Re: Linking to dynamic libraries compiled by old version g++

[孙世龙 <sunshilong369@gmail.com>]

> Specifically, there were changes to std::chrono::system_clock, and
>std::error_category, and std::condition_variable.
>If those types are used in the old dynamic libraries, particularly
>across the library API boundary, then you are likely to run into problems.
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

If the aforementioned types are only used in the implementation of the library
which is compiled with 4.9.4 and the interface of the library is a C
interface.

If I understand you correctly, there is no potential problem if a binary program
is compiled with g++11.0.3 and is linked to the said library. Am I right?

Best regards

On Mon, Nov 7, 2022 at 9:02 PM Jonathan Wakely <jwakely.gcc@gmail.com> wrote:
>
> On Mon, 7 Nov 2022 at 02:11, 孙世龙 via Gcc-help <gcc-help@gcc.gnu.org> wrote:
> >
> > There are dynamic libraries provided by others, which are out of my control.
> >
> > What I know is that most of the aforementioned libraries are compiled
> > by g++4.9.4 & g++4.8.4 with C++11 support, and some libraries are
> > compiled by g++11.1.0 with C++14 support.
> >
> > And I have to use newer g++ which supports C++17 to compile my
> > project. I intend to use g++11.3.0 on Ubuntu20.4.
> >
> > Is there any potential problem I should be aware of when linking to
> > dynamic libraries compiled by the said old version g++ ?
>
> Yes, this is not supported.
>
> C++11 support in GCC 4.8 and 4.9 was experimental and unstable, and is
> not ABI compatible with C++11 code compiled by GCC 5 or later.
>
> Specifically, there were changes to std::chrono::system_clock, and
> std::error_category, and std::condition_variable. If those types are
> used in the old dynamic libraries, particularly across the library API
> boundary, then you are likely to run into problems. There are probably
> other incompatibilities that I'm forgetting. I don't bother to
> remember all the incompatibilities, because what you're trying to do
> is not supported and so I don't spend any effort memorising all the
> ways it can fail.