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Re: Why does -Wabi-tag complain when -std=c++03?
- From: Jeffrey Walton <noloader at gmail dot com>
- To: Jonathan Wakely <jwakely dot gcc at gmail dot com>
- Cc: "gcc-help at gcc dot gnu dot org" <gcc-help at gcc dot gnu dot org>
- Date: Thu, 24 Mar 2016 08:20:31 -0400
- Subject: Re: Why does -Wabi-tag complain when -std=c++03?
- Authentication-results: sourceware.org; auth=none
- References: <CAH8yC8kYCmJqN4E5s9KQP1sH+PdV0axg9GuEf8MPeMQs0ede_w at mail dot gmail dot com> <CAH6eHdQYuMxhEJFD_P7GD1UgTy+oL4d_To9zwY8SJ1VRAD7J=w at mail dot gmail dot com>
- Reply-to: noloader at gmail dot com
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.
Jeff