[Bug debug/46749] gcc.dg/debug/pr41893-1.c -gdwarf-2 testsuite failures on darwin

[iains at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46749

--- Comment #20 from Iain Sandoe <iains at gcc dot gnu.org> 2010-12-02 09:09:49 UTC ---
(In reply to comment #19)
> On Wed, 1 Dec 2010, iains at gcc dot gnu.org wrote:

> > yeah - it's on my TODO (pr43751).
> > FWIW, some time ago, I did enquire about the difficulty of adding an
> > intentional additional post-link phase, with the feedback that it was prob. not
> > easy.
> 
> I thought about adding it to the collect-ld script instead.
> 
> Why do we want it only if there is a .c source available?  That doesn't
> make sense to me ... but i have no idea what dsymutil is supoosed to do,
> so ...

_any_ source, in fact -- hence PR43751 (because we don't even try to notice
Fortran at present).

----

OK. Without wishing to start any debate on whether the approach is "good" or
"bad".

The idea is that one saves time in the compile/debug loop by _not_ linking the
debug  - and leaving it in the object files.

This is fine until the c/l is of the form  " gcc some-source.ext    -o exe "
because then the object is temporary and deleted, thus not available for
debugging.

So, dsymtuil (which is a stand-alone debug-linker - used, in general, for the
packaging phase of a project) is invoked for such command lines.  It grabs the
debug from the files that will be deleted during the build.

this is quite helpful:
http://wiki.dwarfstd.org/index.php?title=Apple's_%22Lazy%22_DWARF_Scheme