Re: gcc generated memcpy calls symbol version

[Tom Mason <wheybags at wheybags dot com>]

Actually, never mind, it's working fine:
https://gist.github.com/wheybags/b7e4152daf76c72503e9e1f52f3dca3d and I
have some other problem.


On Fri, Jan 26, 2018 at 9:22 PM, H.J. Lu <hjl.tools@gmail.com> wrote:

> On Fri, Jan 26, 2018 at 1:17 PM, Tom Mason <wheybags@wheybags.com> wrote:
> > I'm not entirely sure I understand that issue. From what I understand,
> calls
> > to a function in a shared library should always use the PLT?
> > Also, I don't understand the purpose of applying hidden visibility to an
> > extern symbol,
>
> There is no need for PLT since hidden symbol is defined locally.  But
> GCC ignores hidden visibility for libcalls, like memcpy.  If GCC treats
> them like normal calls, your scheme and my testcase should work.
>
>
> > But anyway, doesn't matter terribly much if I understand :p
> >
> > On Fri, Jan 26, 2018 at 8:37 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
> >>
> >> On Fri, Jan 26, 2018 at 12:29 PM, Tom Mason <wheybags@wheybags.com>
> wrote:
> >> > Hi,
> >> > I've got a project here:
> >> > https://github.com/wheybags/glibc_version_header
> >> > which uses .symver directives to link to a specified version of glibc,
> >> > so
> >> > long as it's older than the version on your system.
> >> > This works, but a problem I'm having is that gcc itself will sometimes
> >> > insert calls to memcpy (or memmove, memset and memcmp), as documented
> >> > here:
> >> > https://gcc.gnu.org/onlinedocs/gcc/Standards.html
> >> > When it does so, it doesn't respect the .symver directives, and uses
> the
> >> > default version.
> >> > Is there any way for me to force the version for these symbols aswell?
> >> > I'm aware that I can disable the whole mechanism with -freestanding,
> but
> >> > I
> >> > don't want to cripple the optimiser.
> >>
> >> I think this is related to:
> >>
> >> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67220
> >>
> >> --
> >> H.J.
> >
> >
>
>
>
> --
> H.J.
>