When an object is value-initialized, if the type doesn't have a
user-provided default constructor, the object is zero-initialized first,
and then the synthesized constructor is called. The problem in this PR
was that when value-initializing a base in a constructor we were
zero-initializing virtual bases of that base even though they had
already been initialized properly. The fix is to specify to
build_zero_init_1 that we only want to clear the as-base portion of the
type.
On the trunk I also tidied up the logic; on release branches I made the
minimal change. For the 4.4 branch I also needed to backport the fix
for 48035.
Tested x86_64-pc-linux-gnu, applying to 4.4, 4.5, 4.6 and trunk.
commit ae7159a0bd2822557c503cd85d911e0390aaf55d
Author: Jason Merrill <ja...@redhat.com>
Date: Thu Oct 13 12:59:31 2011 -0400
PR c++/50618
* init.c (expand_aggr_init_1): Don't zero-initialize virtual
bases of a base subobject.
diff --git a/gcc/cp/init.c b/gcc/cp/init.c
index 7897fff..8a5bece 100644
--- a/gcc/cp/init.c
+++ b/gcc/cp/init.c
@@ -1588,27 +1588,26 @@ expand_aggr_init_1 (tree binfo, tree true_exp, tree exp, tree init, int flags,
that's value-initialization. */
if (init == void_type_node)
{
- /* If there's a user-provided constructor, we just call that. */
- if (type_has_user_provided_constructor (type))
- /* Fall through. */;
- /* If there isn't, but we still need to call the constructor,
- zero out the object first. */
- else if (type_build_ctor_call (type))
+ /* If no user-provided ctor, we need to zero out the object. */
+ if (!type_has_user_provided_constructor (type))
{
- init = build_zero_init (type, NULL_TREE, /*static_storage_p=*/false);
+ tree field_size = NULL_TREE;
+ if (exp != true_exp
+ && CLASSTYPE_AS_BASE (type) != type)
+ /* Don't clobber already initialized virtual bases. */
+ field_size = TYPE_SIZE (CLASSTYPE_AS_BASE (type));
+ init = build_zero_init_1 (type, NULL_TREE, /*static_storage_p=*/false,
+ field_size);
init = build2 (INIT_EXPR, type, exp, init);
finish_expr_stmt (init);
- /* And then call the constructor. */
}
+
/* If we don't need to mess with the constructor at all,
- then just zero out the object and we're done. */
- else
- {
- init = build2 (INIT_EXPR, type, exp,
- build_value_init_noctor (type, complain));
- finish_expr_stmt (init);
- return;
- }
+ then we're done. */
+ if (! type_build_ctor_call (type))
+ return;
+
+ /* Otherwise fall through and call the constructor. */
init = NULL_TREE;
}
diff --git a/gcc/testsuite/g++.dg/init/vbase1.C b/gcc/testsuite/g++.dg/init/vbase1.C
new file mode 100644
index 0000000..bbfd58f
--- /dev/null
+++ b/gcc/testsuite/g++.dg/init/vbase1.C
@@ -0,0 +1,39 @@
+// PR c++/50618
+// { dg-do run }
+
+struct Base
+{
+ const int text;
+ Base():text(1) {}
+ Base(int aText)
+ : text(aText) {}
+};
+struct SubA : public virtual Base
+{
+protected:
+ int x;
+public:
+ SubA(int aX)
+ : x(aX) {}
+};
+class SubB : public virtual Base
+{};
+struct Diamond : public SubA, public SubB
+{
+ Diamond(int text)
+ : Base(text), SubA(5), SubB() {}
+
+ void printText()
+ {
+ if(text != 2)
+ __builtin_abort();
+ if(x!=5)
+ __builtin_abort();
+ }
+};
+
+int main(int, char**)
+{
+ Diamond x(2);
+ x.printText();
+}
commit fda61bbc8fd29b1df3dbeb576e0dcf806b2fcdf5
Author: Jason Merrill <ja...@redhat.com>
Date: Thu Oct 13 13:11:31 2011 -0400
PR c++/50618
* init.c (expand_aggr_init_1): Don't zero-initialize virtual
bases of a base subobject.
diff --git a/gcc/cp/init.c b/gcc/cp/init.c
index c4bd635..f85a30b 100644
--- a/gcc/cp/init.c
+++ b/gcc/cp/init.c
@@ -1561,7 +1561,12 @@ expand_aggr_init_1 (tree binfo, tree true_exp, tree exp, tree init, int flags,
zero out the object first. */
else if (TYPE_NEEDS_CONSTRUCTING (type))
{
- init = build_zero_init (type, NULL_TREE, /*static_storage_p=*/false);
+ tree field_size = NULL_TREE;
+ if (exp != true_exp && CLASSTYPE_AS_BASE (type) != type)
+ /* Don't clobber already initialized virtual bases. */
+ field_size = TYPE_SIZE (CLASSTYPE_AS_BASE (type));
+ init = build_zero_init_1 (type, NULL_TREE, /*static_storage_p=*/false,
+ field_size);
init = build2 (INIT_EXPR, type, exp, init);
finish_expr_stmt (init);
/* And then call the constructor. */
diff --git a/gcc/testsuite/g++.dg/init/vbase1.C b/gcc/testsuite/g++.dg/init/vbase1.C
new file mode 100644
index 0000000..bbfd58f
--- /dev/null
+++ b/gcc/testsuite/g++.dg/init/vbase1.C
@@ -0,0 +1,39 @@
+// PR c++/50618
+// { dg-do run }
+
+struct Base
+{
+ const int text;
+ Base():text(1) {}
+ Base(int aText)
+ : text(aText) {}
+};
+struct SubA : public virtual Base
+{
+protected:
+ int x;
+public:
+ SubA(int aX)
+ : x(aX) {}
+};
+class SubB : public virtual Base
+{};
+struct Diamond : public SubA, public SubB
+{
+ Diamond(int text)
+ : Base(text), SubA(5), SubB() {}
+
+ void printText()
+ {
+ if(text != 2)
+ __builtin_abort();
+ if(x!=5)
+ __builtin_abort();
+ }
+};
+
+int main(int, char**)
+{
+ Diamond x(2);
+ x.printText();
+}
