[PATCH v1 4/7] bfd: fix memory leak when default-initializing an OAv2 attribute

[Jan Beulich]

On 05.02.2026 18:39, Matthieu Longo wrote:
> On 05/02/2026 16:49, Jan Beulich wrote:
>> On 05.02.2026 17:02, Matthieu Longo wrote:
>>> On 05/02/2026 15:39, Jan Beulich wrote:
>>>> On 05.02.2026 16:18, Matthieu Longo wrote:
>>>>> New version using oav2_assign_value().
>>>>
>>>> Just one question:
>>>>
>>>>> --- a/bfd/elf-attrs.c
>>>>> +++ b/bfd/elf-attrs.c
>>>>> @@ -1083,33 +1083,30 @@ oav2_attr_overwrite_with_default (const struct bfd_link_info *info,
>>>>>     {
>>>>>       const struct elf_backend_data *bed = get_elf_backend_data (info->output_bfd);
>>>>>
>>>>> +  union obj_attr_value_v2 default_value;
>>>>> +  memset (&default_value, 0, sizeof (default_value));
>>>>
>>>> Why not via an initializer?
>>>
>>> I did some research because I remember that last time I had to initialize a union with zero, there was an issue somewhere.
>>> And I found that:
>>>
>>>     {0} initializer in C or C++ for unions no longer guarantees clearing of the
>>>     whole union (except for static storage duration initialization), it just
>>>     initializes the first union member to zero. If initialization of the whole
>>>     union including padding bits is desirable, use {} (valid in C23 or C++) or use
>>>     -fzero-init-padding-bits=unions option to restore the old GCC behavior.
>>>
>>>     Source: https://gcc.gnu.org/gcc-15/changes.html
>>>
>>> We don't want to make C23 a requirement. And at the same time, the code must not be broken if someone wants to use C23.
>>> So neither {0} nor {} would work here in my understanding.
>>
>> Correct. But a dedicated initializer should work, aiui, for those being specified
>> to work like static storage duration initializers.
> 
> I am not sure I understood you well.
> Are you saying that I could use the following to initialize the union ?
> union obj_attr_value_v2 default_value = { .int = 0, };
> But this initializes only one member. The string address was only partially initialized to NULL.
> union obj_attr_value_v2 default_value = { .int = 0, .string = NULL }; does not work.
> And union obj_attr_value_v2 default_value = { .string = NULL }; works but it assumes that the biggest element in the union will always be 'const char *'.

With what Andreas has said subsequently, please keep the memset(). I.e.
okay as is.

Jan