[ARM/FDPIC v5 02/21] [ARM] FDPIC: Handle arm*-*-uclinuxfdpiceabi in configure scripts
Christophe Lyon
christophe.lyon@linaro.org
Fri Jul 12 13:25:00 GMT 2019
On Fri, 12 Jul 2019 at 08:49, Richard Sandiford
<richard.sandiford@arm.com> wrote:
>
> Christophe Lyon <christophe.lyon@st.com> writes:
> > The new arm-uclinuxfdpiceabi target behaves pretty much like
> > arm-linux-gnueabi. In order the enable the same set of features, we
> > have to update several configure scripts that generally match targets
> > like *-*-linux*: in most places, we add *-uclinux* where there is
> > already *-linux*, or uclinux* when there is already linux*.
> >
> > In gcc/config.gcc and libgcc/config.host we use *-*-uclinuxfdpiceabi
> > because there is already a different behaviour for *-*uclinux* target.
> >
> > In libtool.m4, we use uclinuxfdpiceabi in cases where ELF shared
> > libraries support is required, as uclinux does not guarantee that.
> >
> > 2019-XX-XX Christophe Lyon <christophe.lyon@st.com>
> >
> > config/
> > * futex.m4: Handle *-uclinux*.
> > * tls.m4 (GCC_CHECK_TLS): Likewise.
> >
> > gcc/
> > * config.gcc: Handle *-*-uclinuxfdpiceabi.
> >
> > libatomic/
> > * configure.tgt: Handle arm*-*-uclinux*.
> > * configure: Regenerate.
> >
> > libgcc/
> > * config.host: Handle *-*-uclinuxfdpiceabi.
> >
> > libitm/
> > * configure.tgt: Handle *-*-uclinux*.
> > * configure: Regenerate.
> >
> > libstdc++-v3/
> > * acinclude.m4: Handle uclinux*.
> > * configure: Regenerate.
> > * configure.host: Handle uclinux*
> >
> > * libtool.m4: Handle uclinux*.
>
> Has the libtool.m4 patch been submitted to upstream libtool?
> I think this is supposed to be handled by submitting there first
> and then cherry-picking into gcc, so that the change isn't lost
> by a future import.
Yes, this was raised by Joseph when I first posted this patch series last year:
https://gcc.gnu.org/ml/gcc-patches/2018-05/msg01507.html
I sent a patch there:
https://lists.gnu.org/archive/html/libtool-patches/2018-05/msg00000.html
but didn't get any feedback :-(
>
> > [...]
> >
> > diff --git a/config/tls.m4 b/config/tls.m4
> > index 1a5fc59..a487aa4 100644
> > --- a/config/tls.m4
> > +++ b/config/tls.m4
> > @@ -76,7 +76,7 @@ AC_DEFUN([GCC_CHECK_TLS], [
> > dnl Shared library options may depend on the host; this check
> > dnl is only known to be needed for GNU/Linux.
> > case $host in
> > - *-*-linux*)
> > + *-*-linux* | -*-uclinux*)
> > LDFLAGS="-shared -Wl,--no-undefined $LDFLAGS"
> > ;;
> > esac
>
> Is this right for all uclinux targets?
So...... Let me bring back a bit of history/context. When we developed
FDPIC support in ST several years ago, we used arm-linux-uclibceabi as
triplet.
But when I posted the binutils patch series, Joseph said it wasn't
appropriate and suggested arm-*-uclinuxfdpiceabi instead.
https://sourceware.org/ml/binutils/2018-03/msg00324.html
This had an impact on the GCC side, because some parts weren't enabled
anymore after the triplet change, so I had to introduce this
configure* patch to restore the missing features.
Then, I wondered about the impact on other uclinux targets, but it was
hard to find a supported-supposed-to-work one.
I asked for help on the gcc list
(https://gcc.gnu.org/ml/gcc/2018-10/msg00154.html), and finally
managed to build and test an xtensa toolchain.
And this has an impact on the results on xtensa, as I reported in V3
of this patch:
https://gcc.gnu.org/ml/gcc-patches/2018-11/msg00713.html
But given the little feedback, I'm wondering whether uclinux targets
are actually still alive/maintained?
>
> > diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4
> > index 84258d8..cb0fdc5 100644
> > --- a/libstdc++-v3/acinclude.m4
> > +++ b/libstdc++-v3/acinclude.m4
>
> It'd probably be worth splitting out the libstdc++-v3 bits and
> submitting them separately, cc:ing libstdc++@gcc.gnu.org. But...
>
> > @@ -1404,7 +1404,7 @@ AC_DEFUN([GLIBCXX_ENABLE_LIBSTDCXX_TIME], [
> > ac_has_nanosleep=yes
> > ac_has_sched_yield=yes
> > ;;
> > - gnu* | linux* | kfreebsd*-gnu | knetbsd*-gnu)
> > + gnu* | linux* | kfreebsd*-gnu | knetbsd*-gnu | uclinux*)
> > AC_MSG_CHECKING([for at least GNU libc 2.17])
> > AC_TRY_COMPILE(
> > [#include <features.h>],
>
> is this the right thing to do? It seems odd to be testing the glibc
> version for uclibc.
As said above, I needed to set ac_has_nanosleep and ac_has_sched_yield so that
tests continue to pass after the triplet change. Looks like I got the
effect I wanted, but
not in the right way indeed.
> Do you want to support multiple possible settings of
> ac_has_clock_monotonic and ac_has_clock_realtime? Or could you just
> hard-code the values, given particular baseline assumptions about the
> version of uclibc etc.? Hard-coding would then make....
Right, I think it could be hardcoded.
>
> > @@ -1526,7 +1526,7 @@ AC_DEFUN([GLIBCXX_ENABLE_LIBSTDCXX_TIME], [
> >
> > if test x"$ac_has_clock_monotonic" != x"yes"; then
> > case ${target_os} in
> > - linux*)
> > + linux* | uclinux*)
> > AC_MSG_CHECKING([for clock_gettime syscall])
> > AC_TRY_COMPILE(
> > [#include <unistd.h>
>
> ...this redundant.
Indeed.
>
> > @@ -2415,7 +2415,7 @@ AC_DEFUN([GLIBCXX_ENABLE_CLOCALE], [
> > # Default to "generic".
> > if test $enable_clocale_flag = auto; then
> > case ${target_os} in
> > - linux* | gnu* | kfreebsd*-gnu | knetbsd*-gnu)
> > + linux* | gnu* | kfreebsd*-gnu | knetbsd*-gnu | uclinux*)
> > enable_clocale_flag=gnu
> > ;;
> > darwin*)
>
> This too seems to be choosing a glibc setting for a uclibc target.
Indeed, but I'd have to re-run the tests without this hunk to remember
which ones fail with enable_clocale_flag=generic.
>
> > @@ -2661,7 +2661,7 @@ AC_DEFUN([GLIBCXX_ENABLE_ALLOCATOR], [
> > # Default to "new".
> > if test $enable_libstdcxx_allocator_flag = auto; then
> > case ${target_os} in
> > - linux* | gnu* | kfreebsd*-gnu | knetbsd*-gnu)
> > + linux* | gnu* | kfreebsd*-gnu | knetbsd*-gnu | uclinux*)
> > enable_libstdcxx_allocator_flag=new
> > ;;
> > *)
>
> The full case is:
>
> # Probe for host-specific support if no specific model is specified.
> # Default to "new".
> if test $enable_libstdcxx_allocator_flag = auto; then
> case ${target_os} in
> linux* | gnu* | kfreebsd*-gnu | knetbsd*-gnu)
> enable_libstdcxx_allocator_flag=new
> ;;
> *)
> enable_libstdcxx_allocator_flag=new
> ;;
> esac
> fi
>
> which looks a bit redundant :-)
Good catch
Thanks a lot for your feedback.
Christophe
>
> Thanks,
> Richard
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