Re: Extra import symbol in debug build

[Jonathan Wakely <jwakely.gcc@gmail.com>]

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On Fri, 17 Feb 2023, 08:51 , <i.nixman@autistici.org> wrote:

> On 2023-02-16 20:08, Jonathan Wakely wrote:
> > On Thu, 16 Feb 2023, 18:39 , <i.nixman@autistici.org> wrote:
> >
> >> On 2023-02-16 15:29, Jonathan Wakely wrote:
> >> > On Thu, 16 Feb 2023 at 15:25, i.nixman--- via Gcc-help
> >> > <gcc-help@gcc.gnu.org> wrote:
> >> >>
> >> >> hello,
> >> >>
> >> >>
> >> >> I can successfully build the same C++ code using GCC-8.3.1 for Debug
> >> >> (-g
> >> >> -O0) and Release (-g -O2) build.
> >> >> I can successfully debug the Release-executable on a remote host, but
> >> >> I
> >> >> can't debug the Debug-executable on a remote host, because the
> >> >> Debug-executable imports an extra symbol
> >> >> _ZNKSt9basic_iosIcSt11char_traitsIcEEcvbEv from libstdc++ which
> >> >> doesn't
> >> >> exist.
> >> >
> >> > It should exist, it has been there since GCC
> >>
> >> hmm...
> >>
> >> I just checked the two binaries using this cmd:
> >>
> >> > readelf -sW executable | grep
> >> > _ZNKSt9basic_iosIcSt11char_traitsIcEEcvbEv
> >>
> >> it shows nothing for release build, and shows this for debug build:
> >>
> >> >     54: 0000000000000000     0 FUNC    GLOBAL DEFAULT  UND
> >> > _ZNKSt9basic_iosIcSt11char_traitsIcEEcvbEv
> >> > 199898: 0000000000000000     0 FUNC    GLOBAL DEFAULT  UND
> >> > _ZNKSt9basic_iosIcSt11char_traitsIcEEcvbEv
> >>
> >
> >
> > This only shows that the function is inlined in the optimized build,
> > and
> > not in the debug build, so the debug one has an unresolved reference to
> > a
> > symbol defined in the libstdc++ dynamic library. This is completely
> > normal.
> >
>
> then I have two questions:
>
> 1. will the problem be solved by "pushing" a debug version of libstdc++
> on the remote machine?
>

You don't need a debug version, the symbol is present in all builds of
libstdc++.



> 2. how can I define this symbol in the project code for debug build to
> avoid having to use the debug version of libstdc++?
> something like this? :
> namespace std {
>     template basic_ios<char, char_traits<char> >::operator bool() const;
> }
>
>
>
>
> best!
>