Re: Why does -Wabi-tag complain when -std=c++03?

[Jeffrey Walton <noloader at gmail dot com>]

On Thu, Mar 24, 2016 at 8:29 AM, Jonathan Wakely <jwakely.gcc@gmail.com> wrote:
> On 24 March 2016 at 12:20, Jeffrey Walton <noloader@gmail.com> wrote:
>> On Thu, Mar 24, 2016 at 8:10 AM, Jonathan Wakely <jwakely.gcc@gmail.com> wrote:
>>> On 24 March 2016 at 11:55, Jeffrey Walton wrote:
>>>> In the test program below, why does -Wabi-tag trigger a warning with
>>>> the std::string when using -std=c++03?
>>>
>>> "Although the changes were made for C++11 conformance, the choice of
>>> ABI to use is independent of the -std option used to compile your
>>> code, i.e. for a given GCC build the default value of the
>>> _GLIBCXX_USE_CXX11_ABI macro is the same for all dialects. This
>>> ensures that the -std does not change the ABI, so that it is
>>> straightforward to link C++03 and C++11 code together. "
>>>
>>> https://gcc.gnu.org/onlinedocs/libstdc++/manual/using_dual_abi.html
>>
>> Thanks. I recall reading that a couple of days ago. I still don't
>> quite understand what it means. I'm obviously missing something.
>>
>> I guess my knowledge gap is due to _GLIBCXX_USE_CXX11_ABI should apply
>> to C++11 and above to comply with the newer C++ rules, wrote-on-copy
>> strings, etc. I don't understand how it effects C++03 and below since
>> the rules that required the change don't apply.
>
> The new std::string and std::list are also valid implementations for C++03.

OK, good. Thanks.

If its a valid implementation, then why is the compiler complaining?
What, exactly, is the problem or condition that needs fixing?

This is why I was trying to find the GCC 5.1 docs. I needed to read
more about -Wabi-tag. But it appears -Wabi-tag is not documented; cf.,
https://gcc.gnu.org/onlinedocs/gcc-5.1.0/gcc/Warning-Options.html#Warning-Options.

Jeff