Merge pull request #8200 from WalterBright/fix15869

fix Issue 15869 - RVO can overwrite argument merged-on-behalf-of: Razvan Nitu <RazvanN7@users.noreply.github.com>
dlang · May 14, 2018 · 68eb9d3 · 68eb9d3
2 parents 21f25f2 + 0ba1f25
commit 68eb9d3
Show file tree

Hide file tree

Showing 3 changed files with 57 additions and 1 deletion.
diff --git a/src/dmd/declaration.d b/src/dmd/declaration.d
@@ -76,7 +76,7 @@ extern (C++) bool checkFrameAccess(Loc loc, Scope* sc, AggregateDeclaration ad,
  * Mark variable v as modified if it is inside a constructor that var
  * is a field in.
  */
-private int modifyFieldVar(Loc loc, Scope* sc, VarDeclaration var, Expression e1)
+bool modifyFieldVar(Loc loc, Scope* sc, VarDeclaration var, Expression e1)
 {
     //printf("modifyFieldVar(var = %s)\n", var.toChars());
     Dsymbol s = sc.func;

diff --git a/src/dmd/expression.d b/src/dmd/expression.d
@@ -26,6 +26,7 @@ import dmd.canthrow;
 import dmd.complex;
 import dmd.constfold;
 import dmd.ctfeexpr;
+import dmd.ctorflow;
 import dmd.dcast;
 import dmd.dclass;
 import dmd.declaration;
@@ -5326,6 +5327,30 @@ extern (C++) final class DotVarExp : UnaExp
     override Expression toLvalue(Scope* sc, Expression e)
     {
         //printf("DotVarExp::toLvalue(%s)\n", toChars());
+        if (e1.op == TOK.this_ && sc.ctorflow.fieldinit.length && !(sc.ctorflow.callSuper & CSX.any_ctor))
+        {
+            if (VarDeclaration vd = var.isVarDeclaration())
+            {
+                auto ad = vd.isMember2();
+                if (ad && ad.fields.dim == sc.ctorflow.fieldinit.length)
+                {
+                    foreach (i, f; ad.fields)
+                    {
+                        if (f == vd)
+                        {
+                            if (!(sc.ctorflow.fieldinit[i] & CSX.this_ctor))
+                            {
+                                /* If the address of vd is taken, assume it is thereby initialized
+                                 * https://issues.dlang.org/show_bug.cgi?id=15869
+                                 */
+                                modifyFieldVar(loc, sc, vd, e1);
+                            }
+                            break;
+                        }
+                    }
+                }
+            }
+        }
         return this;
     }
 

diff --git a/test/runnable/sctor.d b/test/runnable/sctor.d
@@ -415,6 +415,36 @@ void test15665()
     scope foo = new C15665!int;
 }
 
+/***************************************************/
+// https://issues.dlang.org/show_bug.cgi?id=15869
+
+struct Set {
+    @disable this(this);
+    int value = 0;
+}
+
+Set clobber(ref Set a) {
+    Set ret; // <- This overwrites *a, i.e. &ret is the same as a
+    ret.value = a.value; // <- Now a.value is 0
+    return ret;
+}
+
+struct XX {
+    Set a = Set(1);
+    this(int n) {
+        a = clobber(a); // fix is to make this an assignment, not a construction
+    }
+}
+void test15869()
+{
+    Set a = Set(1);
+    a = clobber(a);
+    assert(a.value == 1);
+
+    XX xx = XX(0);
+    assert(xx.a.value == 1);
+}
+
 /***************************************************/
 
 int main()
@@ -426,6 +456,7 @@ int main()
     test14450();
     test14944();
     test15665();
+    test15869();
 
     printf("Success\n");
     return 0;