Re: bootstrap comparison failure with bootstrap-lto

[Ian Lance Taylor <iant at google dot com>]

Matt <matt@use.net> writes:

> On Mon, 14 Nov 2011, Ian Lance Taylor wrote:
>
>> Matt <matt@use.net> writes:
>>
>>> I am getting this on Ubuntu 11.10/amd64. If I remove the
>>> --with-build-config=bootstrap-lto, the build succeeds just fine. Is
>>> this a known problem, or should I file a bug? (A search of bugzilla
>>> didn't bring up this specific symptom.)
>>
>>> libcpp/lex.o differs
>>
>> What are the differences between stage2-libcpp/lex.o and
>> stage3-libcpp/lex.o?  Ignore the fact that one will have debug info and
>> the other will not.  Look at the readelf -S output for both files, and
>> see if there are any differences in sections whose names do not start
>> with ".debug".
>
> in stage2-libcpp/lex.o:
>   [79] .init_array       INIT_ARRAY       0000000000000000  00021280
>        0000000000000008  0000000000000000  WA       0     0     8
>   [80] .rela.init_array  RELA             0000000000000000  0003a8e8
>        0000000000000018  0000000000000018          101    79     8
>
>
>
> in stage3-libcpp/lex.o:
>   [79] .ctors            PROGBITS         0000000000000000  00021280
>        0000000000000008  0000000000000000  WA       0     0     8
>   [80] .rela.ctors       RELA             0000000000000000  0003a8e0
>        0000000000000018  0000000000000018          101    79     8
>
>
> There's a few other minor differences, but they're related to debug
> stuff, as far as I can tell.
>
>
>> Also, what linker are you using?
>
> ld --version outputs:
> GNU ld (GNU Binutils for Ubuntu) 2.21.53.20110810
>
> AFAIK, I'm using the default linker for Ubuntu 11.10/amd64.


Thanks.  It appears that for some reason your stage2 build is using
--enable-initfini-array while your stage3 build is using
--disable-initfini-array.  The default value for this configure option
is set by the configure script.

grep for gcc_cv_initfini_array in stage1-gcc/config.log and
stage2-gcc/config.log.  I am guessing that they will have different
values.

Look in stage1-gcc/config.log and stage2-gcc/config.log.  Look for
"checking for .preinit_array/.init_array/.fini_array support".  It
should be followed by a compile and run of conftest.  I'm guessing that
one of those runs succeeded and one failed.  See if config.log says why.

Ian