[PATCH 1/1] support cross compilation

[Érico Nogueira]

Hi! Are you sure this is necessary? In Void Linux, we cross compile
elfutils for arm and aarch64 without any issue, and I have built it a
few times for powerpc as well.

On Wed May 26, 2021 at 4:32 AM -03, Petr Ovtchenkov wrote:
> Possible problem with out-of-tree build expected
> ---
> Makefile.am | 2 +-
> configure.ac | 6 ++++++
> lib-host/Makefile.am | 47 ++++++++++++++++++++++++++++++++++++++++++++
> libcpu/Makefile.am | 11 +++++++++++
> 4 files changed, 65 insertions(+), 1 deletion(-)
> create mode 100644 lib-host/Makefile.am
>
> diff --git a/Makefile.am b/Makefile.am
> index 9c47afa9..b93839ec 100644
> --- a/Makefile.am
> +++ b/Makefile.am
> @@ -26,7 +26,7 @@ AM_MAKEFLAGS = --no-print-directory
>  
> pkginclude_HEADERS = version.h
>  
> -SUBDIRS = config lib libelf libcpu backends libebl libdwelf libdwfl
> libdw \
> +SUBDIRS = config lib lib-host libelf libcpu backends libebl libdwelf
> libdwfl libdw \
> libasm debuginfod src po doc tests
>  
> EXTRA_DIST = elfutils.spec GPG-KEY NOTES CONTRIBUTING \
> diff --git a/configure.ac b/configure.ac
> index b348a717..432b961a 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -88,6 +88,7 @@ AS_IF([test "$use_locks" = yes],
> AH_TEMPLATE([USE_LOCKS], [Defined if libraries should be thread-safe.])
>  
> AC_PROG_CC
> +AX_PROG_CC_FOR_BUILD
> AC_PROG_RANLIB
> AC_PROG_YACC
> AM_PROG_LEX
> @@ -96,6 +97,8 @@ m4_ifdef([AM_PROG_AR], [AM_PROG_AR])
> AC_CHECK_TOOL([READELF], [readelf])
> AC_CHECK_TOOL([NM], [nm])
>  
> +AM_CONDITIONAL([CROSS], [test "x$cross_compiling" = xyes])
> +
> # We use -std=gnu99 but have explicit checks for some language
> constructs
> # and GNU extensions since some compilers claim GNU99 support, but don't
> # really support all language extensions. In particular we need
> @@ -593,6 +596,9 @@ AC_CONFIG_FILES([doc/Makefile])
> dnl Support library.
> AC_CONFIG_FILES([lib/Makefile])
>  
> +dnl Support library.
> +AC_CONFIG_FILES([lib-host/Makefile])
> +
> dnl ELF library.
> AC_CONFIG_FILES([libelf/Makefile])
>  
> diff --git a/lib-host/Makefile.am b/lib-host/Makefile.am
> new file mode 100644
> index 00000000..9316c8ed
> --- /dev/null
> +++ b/lib-host/Makefile.am
> @@ -0,0 +1,47 @@
> +## Process this file with automake to create Makefile.in
> +##
> +## Copyright (C) 1996-2011 Red Hat, Inc.
> +## This file is part of elfutils.
> +##
> +## This file is free software; you can redistribute it and/or modify
> +## it under the terms of either
> +##
> +## * the GNU Lesser General Public License as published by the Free
> +## Software Foundation; either version 3 of the License, or (at
> +## your option) any later version
> +##
> +## or
> +##
> +## * the GNU General Public License as published by the Free
> +## Software Foundation; either version 2 of the License, or (at
> +## your option) any later version
> +##
> +## or both in parallel, as here.
> +##
> +## elfutils is distributed in the hope that it will be useful, but
> +## WITHOUT ANY WARRANTY; without even the implied warranty of
> +## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> +## General Public License for more details.
> +##
> +## You should have received copies of the GNU General Public License
> and
> +## the GNU Lesser General Public License along with this program. If
> +## not, see <http://www.gnu.org/licenses/>.
> +##
> +if CROSS
> +
> +include $(top_srcdir)/config/eu.am
> +AM_CFLAGS += $(fpic_CFLAGS)
> +AM_CPPFLAGS += -D_GNU_SOURCE -I$(srcdir)/../lib -I$(srcdir)/../libelf
> +
> +noinst_LIBRARIES = libeu.a
> +
> +$(libeu_a_OBJECTS): CC=${CC_FOR_BUILD}
> +
> +libeu_a_SOURCES = ../lib/xstrdup.c ../lib/xstrndup.c ../lib/xmalloc.c
> ../lib/next_prime.c \
> + ../lib/crc32.c ../lib/crc32_file.c \
> + ../lib/color.c ../lib/printversion.c
> +
> +if !GPROF
> +xmalloc_CFLAGS = -ffunction-sections
> +endif
> +endif
> diff --git a/libcpu/Makefile.am b/libcpu/Makefile.am
> index 43844ecf..5086f8be 100644
> --- a/libcpu/Makefile.am
> +++ b/libcpu/Makefile.am
> @@ -27,6 +27,13 @@
> ## the GNU Lesser General Public License along with this program. If
> ## not, see <http://www.gnu.org/licenses/>.
> ##
> +
> +if CROSS
> +i386_gendis_LINK = ${CC_FOR_BUILD} ${LDFLAGS} -o $@
> +
> +$(i386_gendis_OBJECTS): CC=${CC_FOR_BUILD}
> +endif

Isn't this hardcoding an assumption that the build machine is x86?

> +
> include $(top_srcdir)/config/eu.am
> AM_CPPFLAGS += -I$(srcdir)/../libelf -I$(srcdir)/../libebl \
> -I$(srcdir)/../libdw -I$(srcdir)/../libasm
> @@ -79,7 +86,11 @@ endif
>  
> i386_lex_no_Werror = yes
>  
> +if CROSS
> +libeu = ../lib-host/libeu.a
> +else
> libeu = ../lib/libeu.a
> +endif
>  
> i386_lex_CFLAGS = -Wno-unused-label -Wno-unused-function
> -Wno-sign-compare \
> -Wno-implicit-fallthrough
> --
> 2.29.2.1.g08c1adf7b9