[Bug lto/81968] [8 regression] early lto debug objects make Solaris ld SEGV

["ro at CeBiTec dot Uni-Bielefeld.DE" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81968

--- Comment #55 from ro at CeBiTec dot Uni-Bielefeld.DE <ro at CeBiTec dot Uni-Bielefeld.DE> ---
> --- Comment #54 from Richard Biener <rguenth at gcc dot gnu.org> ---
> Created attachment 43075
>   --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=43075&action=edit
> Updated patch with SHT_GROUP and extended section index handling
>
> More fixes accumulated.  Works for the large # input section testcase now. 
> Also goes happily into stage2 with bootstrap-lto.

Solaris ld is almost happy again with this patch :-)

There's one last failure remaining:

FAIL: gcc.dg/debug/pr41893-1.c -gdwarf-2 -g3 (test for excess errors)
Excess errors:
ld: fatal: relocation error: R_386_32: file /var/tmp//cctCq6ccdebugobjtem:
section [11].rel.debug_macro: symbol
.debug_macro%wm4.0.3a71fa84800da6806674b2243f0bb574 (section): symbol has been
discarded with discarded section:
[6].debug_macro%wm4.0.3a71fa84800da6806674b2243f0bb574

Compiling the test with -save-temps works, however...

Here's what I find: the error happens during the ld -r stage again.  The
invocations boil down to

$ lto-wrapper pr41893-1.o pr41893-2.o
$ ld -r -o ccO7nK8bdebugobj cc0vpSPddebugobjtem ccTcSAFadebugobjtem

elfdump complains about those objects:

cc0vpSPddebugobjtem: [2: .group%wm4.0.3a71fa84800da6806674b2243f0bb574][2]:
invalid section index: 0

as can be seen with elfdump -g:

Group Section:  .group%wm4.0.3a71fa84800da6806674b2243f0bb574
  Signature Symbol: wm4.0.3a71fa84800da6806674b2243f0bb574
  Members:
    index   flags / section
      [0]   [ COMDAT ]
      [1]   .debug_macro%wm4.0.3a71fa84800da6806674b2243f0bb574
      [2]   <invalid section>

while readelf -g doesn't seem to care about the section index here:

COMDAT group section [    2] `.group%wm4.0.3a71fa84800da6806674b2243f0bb574'
[wm4.0.3a71fa84800da6806674b2243f0bb574] contains 2 sections:
   [Index]    Name
   [    6]   .debug_macro%wm4.0.3a71fa84800da6806674b2243f0bb574
   [    0]   

The input object had

 COMDAT group section [    2] `.group%wm4.0.3a71fa84800da6806674b2243f0bb574'
[wm4.0.3a71fa84800da6806674b2243f0bb574] contains 2 sections:
   [Index]    Name
   [    7]   .gnu.debuglto_.debug_macro%wm4.0.3a71fa84800da6806674b2243f0bb574
   [   25]   .debug_macro%wm4.0.3a71fa84800da6806674b2243f0bb574

        Rainer