Error building bootstrapped multilib GCC

[Ben Sferrazza <bsferrazza at avnera dot com>]

Hi,

I'm trying to build a multlib (m64,mx32,m32) bootstrapped toolchain
following much of the guidance of Linux From Scratch, but am encoutering
errors on the 2nd pass build of GCC 7.3.0. *The actual error is found near
the end of this email, if you'd like to skip over the background*. I've
previously built a 64-bit bootstrapped toolchain on this same system
without issue following LFS. Unfortunately I need 32-bit support for some
legacy CAD software I'm using at work.

Here's the multilib LFS guide I am following. I've made a few adjustments
since this is a couple years old to work with the latest versions of
binutils, glibc, and gcc.
https://www.williamfeely.info/lfs-multilib/

Here's my configure setup, where $LFS_TGT is x86_64-lfs-linux-gnu, the
cross-compiled GCC that I built in pass 1. $LFS_COMMON is just the
temporary path I'm using as I build up the toolchain. The linux{64}.h files
under gcc/config were patched to correctly set the linker paths to that
temporary toolchain directory, just as is described in all LFS books. I
also edited gcc/config/i386/t-linux64 to set "MULTILIB_OSDIRNAMES =
m64=../lib m32=../lib32 mx32=../libx32", as is also described in the
multilib LFS book.

CC="$LFS_TGT-gcc -B$LFS_COMMON/lib/"                  \
CXX="$LFS_TGT-g++ -B$LFS_COMMON/lib/"                 \
AR=$LFS_TGT-ar                                        \
RANLIB=$LFS_TGT-ranlib                                \
../configure                                          \
  --prefix=$LFS_COMMON                                \
  --with-local-prefix=$LFS_COMMON                     \
  --with-native-system-header-dir=$LFS_COMMON/include \
  --enable-languages=c,c++                            \
  --disable-libstdcxx-pch                             \
  --enable-multilib                                   \
  --with-multilib-list=m32,m64,mx32                   \
  --disable-bootstrap                                 \
  --disable-libgomp

At first I ran it without --enable-multilib, but it complains during
configure without it as follows.

/nfs/home/bsferrazza/clfs/local/bin/../lib/gcc/x86_64-lfs-linux-gnu/7.3.0/../../../../x86_64-lfs-linux-gnu/bin/ld:
i386:x86-64 architecture of input file `/home/tools/local/lib/crtn.o' is
incompatible with i386 output
/nfs/home/bsferrazza/clfs/local/bin/../lib/gcc/x86_64-lfs-linux-gnu/7.3.0/../../../../x86_64-lfs-linux-gnu/bin/ld:
/home/tools/local/lib/crt1.o: file class ELFCLASS64 incompatible with
ELFCLASS32
/nfs/home/bsferrazza/clfs/local/bin/../lib/gcc/x86_64-lfs-linux-gnu/7.3.0/../../../../x86_64-lfs-linux-gnu/bin/ld:
final link failed: File in wrong format
collect2: error: ld returned 1 exit status
configure: error: I suspect your system does not have 32-bit development
libraries (libc and headers). If you have them, rerun configure with
--enable-multilib. If you do not have them, and want to build a 64-bit-only
compiler, rerun configure with --disable-multilib.

It's worth noting that pass 1 did not have --enable-multilib set and it
configured just fine even with setting --with-multilib-list and making the
MULTILIB_OSDIRNAMES edit. However, that first pass is cross-compiled by
setting --target=$LFS_TGT, so presumably that's why it doesn't have any
issues.

Now for the actual error during compilation of the native GCC build with
multilib support. It gets to building the 32-bit version of zlib, and tries
to run make in 32/zlib, but there is no Makefile there.

make[4]: Entering directory
'/nfs/home/bsferrazza/clfs/sources/gcc-7.3.0/gcc-build/32/zlib'
make[4]: *** No rule to make target 'all'.  Stop.
make[4]: Leaving directory
'/nfs/home/bsferrazza/clfs/sources/gcc-7.3.0/gcc-build/32/zlib'
make[3]: *** [Makefile:736: multi-do] Error 1
make[3]: Leaving directory
'/nfs/home/bsferrazza/clfs/sources/gcc-7.3.0/gcc-build/zlib'
make[2]: *** [Makefile:533: all-multi] Error 2
make[2]: Leaving directory
'/nfs/home/bsferrazza/clfs/sources/gcc-7.3.0/gcc-build/zlib'
make[1]: *** [Makefile:9776: all-zlib] Error 2
make[1]: Leaving directory
'/nfs/home/bsferrazza/clfs/sources/gcc-7.3.0/gcc-build'
make: *** [Makefile:903: all] Error 2

One thing worth mentioning is that I have always required using
-B/toolchain/path/lib/ when using the cross-compiled gcc for the first
steps of LFS, despite it showing no need for -B in the LFS books of recent
years. Otherwise it won't find the correct crt*.o files for instance. This
worked fine for me when doing a single lib 64-bit toolchain, but I'm not
sure if this is causing issues for a multilib build. If I'm compiling a
dummy.c file using that cross-compiled multilib version of gcc that was
built in pass 1, I must use the appropiate -B path when compiling it for
32-bits. i.e. "$LFS_TGT-gcc -m32 -B/toolchain/path/lib32/ dummy.c". But
when building the 2nd pass of gcc, I can obviously only pass it a single CC
environment variable, and choose "CC=$LFS_TGT-gcc -B/toolchain/path/lib/",
as shown in the configure setup above (which is what I'd use for compiling
64-bit binaries). So it's unclear if this could be contributing to the
error I'm seeing, and what potential workarounds I can take.