--gc-sections and GDC

[Johannes Pfau via D.gnu]

Am Wed, 16 Jul 2014 15:35:09 +0100
schrieb "Iain Buclaw via D.gnu" <d.gnu at puremagic.com>:

> On 16 July 2014 15:12, Mike via D.gnu <d.gnu at puremagic.com> wrote:
> > On Wednesday, 16 July 2014 at 13:52:57 UTC, Mike wrote:
> >>
> >> I received a question from Dicebot in at the end of my
> >> presentation.  He asked about the --gc-sections linker flag
> >> breaking code from GDC.
> >>
> >> I recently discovered how one can see why this is occurring, and I
> >> hope this will help identify the problem and lead to a solution.
> >>
> >> Compile any simple hello world program with the following gcc
> >> command: gcc --verbose -Wl,--verbose test.c.
> >>
> >> Part of the output is GCC's internal linker script as shown
> >> below.  I believe this is the source of the problem.  Here's my
> >> theory.
> >>
> >> D is not C, and is likely generating code that the GCC internal
> >> linker script doesn't know about.  This code may be incorrectly
> >> identified as dead code because there is no 'link' to it and,
> >> therefore, appears unused.  If D or GDC is generating any code
> >> like this, it needs to be marked as KEEP in the linker script.
> >> You can see examples of this in GCC's internal linker script below.
> >>
> >> If my theory is correct, GDC may have to make an internal linker
> >> script specifically for D's code generation that marks such code
> >> as KEEP.
> >>
> >> I hope I'm not just blowing smoke.
> >>
> >> Mike
> >
> >
> > And I just checked with GDC...
> > gdc --verbose -Wl,--verbose test.d
> >
> > ... and the internal linker script is exactly the same as the C
> > version. That doesn't seem right to me.  I would expect them to be
> > at least a little different.
> >
> > Mike
> 
> Using a D-specific linker script in is outside the scope of GDC
> itself.  I'd have to make a patch to Binutils.
> 
> And yes, a bespoke linker script would solve many problems that are
> currently managed by the compiler.
> 
> Regards
> Iain

Please don't start working on a D specific linker script, cause I'm
already working on that ;-) I've only done moduleinfo so far, but TLS
is next, then shared library support.