https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94951
Bug ID: 94951
Summary: dereferencing type-punned pointer will break
strict-aliasing rules when using super class for a
template type
Product: gcc
Version: 9.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: jorgen.lind at gmail dot com
Target Milestone: ---
The following program issues the warning when compiled with -O2 or -O3.
The workaround is to static_cast usage of members to super class.
In the godbolt example its sufficient to add brackets around the class instance
before member access, but was not sufficient in a more complex example.
The behavior is present from 7.1 until trunk.
Godbolt link:https://godbolt.org/z/Kfp-ac
#include <stdint.h>
struct A
{
uint32_t someData[32];
};
template<int N>
struct B : public A
{
static B<N> createB(uint32_t (&otherData)[32])
{
B<N> toReturn;
toReturn.someData[2] = 4;
return toReturn;
}
};
