Strange strip/bfd behavior on x86_64 when --emit-relocs was used.

[Ignacy Gawedzki <i at lri dot fr>]

Hi,

I have a strange issue with strip on x86_64.

It happens in the following quite simple case:

  echo 'void f(void) {}' > foo.c
  cc -c foo.c
  cc -shared -nostartfiles -o foo.so -Wl,--emit-relocs foo.o

Now foo.so has a .rela.eh_frame section, as per readelf -S.  If I understand
correctly, libbfd's bfd_map_over_sections doesn't call the callback on .rel*
sections, since it's doing something clever with it.  Nevertheless, if I strip
foo.so once, the .rela.eh_frame section is still there according to readelf
-S.  Now libbfd's bfd_map_over_sections strangely calls the callback on it.
If I strip foo.so again, then .rela.eh_frame is still there, but strangely at
the same offset as the .comment section.  If I try to strip foo.so once more,
I get the following errors:

  BFD: st3ppeRZ: section `.dynamic' can't be allocated in segment 1
  LOAD: .dynamic
  BFD: st3ppeRZ: The first section in the PT_DYNAMIC segment is not the .dynamic
  section
  strip:st3ppeRZ[.note.gnu.build-id]: Bad value
  BFD: st3ppeRZ: section `.dynamic' can't be allocated in segment 1
  LOAD: .dynamic
  BFD: st3ppeRZ: The first section in the PT_DYNAMIC segment is not the .dynamic
  section
  strip:st3ppeRZ: Bad value

So there's obviously something wrong.  I suppose strip should be idempotent.

This happens with:

  GNU strip (GNU Binutils for Ubuntu) 2.20.51-system.20100908

Whereas with

  GNU strip (GNU Binutils for Debian) 2.21.0.20110302

I have a slightly different behavior.  After the third strip, I get

  BFD: st8Of0vN: section `.dynamic' can't be allocated in segment 1
  LOAD: .dynamic

but a binary output is produced.  After a fourth strip, I get

  BFD: stk8iNOY: warning: allocated section `.dynamic' not in segment

I tried to ask strip to explicitly remove that .rela.eh_frame section from the
freshly produced foo.so, but it skips it (as per ltrace).  It works only when
I ask strip a second time. :/

Is it a known issue or maybe am I doing something wrong?

Thanks for your help.

Ignacy

-- 
 "The whole problem with the world is that fools and fanatics are
   always so certain of themselves, and wiser people so full of doubts."
                                                 - Bertrand Russell