From 798bdfa0ebcf2bd012ffce75a594f783a8cb2dd0 Mon Sep 17 00:00:00 2001
From: Iain Buclaw <ibuclaw@gdcproject.org>
Date: Tue, 17 Nov 2020 13:11:33 +0100
Subject: [PATCH] d: Fix LHS of array concatentation evaluated before the RHS.

In an array append expression:

    array ~= fun(array);

The array in the left hand side of the expression was extended before
evaluating the result of the right hand side, which resulted in the
newly uninitialized array index being used before set.

This fixes that so that the result of the right hand side is always
saved in a reusable temporary before assigning to the destination.

gcc/d/ChangeLog:

	PR d/97843
	* d-codegen.cc (build_assign): Evaluate TARGET_EXPR before use in
	the right hand side of an assignment.
	* expr.cc (ExprVisitor::visit (CatAssignExp *)): Force a TARGET_EXPR
	on the element to append if it is a CALL_EXPR.

gcc/testsuite/ChangeLog:

	PR d/97843
	* gdc.dg/torture/pr97843.d: New test.
---
 gcc/d/d-codegen.cc                     |  5 +++-
 gcc/d/expr.cc                          |  3 +++
 gcc/testsuite/gdc.dg/torture/pr97843.d | 37 ++++++++++++++++++++++++++
 3 files changed, 44 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gdc.dg/torture/pr97843.d

diff --git a/gcc/d/d-codegen.cc b/gcc/d/d-codegen.cc
index 1f2d65c4ae2..4c16f6a822b 100644
--- a/gcc/d/d-codegen.cc
+++ b/gcc/d/d-codegen.cc
@@ -1343,7 +1343,10 @@ build_assign (tree_code code, tree lhs, tree rhs)
 	 since that would cause the LHS to be constructed twice.
 	 So we force the TARGET_EXPR to be expanded without a target.  */
       if (code != INIT_EXPR)
-	rhs = compound_expr (rhs, TARGET_EXPR_SLOT (rhs));
+	{
+	  init = compound_expr (init, rhs);
+	  rhs = TARGET_EXPR_SLOT (rhs);
+	}
       else
 	{
 	  d_mark_addressable (lhs);
diff --git a/gcc/d/expr.cc b/gcc/d/expr.cc
index 79f212c3a08..ef2bf5f2e36 100644
--- a/gcc/d/expr.cc
+++ b/gcc/d/expr.cc
@@ -884,6 +884,9 @@ public:
 	    tree t2 = build_expr (e->e2);
 	    tree expr = stabilize_expr (&t2);
 
+	    if (TREE_CODE (t2) == CALL_EXPR)
+	      t2 = force_target_expr (t2);
+
 	    result = modify_expr (build_deref (ptrexp), t2);
 
 	    this->result_ = compound_expr (expr, result);
diff --git a/gcc/testsuite/gdc.dg/torture/pr97843.d b/gcc/testsuite/gdc.dg/torture/pr97843.d
new file mode 100644
index 00000000000..1a417b32359
--- /dev/null
+++ b/gcc/testsuite/gdc.dg/torture/pr97843.d
@@ -0,0 +1,37 @@
+// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97843
+// { dg-additional-options "-fmain -funittest" }
+// { dg-do run }
+// { dg-skip-if "needs gcc/config.d" { ! d_runtime } }
+
+struct Sdtor
+{
+    int value;
+    ~this() { }
+}
+
+Sdtor sum(Sdtor[] sdtors)
+{
+    int result;
+    foreach (s; sdtors)
+        result += s.value;
+    return Sdtor(result);
+}
+
+uint sum(uint[] ints)
+{
+    uint result;
+    foreach(i; ints)
+        result += i;
+    return result;
+}
+
+unittest
+{
+    Sdtor[] sdtors = [Sdtor(0), Sdtor(1)];
+    sdtors ~= sum(sdtors);
+    assert(sdtors == [Sdtor(0), Sdtor(1), Sdtor(1)]);
+
+    uint[] ints = [0, 1];
+    ints ~= ints.sum;
+    assert(ints == [0, 1, 1]);
+}
-- 
2.30.2