bootstrap comparison failure with bootstrap-lto

[Matt]

On Thu, 17 Nov 2011, Ian Lance Taylor wrote:

> Matt <matt@use.net> writes:
>
>> It *kind of* says why. I've pasted the output below. Unfortunately,
>> when the full build is finished, the prev-gcc/xgcc no longer
>> exists. When I test the conftest.c (copied and pasted from the log),
>> the stage1-gcc/xgcc and stage2-gcc/xgcc have no problem with it (of
>> course).
>
> OK, if this works after the build is complete, then you are going to
> need to stop the build in the middle.  Fortunately, this can be done
> easily enough by running "make configure-stage2-gcc".  That should stop
> after the stage2-gcc directory is configured.  At that point, you should
> see a stage2-gcc directory and a prev-gcc directory.  Presumably the
> stage2-gcc/config.log file will show a failure, and with luck you will
> be able to recreate that failure at that point.

Do I need to run a complete build first? When I run that make target right 
after configure, it fails in multiple ways when building from r181491:

matt@matt-desktop:~/src/gcc-trunk/obj$ ../configure --enable-bootstrap 
--prefix=/home/matt --enable-clocale=gnu --with-system-zlib 
--enable-shared --with-demangler-in-ld --enable-lto 
--with-build-config=bootstrap-lto --with-fpmath=sse 
--enable-languages=c,c++,lto

[...]

matt@matt-desktop:~/src/gcc-trunk/obj$ make configure-stage2-gcc
make[1]: Entering directory `/home/matt/src/gcc-trunk/obj'
mv: cannot stat `stage1-gcc': No such file or directory
make[1]: *** [stage2-start] Error 1
make[1]: Leaving directory `/home/matt/src/gcc-trunk/obj'
make: *** [configure-stage2-lto-plugin] Error 2

matt@matt-desktop:~/src/gcc-trunk/obj$ make configure-stage2-gcc
mkdir -p -- ./lto-plugin
Configuring stage 2 in ./lto-plugin
configure: creating cache ./config.cache
checking build system type... x86_64-unknown-linux-gnu
checking host system type... x86_64-unknown-linux-gnu
checking target system type... x86_64-unknown-linux-gnu
checking for a BSD-compatible install... /usr/bin/install -c
checking whether build environment is sane... yes
checking for a thread-safe mkdir -p... /bin/mkdir -p
checking for gawk... gawk
checking whether make sets $(MAKE)... yes
checking whether to enable maintainer-specific portions of Makefiles... no
checking for x86_64-unknown-linux-gnu-gcc... 
/home/matt/src/gcc-trunk/obj/./prev-gcc/xgcc 
-B/home/matt/src/gcc-trunk/obj/./prev-gcc/ 
-B/home/matt/x86_64-unknown-linux-gnu/bin/ 
-B/home/matt/x86_64-unknown-linux-gnu/bin/ 
-B/home/matt/x86_64-unknown-linux-gnu/lib/ -isystem 
/home/matt/x86_64-unknown-linux-gnu/include -isystem 
/home/matt/x86_64-unknown-linux-gnu/sys-include
checking for C compiler default output file name...
configure: error: in `/home/matt/src/gcc-trunk/obj/lto-plugin':
configure: error: C compiler cannot create executables
See `config.log' for more details.
make: *** [configure-stage2-lto-plugin] Error 77

Weird.

By the way, thanks for taking the time to help me work through debugging 
this issue so I can file a meaningful bug. I really appreciate it :)

--
tangled strands of DNA explain the way that I behave.
http://www.clock.org/~matt