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Additional RFC, Re: RFC automatic linkage of libquadmath with gfortran: PR driver/46516; libgfortran.spec, multilib search path
Hello all...
On 22 Nov 2010, at 07:28, Tobias Burnus wrote:
On 11/22/2010 12:07 AM, Michael Matz wrote:
I have another improvement here. I'm regularly testing uninstalled
compilers (or compilers installed in temp paths). This exposed a
problem
in that the .spec file is only found when the proper -L option is
given
(that's okay), which it usually isn't for non-linking commands. In
that
case lang_specific_pre_link is nevertheless called, tries to include
libgfortran.spec and fails. Hence, let's remember if we're in a
non-link
run, and not do anything with that .spec file.
Regstrapping on x86_64-linux in progress. Okay if that passes?
OK. Thanks for the patch!
I have some requested additions (for Darwin), but also some
observations/suggestions...
Firstly, when one hijacks *lib, it means that the target has no chance
to do spec substitutions/outfile removal
-- this is because the new libs are added after "output files" have
been evaluated in the LINK_COMMAND.
-- because libs are not treated as switches, one cannot switch on them
either
So that means that we must ensure:
(a) that we don't add any libs that the target doesn't want
(b) if there are any substitutions, unfortunately they need to appear
in the libgfortran spec - since we can't hide them away in the target
LINK_COMMAND
====
Firstly, I wonder if it would be better to hijack the
"*link_gcc_c_sequence" rather than "*lib"
(this means that the correct link sequence for libgcc/lc will follow
directly after the libgfortran/libquadmath sequence .
... which also means one doesn't have to embed any differences in the
way targets make that sequence)
like this:
===================================================================
--- libgfortran/libgfortran.spec.in (revision 167142)
+++ libgfortran/libgfortran.spec.in (working copy)
@@ -2,7 +2,10 @@
# This spec file is read by gfortran when linking.
# It is used to specify the libraries we need to link in, in the right
# order.
-#
-%rename lib liborig
-*lib: @LIBQUADSPEC@ -lm %(libgcc) %(liborig)
+# Hijack the link sequence for libgcc and lc so that we can interpose
+# the quad math and system math libs just before it. This also works
for
+# targets that only link lgcc once.
+
+%rename link_gcc_c_sequence link_gcc_c_sequence_orig
+*link_gcc_c_sequence: @LIBQUADSPEC@ @LIBMSPEC@ %
(link_gcc_c_sequence_orig)
If that's not OK - then we need to suppress the additional %(libgcc)
for darwin too.
NOTE; I think that if we do this we can lose all the libm agonizing
from gfortranspec.c - because the libgfortan.spec will automatically
place "-lm" just before the libgcc/lc sequence for targets that
require it.
(If the user inserts a '-lm' by hand we should just pass that through
- on the assumption that the user knows what (s)he is doing).
-----
Secondly to cater for Darwin (and any other target that doesn't want -
lm unconditionally);
(plus our spec substitution for the static case)
Index: libgfortran/configure.ac
===================================================================
--- libgfortran/configure.ac (revision 167142)
+++ libgfortran/configure.ac (working copy)
@@ -515,6 +515,17 @@ else
multilib_arg=
fi
+# Allow for targets which don't need/want -lm.
+case "${host}" in
+ *-darwin*)
+ LIBMSPEC=
+ ;;
+ *)
+ LIBMSPEC="-lm"
+ ;;
+esac
+AC_SUBST(LIBMSPEC)
+
# Write our Makefile and spec file.
AC_CONFIG_FILES([
Makefile
Index: libgfortran/acinclude.m4
===================================================================
--- libgfortran/acinclude.m4 (revision 167142)
+++ libgfortran/acinclude.m4 (working copy)
@@ -329,7 +329,10 @@ AC_DEFUN([LIBGFOR_CHECK_FLOAT128], [
if test "x$libgfor_cv_have_as_needed" = xyes; then
LIBQUADSPEC="%{static-libgfortran:--as-needed} -lquadmath %
{static-libgfortran:--no-as-needed}"
else
- LIBQUADSPEC="-lquadmath"
+ case "${target}" in
+ *86*-*-darwin*) LIBQUADSPEC="%{static|static-libgcc|static-
libgfortran: libquadmath.a%s; : -lquadmath}" ;;
+ *) LIBQUADSPEC="-lquadmath" ;;
+ esac
fi
if test -f ../libquadmath/libquadmath.la; then
LIBQUADLIB=../libquadmath/libquadmath.la
====
Thoughts? OK for trunk?
(tested on *-darwin9, and x86_64-unk-linux)
cheers,
Iain