Re: [PATCH] Link to -lssp when available (fixes mingw build)

Christian Biesinger via gdb-patches
2019-12-19T20:41:15Z

On Thu, Dec 19, 2019 at 8:19 AM Pedro Alves <palves@redhat.com> wrote:
>
> On 12/18/19 11:23 PM, Christian Biesinger via gdb-patches wrote:
> > On Wed, Dec 18, 2019 at 5:12 PM Eli Zaretskii <eliz@gnu.org> wrote:
> >>
> >>> From: "Christian Biesinger via gdb-patches" <gdb-patches@sourceware.org>
> >>> Date: Wed, 18 Dec 2019 14:40:42 -0600
> >>> Cc: gdb-patches <gdb-patches@sourceware.org>a lot of
> >>>
> >>> BTW -- you mentioned a licensing issue with depending on DLLs. Doesn't
> >>> libstdc++ and perhaps others have the same issue? Or does mingw.org
> >>> link it statically?
> >>
> >> libstdc++ and libgcc DLLs indeed have the same problem. Which is why
> >> I mentioned the fact that the binary of GDB 9.0.90 produced by the
> >> MinGW build had dependencies on these two. I solved that locally by
> >> linking with "CXX='g++ -static-libstdc++ -static-libgcc'", but I
> >> thought Pedro once said these dependencies shouldn't happen, and I
> >> still hope we could understand why they suddenly appeared.
> >
> > Hm, I wonder why Pedro said that. GDB uses good amounts of the C++
> > standard library, so I would totally expect libstdc++ to appear.
>
> There's some confusion going on here. We must certainly link with
> libstdc++ somehow. The only question is whether we link to the
> dynamic or static version. What I've said in the past is that GDB
> inherited the -static-libstdc++ and -static-libgcc from GCC, due to
> the shared top level configure:
>
> https://sourceware.org/ml/gdb-patches/2019-07/msg00040.html
>
> Linking with static versions of the runtime is problematic if we also link
> with some other library that is itself linked with a different libstdc++.
> Multiple versions of libstc++/libgcc in a program is a recipe for disaster,
> such as for example C++ exceptions not working properly. Discussions about
> this started a few years ago when we switched to C++. E.g.:
>
> https://sourceware.org/ml/gdb-patches/2017-02/msg00705.html
>
> That is why the top level configure was recently changed to avoid the
> -static-libstc++/-static-libgcc:
>
> https://gcc.gnu.org/ml/gcc-patches/2019-08/msg00287.html
>
> Note that the patch added a new --with-static-standard-libraries
> configure switch which you can use to get back the previous behavior
> of linking with the static versions of the standard libraries.
>
> I think a NEWS entry for that switch would be helpful, though.
>
> > I don't really know what libgcc is used for.
>
> libgcc is GCC's low-level runtime library. It's an essential part
> of any program compiled by GCC:
> https://gcc.gnu.org/onlinedocs/gccint/Libgcc.html

Thanks for the detailed explanation!

Christian