Re: [Gimp-developer] gcc-7 vs gcc-6

[Ken Moffat <zarniwhoop ntlworld com>]

On Fri, Nov 10, 2017 at 04:52:43PM -0500, Elle Stone wrote:
> On 11/10/2017 02:42 PM, Carol Spears wrote:
> > After a couple of catastrophes, I reinstalled my operating system ... and
> > eventually rebuilt gimp.
> >
> > The gcc-7 gimp failed to open with a
> >     gimp: symbol lookup error: gimp: undefined symbol:
> > gimp_convert_dither_type_compat_get_type
> >
> > The gcc-6 gimp works fine.
> >
> > Were my problems related to gcc-7?
>
> In case it might be relevant, this bug indicates a problem specifically with
> gcc-7.2:
>
> https://bugzilla.gnome.org/show_bug.cgi?id=787222#c5
>
> Best,
> Elle
I can't comment on that specific bug (I haven't converted anything
to 16-bit float), but I've used gcc-7.2.0 to build both 2.9.6 and
2.8.22 on different machines without any problems (both using
gegl-0.3.20, 2.8.22 modified as in BLFS to do that) and both appear
to work, they certainly start OK.

My impression of symbol lookup errors (after a quick google) is that
they are caused by mismatched versions of libraries.

In one thread at an opensuse forum (for that same symbol)  the
problem was apparently caused by getting binaries from a differnt
repo, and soembody had to also get libgimp (they separate it!),
lcms, babl, and gegl from the other repo.

But if by 'rebuilding' Carol meant "recompiled on the same machine"
I have no idea.  Her post implies that both gcc-6 and gcc-7 versions
are on the same machine, which seems an uncommon approach (assuming
both are the same version and this isn't just to test for gcc
regressions).

But I haven't tried building applications with a newer version of
gcc on a system built with an older gcc for many years, perhaps I'm
overlooking something (e.g. changed calling conventions in the newer
C++ standard).

Looking at my 2.9 version, the symbol is in both libgimp-2.0.so and
libgimpbase-2.0.so, but not in any of the modules.  So I suppose the
way in is to use ldd to look at what those libs link to (and to
check that the gcc-7 versions are being used).

ĸen
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