From: Jakub Jelinek <jakub@redhat.com>
Date: Tue, 30 May 2017 08:17:18 +0000 (+0200)
Subject: backport: re PR c++/80129 (wrong code with ternary struct assignment to const)
X-Git-Tag: releases/gcc-5.5.0~251
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=108358c7692648b5d4b84ed0877504a208bf5034;p=thirdparty%2Fgcc.git

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

	Backported from mainline
	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.

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

From-SVN: r248662
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 09a6a4bf9f74..5ec64f66e44d 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,6 +1,12 @@
 2017-05-30  Jakub Jelinek  <jakub@redhat.com>
 
 	Backported from mainline
+	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.
+
 	2017-03-09  Jakub Jelinek  <jakub@redhat.com>
 
 	PR sanitizer/79944
diff --git a/gcc/gimplify.c b/gcc/gimplify.c
index b7aa11d67fcd..052fc08aba77 100644
--- a/gcc/gimplify.c
+++ b/gcc/gimplify.c
@@ -4293,6 +4293,14 @@ 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 7f1612091ef3..895f61037d20 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,6 +1,11 @@
 2017-05-30  Jakub Jelinek  <jakub@redhat.com>
 
 	Backported from mainline
+	2017-03-22  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/80129
+	* g++.dg/torture/pr80129.C: New test.
+
 	2017-03-21  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c/80097
diff --git a/gcc/testsuite/g++.dg/torture/pr80129.C b/gcc/testsuite/g++.dg/torture/pr80129.C
new file mode 100644
index 000000000000..134293cd0855
--- /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 ();
+}