[Bug lto/83816] [6/7 Regression] lto1: internal compiler error: compressed stream: data error

[olegendo at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83816

--- Comment #17 from Oleg Endo <olegendo at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #15)
> 
> I can reproduce it:
> 

Nice.

(In reply to Richard Biener from comment #16)
> Note your testcase only reproduces on the GCC 6 branch.  It is expected that
> the issue happens because of some exact length of the uncompressed or
> compressed section or maybe even the actual contents...

This particular case, yes.  However, I ran into this originally with GCC 7. 
During app development GCC 7 started to bail out while GCC 6 was working OK. 
So I switched back to GCC 6 and after some more app development, that one
started bailing out and GCC 7 does not on that case.

So I'd assume the issue is present in all versions.


> 
> Do you run into this very often?
> 

No, I can't say often.  But it surely is very annoying.  And when it happens
the only practical fix is to turn off LTO, which has a significant negative
impact on the code size.


> It may be possible to extract a "zlib testcase" ... maybe it is a genuine
> bug in it?  (however unlikely that is...)

Somehow I doubt that.
I'm now adding some logging around the code in lto-compress.c but so far I'm
not getting any useful info out of it.  The decompression fails right at the
first block in the stream.