struct Base {
Base();
int i;
char c;
};
template <typename BaseT>
struct actor : public BaseT {
actor(BaseT const& base);
char c;
};
template <typename BaseT>
actor<BaseT>::actor(BaseT const& base)
: BaseT(base) {}
actor<Base>
foo(const Base c)
{
return actor<Base>(c);
}
with -O2 we inline the constructor and get
actor<Base> foo(Base) D.2099 (const struct Base c)
{
struct actor D.2133;
struct actor D.2134;
<bb 2>:
D.2133.D.2111 = c;
D.2134 = D.2133;
return D.2134;
}
The assignment
D.2133.D.2111 = c;
has on the LHS a size of 40 (from the FIELD_DECL) and on the
RHS a size of 64, from the decl. In the un-inlined constructor we had
the bogus
actor<BaseT>::actor(const BaseT&) [with BaseT = Base] D.2105 (struct
actor * const this, const struct Base & base)
{
<bb 2>:
this_1(D)->D.2111 = *base_2(D);
return;
}
with the same issue (size 40 on the lhs, size 64 on the rhs).
"Size" in term of what the FIELD_DECL DECL_SIZE says for the component-refs,
which is according to people what is relevant - not the type size. Likewise
for the RHS the DECL_SIZE (which is equal to TYPE_SIZE).
For less contrived examples the FE generates a memcpy to carefully _not_
overwrite padding that may be used in tail packing.
Eventually from the above you can construct a wrong-code testcase if expansion
chooses the wrong size for the expansion of the assignment.
--
Summary: C++ FE generates struct assignments with mismatched
sizes
Product: gcc
Version: 4.5.0
Status: UNCONFIRMED
Keywords: wrong-code
Severity: normal
Priority: P3
Component: c++
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: rguenth at gcc dot gnu dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40058
