https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69757
--- Comment #5 from Edd Barrett <edd at theunixzoo dot co.uk> ---
I notice that the previous test *did* append -fPIC (and -DPIC). The failing
test does not show its input or compiler invocation, which makes this hard to
debug.
If you look in the libstdc++ configure script, you can see what happens:
---8<---
ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext
$LIBS >&5'
...
cat confdefs.h - <<_ACEOF >conftest.$ac_ext
/* end confdefs.h. */
int
main ()
{
;
return 0;
}
_ACEOF
# FIXME: Cleanup?
if { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_link\""; } >&5
(eval $ac_link) 2>&5
ac_status=$?
$as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
test $ac_status = 0; }; then :
gcc_no_link=no
else
gcc_no_link=yes
fi
if test x$gcc_no_link = xyes; then
# Setting cross_compile will disable run tests; it will
# also disable AC_CHECK_FILE but that's generally
# correct if we can't link.
cross_compiling=yes
EXEEXT=
---8<---
-fPIC is not in CFLAGS, so the test fails with an error like:
/usr/bin/ld: /tmp//ccdT7fwj.o: relocation R_X86_64_32 against `a local symbol'
can not be used when making a shared object; recompile with -fPIC
/tmp//ccdT7fwj.o: could not read symbols: Bad value
collect2: error: ld returned 1 exit status
Thus it tricks itself into thinking it is cross compiling.
I think the "no_executables" macros need to emit better debugging information
into config.log. (I would be happy to raise a separate bug for this if you
like).
