From: Jakub Jelinek <jakub@redhat.com>
Date: Wed, 22 Mar 2017 18:45:48 +0000 (+0100)
Subject: re PR c++/80129 (wrong code with ternary struct assignment to const)
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=68ed2ba0a7d60275ac044a4cb50b33eb33fbb813;p=gcc.git

re PR c++/80129 (wrong code with ternary struct assignment to const)

	PR c++/80129
	* gimplify.c (gimplify_modify_expr_rhs) <case COND_EXPR>: Clear
	TREE_READONLY on result if writing it more than once.

	* g++.dg/torture/pr80129.C: New test.

From-SVN: r246401
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index a1e007f118d..5259dce80a5 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,9 @@
 2017-03-22  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c++/80129
+	* gimplify.c (gimplify_modify_expr_rhs) <case COND_EXPR>: Clear
+	TREE_READONLY on result if writing it more than once.
+
 	PR sanitizer/80110
 	* doc/invoke.texi (-fsanitize=thread): Document that with
 	-fnon-call-exceptions atomics are not able to throw
diff --git a/gcc/gimplify.c b/gcc/gimplify.c
index 5658d0a2f0b..f90ae94bc69 100644
--- a/gcc/gimplify.c
+++ b/gcc/gimplify.c
@@ -5098,6 +5098,14 @@ gimplify_modify_expr_rhs (tree *expr_p, tree *from_p, tree *to_p,
 	      if (ret != GS_ERROR)
 		ret = GS_OK;
 
+	      /* If we are going to write RESULT more than once, clear
+		 TREE_READONLY flag, otherwise we might incorrectly promote
+		 the variable to static const and initialize it at compile
+		 time in one of the branches.  */
+	      if (VAR_P (result)
+		  && TREE_TYPE (TREE_OPERAND (cond, 1)) != void_type_node
+		  && TREE_TYPE (TREE_OPERAND (cond, 2)) != void_type_node)
+		TREE_READONLY (result) = 0;
 	      if (TREE_TYPE (TREE_OPERAND (cond, 1)) != void_type_node)
 		TREE_OPERAND (cond, 1)
 		  = build2 (code, void_type_node, result,
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index d8b45dcacf6..add3a14eca5 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,5 +1,8 @@
 2017-03-22  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c++/80129
+	* g++.dg/torture/pr80129.C: New test.
+
 	PR sanitizer/80110
 	* g++.dg/tsan/pr80110.C: New test.
 
diff --git a/gcc/testsuite/g++.dg/torture/pr80129.C b/gcc/testsuite/g++.dg/torture/pr80129.C
new file mode 100644
index 00000000000..134293cd085
--- /dev/null
+++ b/gcc/testsuite/g++.dg/torture/pr80129.C
@@ -0,0 +1,14 @@
+// PR c++/80129
+// { dg-do run }
+// { dg-options "-std=c++11" }
+
+struct A { bool a; int b; };
+
+int
+main ()
+{
+  bool c = false;
+  const A x = c ? A {true, 1} : A {false, 0};
+  if (x.a)
+    __builtin_abort ();
+}