[Bug other/72815] libmpx on i386

["vicencb at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=72815

--- Comment #4 from vicencb at gmail dot com ---
I can confirm that with the provided list of steps it is still reproducible.
To obtain the buildroot version use this:
####
cd /tmp
git clone git://git.buildroot.net/buildroot
cd buildroot
git checkout eb1a30a3d92c8ddbcc295cb48226604d6d881e25
####

And then following the steps, this is the error message reported (including the
command line invocation):
####
Making all in mpxrt
/bin/sh ../libtool  --tag=CC   --mode=compile
/tmp/buildroot/output/build/host-gcc-final-6.1.0/build/./gcc/xgcc
-B/tmp/buildroot/output/build/host-gcc-final-6.1.0/build/./gcc/
-B/tmp/i686-buildroot-linux-musl/usr/usr/i686-buildroot-linux-musl/bin/
-B/tmp/i686-buildroot-linux-musl/usr/usr/i686-buildroot-linux-musl/lib/
-isystem
/tmp/i686-buildroot-linux-musl/usr/usr/i686-buildroot-linux-musl/include
-isystem
/tmp/i686-buildroot-linux-musl/usr/usr/i686-buildroot-linux-musl/sys-include   
-DHAVE_CONFIG_H -I. -I../../../../libmpx/mpxrt -I..  -I../../../../libmpx/.. 
-fPIC -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64  -Os  -c
-o libmpx_la-mpxrt.lo `test -f 'mpxrt.c' || echo
'../../../../libmpx/mpxrt/'`mpxrt.c
libtool: compile: 
/tmp/buildroot/output/build/host-gcc-final-6.1.0/build/./gcc/xgcc
-B/tmp/buildroot/output/build/host-gcc-final-6.1.0/build/./gcc/
-B/tmp/i686-buildroot-linux-musl/usr/usr/i686-buildroot-linux-musl/bin/
-B/tmp/i686-buildroot-linux-musl/usr/usr/i686-buildroot-linux-musl/lib/
-isystem
/tmp/i686-buildroot-linux-musl/usr/usr/i686-buildroot-linux-musl/include
-isystem
/tmp/i686-buildroot-linux-musl/usr/usr/i686-buildroot-linux-musl/sys-include
-DHAVE_CONFIG_H -I. -I../../../../libmpx/mpxrt -I.. -I../../../../libmpx/..
-fPIC -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -Os -c
../../../../libmpx/mpxrt/mpxrt.c  -fPIC -DPIC -o .libs/libmpx_la-mpxrt.o
In file included from ../../../../libmpx/mpxrt/mpxrt.c:54:0:
../../../../libmpx/mpxrt/mpxrt.c: In function 'read_mpx_status_sig':
../../../../libmpx/mpxrt/mpxrt.h:52:42: error: invalid application of 'sizeof'
to incomplete type 'struct _libc_fpstate'
 #define XSAVE_OFFSET_IN_FPMEM    sizeof (struct _libc_fpstate)
                                          ^
../../../../libmpx/mpxrt/mpxrt.c:132:58: note: in expansion of macro
'XSAVE_OFFSET_IN_FPMEM'
   uint8_t *regs = (uint8_t *)uctxt->uc_mcontext.fpregs +
XSAVE_OFFSET_IN_FPMEM;
                                                          ^~~~~~~~~~~~~~~~~~~~~
####

And the gcc configuration from
/tmp/buildroot/output/build/host-gcc-final-6.1.0/build/gcc/config.log:
####
  $ /tmp/buildroot/output/build/host-gcc-final-6.1.0/gcc/configure
--srcdir=../../gcc --cache-file=./config.cache
--prefix=/tmp/i686-buildroot-linux-musl/usr/usr
--sysconfdir=/tmp/i686-buildroot-linux-musl/usr/etc --enable-static
--with-sysroot=/tmp/i686-buildroot-linux-musl/usr/usr/i686-buildroot-linux-musl/sysroot
--disable-__cxa_atexit --with-gnu-ld --disable-libssp --disable-multilib
--with-gmp=/tmp/i686-buildroot-linux-musl/usr/usr
--with-mpfr=/tmp/i686-buildroot-linux-musl/usr/usr --with-pkgversion=Buildroot
2016.08-git-01592-geb1a30a3d --with-bugurl=http://bugs.buildroot.net/
--enable-libquadmath --disable-libsanitizer --disable-tls --enable-plugins
--enable-lto --disable-libmudflap --enable-threads
--with-mpc=/tmp/i686-buildroot-linux-musl/usr/usr
--with-isl=/tmp/i686-buildroot-linux-musl/usr/usr --disable-decimal-float
--with-arch=i686
--with-build-time-tools=/tmp/i686-buildroot-linux-musl/usr/usr/i686-buildroot-linux-musl/bin
--enable-shared --disable-libgomp --enable-languages=c,c++,lto
--program-transform-name=s&^&i686-buildroot-linux-musl-&
--disable-option-checking --build=x86_64-pc-linux-gnu
--host=x86_64-pc-linux-gnu --target=i686-buildroot-linux-musl
####

Please, note that this is a crosscompiler.
I hope this helps fixing the bug.
Regards.