Newb build fails: -Werrors then Bootstrap comparison failure!

[will wray]

Thanks - "make clean" was the issue.
Nuking the directory and starting again from the configure command worked.

(My directory structure was confusing but followed the guidelines in the
docs).

On Wed, Sep 5, 2018 at 5:47 PM Jonathan Wakely <jwakely.gcc@gmail.com>
wrote:

> On Wed, 5 Sep 2018 at 21:14, will wray <wjwray@gmail.com> wrote:
> >
> > Following instructions here: https://gcc.gnu.org/install/index.html
> > on Fedora 28 with gcc (GCC) 8.1.1 20180712 (Red Hat 8.1.1-5).
> >
> > First, the build hit a couple of -Werror fails so I reconfigured with
> > -disable-werror
> > then I get: Comparing stages 2 and 3, Bootstrap comparison failure!
> >
> > Do I disable comparison? Disable bootstrap?
> > Any other suggestions on doing a fresh build?
> >
> > > svn checkout svn://gcc.gnu.org/svn/gcc/trunk gcc
> > > mkdir build
> > > cd build
> > > mkdir gcc
> > > mkdir install
> > > cd gcc
> > > ../../gcc/configure --prefix=$HOME/repos/build/install
> > --enable-languages=c,c++ --disable-multilib
> > > make BOOT_CFLAGS='-O' bootstrap
> >
> > ...
> > ./insn-opinit.h:358:40: error: ‘icode’ may be used uninitialized in this
> > function [-Werror=maybe-uninitialized]
> > 358 | #define GEN_FCN(CODE) (insn_data[CODE].genfun)
> > ...
> > ../../../gcc/gcc/config/i386/i386.c:4514:32: error: ‘mask’ may be used
> > uninitialized in this function [-Werror=maybe-uninitialized]
> > 4514 |    opts->x_recip_mask_explicit |= mask;
> >      |    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~
> > cc1plus: all warnings being treated as errors
> > ...
> >
> > > make clean
>
> "make clean" is known to not do a very good job of cleaning up. Just
> delete the entire ~/repos/build/gcc directory and start again from the
> configure command.
>
>
> > > ../../gcc/configure --prefix=$HOME/repos/build/install
>
> The installation docs say "building where objdir is a subdirectory of
> srcdir is unsupported."
>
> It can work, but I avoid it. Build in a directory outside the source dir.
>
>
> > --enable-languages=c,c++ --disable-multilib -disable-werror
> > > make
> >
> > ...
> > Comparing stages 2 and 3
> > Bootstrap comparison failure!
> > gcc/gcc.o differs
> > gcc/plugin.o differs
> > ...
>
> I don't know why you'd get a comparison failure. If it still happens
> after starting again in an empty directory try it without the
> BOOT_CFLAGS=-O
>