https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88431
--- Comment #2 from Iain Buclaw <ibuclaw at gdcproject dot org> ---
(In reply to David Binderman from comment #1)
> This config line works fine:
>
> ../trunk/configure --prefix=/home/dcb/gcc/results.266950 \
> --disable-multilib \
> --disable-werror \
> --enable-checking=df,extra,fold,rtl,yes \
> --enable-languages=d
>
> so it looks like using -O3 in the top level Makefile causes trouble.
I see the following in the config.cache for libphobos:
lt_cv_prog_compiler_pic_works=${lt_cv_prog_compiler_pic_works=yes}
lt_cv_prog_compiler_pic_works_D=${lt_cv_prog_compiler_pic_works_D=no}
config.log:
configure:12414: checking if ./gcc/gdc -B./gcc/ PIC flag -fPIC works
configure:12432: ./gcc/gdc -B./gcc/ -c -nophoboslib -fno-moduleinfo -nostdinc
-g -O3 -march=native -Wlogical-op -fPIC conftest.d >&5
d21: warning: command line option '-Wlogical-op' is valid for C/C++/ObjC/ObjC++
but not for D
configure:12436: $? = 0
configure:12449: result: no
It looks like -Wlogical-op is the culprit, not -O3.
This is the condition in configure:
---
if (exit $ac_status) && test -s "$ac_outfile"; then
# The compiler can only warn and ignore the option if not recognized
# So say no if there are warnings other than the usual output.
$ECHO "$_lt_compiler_boilerplate" | $SED '/^$/d' >conftest.exp
$SED '/^$/d; /^ *+/d' conftest.err >conftest.er2
if test ! -s conftest.er2 || diff conftest.exp conftest.er2 >/dev/null; then
lt_cv_prog_compiler_pic_works_D=yes
fi
fi
