While looking at guaranteed copy elision, I noticed some outstanding
issues with temporary lifetime extension. In one case, we were
failing to extend temporaries bound to references within another
temporary. In another, we were failing to extend a temporary when we
bind a reference to a scalar subobject.
Tested x86_64-pc-linux-gnu, applying to trunk.
commit 72052afef06d077e8061b974aff3c2910037b7a0
Author: Jason Merrill <ja...@redhat.com>
Date: Wed Oct 5 14:30:18 2016 -0400
* call.c (extend_ref_init_temps): Fix TARGET_EXPR handling.
diff --git a/gcc/cp/call.c b/gcc/cp/call.c
index 0914ae2..c333418 100644
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -10172,28 +10172,31 @@ extend_ref_init_temps (tree decl, tree init,
vec<tree, va_gc> **cleanups)
return init;
if (TREE_CODE (type) == REFERENCE_TYPE)
init = extend_ref_init_temps_1 (decl, init, cleanups);
- else if (is_std_init_list (type))
+ else
{
- /* The temporary array underlying a std::initializer_list
- is handled like a reference temporary. */
tree ctor = init;
if (TREE_CODE (ctor) == TARGET_EXPR)
ctor = TARGET_EXPR_INITIAL (ctor);
if (TREE_CODE (ctor) == CONSTRUCTOR)
{
- tree array = CONSTRUCTOR_ELT (ctor, 0)->value;
- array = extend_ref_init_temps_1 (decl, array, cleanups);
- CONSTRUCTOR_ELT (ctor, 0)->value = array;
+ if (is_std_init_list (type))
+ {
+ /* The temporary array underlying a std::initializer_list
+ is handled like a reference temporary. */
+ tree array = CONSTRUCTOR_ELT (ctor, 0)->value;
+ array = extend_ref_init_temps_1 (decl, array, cleanups);
+ CONSTRUCTOR_ELT (ctor, 0)->value = array;
+ }
+ else
+ {
+ unsigned i;
+ constructor_elt *p;
+ vec<constructor_elt, va_gc> *elts = CONSTRUCTOR_ELTS (ctor);
+ FOR_EACH_VEC_SAFE_ELT (elts, i, p)
+ p->value = extend_ref_init_temps (decl, p->value, cleanups);
+ }
}
}
- else if (TREE_CODE (init) == CONSTRUCTOR)
- {
- unsigned i;
- constructor_elt *p;
- vec<constructor_elt, va_gc> *elts = CONSTRUCTOR_ELTS (init);
- FOR_EACH_VEC_SAFE_ELT (elts, i, p)
- p->value = extend_ref_init_temps (decl, p->value, cleanups);
- }
return init;
}
diff --git a/gcc/testsuite/g++.dg/cpp1z/elide2.C
b/gcc/testsuite/g++.dg/cpp1z/elide2.C
new file mode 100644
index 0000000..277decf
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/elide2.C
@@ -0,0 +1,25 @@
+// DR 1697
+// { dg-do run { target c++11 } }
+
+#define assert(X) do { if (!(X)) __builtin_abort(); } while(0)
+
+int i;
+struct S {
+ ~S() { assert (i++ == 2); }
+};
+struct X {
+ X() { assert (i++ == 0); }
+ X(const X&);
+};
+struct T {
+ S &&s;
+ X x;
+};
+void f() { assert (i++ == 1); }
+int main() {
+ {
+ T t = T{ {}, {} };
+ f();
+ }
+ assert (i == 3);
+}
commit c9d1d33ded916cb7f0dbbf6b7b4673acc2af0244
Author: Jason Merrill <ja...@redhat.com>
Date: Wed Oct 5 16:24:33 2016 -0400
PR c++/54293 - binding reference to member of temporary
* call.c (reference_binding): Fix binding to member of temporary.
diff --git a/gcc/cp/call.c b/gcc/cp/call.c
index c333418..dac1337 100644
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -1539,15 +1539,20 @@ reference_binding (tree rto, tree rfrom, tree expr,
bool c_cast_p, int flags,
gl_kind = clk_rvalueref;
}
else if (expr)
- {
- gl_kind = lvalue_kind (expr);
- if (gl_kind & clk_class)
- /* A class prvalue is not a glvalue. */
- gl_kind = clk_none;
- }
+ gl_kind = lvalue_kind (expr);
+ else if (CLASS_TYPE_P (from)
+ || TREE_CODE (from) == ARRAY_TYPE)
+ gl_kind = clk_class;
else
gl_kind = clk_none;
- is_lvalue = gl_kind && !(gl_kind & clk_rvalueref);
+
+ /* Don't allow a class prvalue when LOOKUP_NO_TEMP_BIND. */
+ if ((flags & LOOKUP_NO_TEMP_BIND)
+ && (gl_kind & clk_class))
+ gl_kind = clk_none;
+
+ /* Same mask as real_lvalue_p. */
+ is_lvalue = gl_kind && !(gl_kind & (clk_rvalueref|clk_class));
tfrom = from;
if ((gl_kind & clk_bitfield) != 0)
@@ -1569,11 +1574,7 @@ reference_binding (tree rto, tree rfrom, tree expr, bool
c_cast_p, int flags,
[8.5.3/5 dcl.init.ref] is changed to also require direct bindings for
const and rvalue references to rvalues of compatible class type.
We should also do direct bindings for non-class xvalues. */
- if (related_p
- && (gl_kind
- || (!(flags & LOOKUP_NO_TEMP_BIND)
- && (CLASS_TYPE_P (from)
- || TREE_CODE (from) == ARRAY_TYPE))))
+ if (related_p && gl_kind)
{
/* [dcl.init.ref]
diff --git a/gcc/testsuite/g++.dg/init/ref19.C
b/gcc/testsuite/g++.dg/init/ref19.C
index ed78c93..d583e93 100644
--- a/gcc/testsuite/g++.dg/init/ref19.C
+++ b/gcc/testsuite/g++.dg/init/ref19.C
@@ -11,7 +11,11 @@ struct A
int main()
{
- const int &r = A().i;
+ {
+ const int &r = A().i;
+ if (d != 0)
+ return 1;
+ }
if (d != 1)
return 1;
}
