> If --enable-multilib or --disable-multilib are passed then things
> are performed as today, more or less. If these flags are not
> explicitly given then gcc has to do something different
This sounds reasonable. We could have a specific check, with the following
cumulative conditions (to make it as unobtrusive as possible for current
users). If:
1. we build a native compiler
2. on x86_64-linux (and possible other x86_64 targets whose maintainers want
to opt in)
3. and neither --enable-multilib nor --disable-multilib were passed
then:
a. we check that the native compiler can handle 32-bit, by compiling a test
executable with the "-m32" option
b. if we fail, we error out of the configure process, indicating that this
can be overriden with --{enable,disable}-multilib
I suspect this might catch (at configure time) the large majority of users who
currently get stuck at stage 2 with the "gnu/stubs-32.h" error, while being
invisible to a large majority of the power users.
Question: what are the pitfalls of the test proposed above? are there typical
use cases that I have not thought of, and that would trigger this check?
FX
PS: I attach a tentative patch implementing such as check in configure.ac.
Index: configure.ac
===================================================================
--- configure.ac (revision 201292)
+++ configure.ac (working copy)
@@ -2861,6 +2861,26 @@ case "${target}" in
;;
esac
+# Special user-friendly check for native x86_64-linux build, if
+# multilib is not explicitly enabled.
+case "$target:$have_compiler:$host:$target:$enable_multilib" in
+ x86_64-*linux*:yes:$build:$build:)
+ # Make sure we have a developement environment that handles 32-bit
+ dev64=no
+ echo "int main () { return 0; }" > conftest.c
+ ${CC} -m32 -o conftest ${CFLAGS} ${CPPFLAGS} ${LDFLAGS} conftest.c
+ if test $? = 0 ; then
+ if test -s conftest || test -s conftest.exe ; then
+ dev64=yes
+ fi
+ fi
+ rm -f conftest*
+ if test x${dev64} != xyes ; then
+ AC_MSG_ERROR([I suspect your system does not have 32-bit developement
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.])
+ fi
+ ;;
+esac
+
# Default to --enable-multilib.
if test x${enable_multilib} = x ; then
target_configargs="--enable-multilib ${target_configargs}"
