dg-warning "accessing a member .x. of an atomic union" } */
+}
+
+void
+fn10 (_Atomic union U *p, int x)
+{
+  p->x = x; /* { dg-warning "accessing a member .x. of an atomic union" } */
+}
+
+int
+fn11 (_Atomic union U p)
+{
+  /* This is OK: Members can be safely accessed using a non-atomic
+     object which is assigned to or from the atomic object.  */
+  union U s = p;
+  return s.x;
+}
+
+int
+fn12 (_Atomic union U *p)
+{
+  union U s = *p;
+  return s.x;
+}