diff mbox

C++ PATCH for c++/57926 (atomic builtins and C++ arrays)

Message ID 5348331C.8000805@redhat.com
State New
Headers show

Commit Message

Jason Merrill April 11, 2014, 6:23 p.m. UTC 
In the C front end, arrays used as expressions immediately decay to 
pointers.  In C++, they don't decay until we know that the expression is 
being used as an rvalue, as we might want to bind a reference to the 
array as a whole.  The atomics code in c-common expects pointers, so 
let's force any array arguments to decay.

Tested x86_64-pc-linux-gnu, applying to trunk.
diff mbox

Patch

commit 36cb4ee17f1d0e9fd14210fda1eb43e21637e981
Author: Jason Merrill <jason@redhat.com>
Date:   Mon Apr 7 12:57:34 2014 -0400

    	PR c++/57926
    	* c-common.c (sync_resolve_size, get_atomic_generic_size): Call
    	default_conversion for an array argument.

diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c
index 03731b4..1d56bc0 100644
--- a/gcc/c-family/c-common.c
+++ b/gcc/c-family/c-common.c
@@ -10202,6 +10202,13 @@  sync_resolve_size (tree function, vec<tree, va_gc> *params)
     }
 
   type = TREE_TYPE ((*params)[0]);
+  if (TREE_CODE (type) == ARRAY_TYPE)
+    {
+      /* Force array-to-pointer decay for C++.  */
+      gcc_assert (c_dialect_cxx());
+      (*params)[0] = default_conversion ((*params)[0]);
+      type = TREE_TYPE ((*params)[0]);
+    }
   if (TREE_CODE (type) != POINTER_TYPE)
     goto incompatible;
 
@@ -10353,6 +10360,13 @@  get_atomic_generic_size (location_t loc, tree function,
 
   /* Get type of first parameter, and determine its size.  */
   type_0 = TREE_TYPE ((*params)[0]);
+  if (TREE_CODE (type_0) == ARRAY_TYPE)
+    {
+      /* Force array-to-pointer decay for C++.  */
+      gcc_assert (c_dialect_cxx());
+      (*params)[0] = default_conversion ((*params)[0]);
+      type_0 = TREE_TYPE ((*params)[0]);
+    }
   if (TREE_CODE (type_0) != POINTER_TYPE || VOID_TYPE_P (TREE_TYPE (type_0)))
     {
       error_at (loc, "argument 1 of %qE must be a non-void pointer type",
diff --git a/gcc/testsuite/g++.dg/ext/atomic-2.C b/gcc/testsuite/g++.dg/ext/atomic-2.C
new file mode 100644
index 0000000..ac363eb
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/atomic-2.C
@@ -0,0 +1,14 @@ 
+// PR c++/57926
+
+long Mutex[1];
+
+int AcquireLogMutex(void)
+{
+  return __atomic_exchange_n(Mutex, 1, __ATOMIC_SEQ_CST);
+}
+
+void ReleaseLogMutex(void)
+{
+  long i = 0;
+  __atomic_store(Mutex, &i, __ATOMIC_SEQ_CST);
+}