[yocto] Unable to cross compile libgfortran for arm64

[Sergio Paracuellos]

Hi all,

I am trying to compile a complete system with fortran support using
yocto and I am having problems cross compiling libgfortran. The target
architecture is arm64 because the system will run in a xilinx mpsoc
based board. I need fortran support to compile lapack, openblas, scipy
and other python stuff that seems to need them. The yocto branch I am
using is the stable 'sumo'. So I do the following for enable fortran
support:

1) Add to my local.conf the following line:
FORTRAN_forcevariable = ",fortran"
2) Add a bbappend file for recipes-devtools/gcc/gcc-runtime_7.3.bb with:
RUNTIMETARGET += "libgfortran"

With the branch as it is when gcc-runtime is being build I end up with
an error because libbacktrace headers can't be found so I have to
apply the following PATCH to solve this first issue:

diff -Naur gcc-7.3.0/libgfortran/Makefile.in
gcc-7.3.0.modif/libgfortran/Makefile.in
--- gcc-7.3.0/libgfortran/Makefile.in 2018-01-25 09:17:54.059232055 +0100
+++ gcc-7.3.0.modif/libgfortran/Makefile.in 2019-01-08 12:42:00.583138367 +0100
@@ -582,7 +582,7 @@
 toolexeclib_DATA = libgfortran.spec
 libgfortran_la_LINK = $(LINK) $(libgfortran_la_LDFLAGS)
 libgfortran_la_LDFLAGS = -version-info `grep -v '^\#'
$(srcdir)/libtool-version` \
- $(LTLDFLAGS) $(LIBQUADLIB) ../libbacktrace/libbacktrace.la \
+ $(LTLDFLAGS) $(LIBQUADLIB) ../../libbacktrace/libbacktrace.la \
  $(HWCAP_LDFLAGS) \
  -lm $(extra_ldflags_libgfortran) \
  $(version_arg) -Wc,-shared-libgcc
@@ -603,7 +603,7 @@
       -I$(MULTIBUILDTOP)../libgcc \
       -I$(srcdir)/$(MULTISRCTOP)../libbacktrace \
       -I$(MULTIBUILDTOP)../libbacktrace \
-      -I../libbacktrace
+      -I../../libbacktrace

But then I get the following error:

| /home/sergio/YOCTO/build/tmp/work/aarch64-poky-linux/gcc-runtime/7.3.0-r0/recipe-sysroot-native/usr/bin/aarch64-poky-linux/../../libexec/aarch64-poky-linux/gcc/aarch64-poky-linux/7.3.0/ld:
../../libbacktrace/.libs/libbacktrace.a(dwarf.o): Relocations in
generic ELF (EM: 62)
| /home/sergio/YOCTO/build/tmp/work/aarch64-poky-linux/gcc-runtime/7.3.0-r0/recipe-sysroot-native/usr/bin/aarch64-poky-linux/../../libexec/aarch64-poky-linux/gcc/aarch64-poky-linux/7.3.0/ld:
../../libbacktrace/.libs/libbacktrace.a(dwarf.o): Relocations in
generic ELF (EM: 62)
| /home/sergio/YOCTO/build/tmp/work/aarch64-poky-linux/gcc-runtime/7.3.0-r0/recipe-sysroot-native/usr/bin/aarch64-poky-linux/../../libexec/aarch64-poky-linux/gcc/aarch64-poky-linux/7.3.0/ld:
../../libbacktrace/.libs/libbacktrace.a(dwarf.o): Relocations in
generic ELF (EM: 62)
| ../../libbacktrace/.libs/libbacktrace.a(dwarf.o): error adding
symbols: File in wrong format
| collect2: error: ld returned 1 exit status
| Makefile:1364: recipe for target 'libgfortran.la' failed
| make[1]: *** [libgfortran.la] Error 1
| make[1]: Leaving directory
'/home/sergio/YOCTO/build/tmp/work/aarch64-poky-linux/gcc-runtime/7.3.0-r0/gcc-7.3.0/build.aarch64-poky-linux.aarch64-poky-linux/aarch64-poky-linux/libgfortran'
| Makefile:1242: recipe for target 'all' failed
| make: *** [all] Error 2
| ERROR: oe_runmake failed
| WARNING: exit code 1 from a shell command.
| ERROR: Function failed: do_compile (log file is located at
/home/sergio/YOCTO/build/tmp/work/aarch64-poky-linux/gcc-runtime/7.3.0-r0/temp/log.do_compile.24547)
ERROR: Task (/home/sergio/YOCTO/workspace/poky/meta/recipes-devtools/gcc/gcc-runtime_7.3.bb:do_compile)
failed with exit code '1'

So It seems that libbacktrace is always built for my host architecture
instead of for arm64 bits...
Is this a known problem? Am I doing something wrong?

Thanks in advance for your time.

Best regards,
    Sergio Paracuellos

PD: I updated this info also in a bug related here which seems to be
fixed https://bugzilla.yoctoproject.org/show_bug.cgi?id=12394