From c7c769990bca3049bc389dcbd9985adaec134946 Mon Sep 17 00:00:00 2001
From: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Date: Sat, 29 Aug 2015 11:59:18 +0200
Subject: [PATCH] Use the native compiler to build generate_cookbook

The generate_cookbook binary needs to be executed at build time. When
cross-compiling, this means that it should be built with the native
compiler rather than the cross-compiler.

To achieve this, this commit imports the AX_CC_FOR_BUILD autoconf
macro from the GNU Autoconf Archive project, and adjusts
src/Makefile.am to use CC_FOR_BUILD to build generate_cookbook.

Based on initial work by Bernd Kuhls.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
---
 Makefile.am           |  1 +
 configure.ac          |  2 ++
 m4/ax_cc_for_build.m4 | 77 +++++++++++++++++++++++++++++++++++++++++++++++++++
 src/Makefile.am       |  3 ++
 4 files changed, 83 insertions(+)
 create mode 100644 m4/ax_cc_for_build.m4

diff --git a/Makefile.am b/Makefile.am
index 4468bca..bd3ce01 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -2,6 +2,7 @@ AM_CFLAGS = -Isrc -fPIC -Wall -O3 -lm
 AUTOMAKE_OPTIONS = gnu 
 NAME = codec2
 AM_CPPFLAGS = $(AM_CFLAGS)
+ACLOCAL_AMFLAGS = -I m4
 
 pkgconfigdir = $(libdir)/pkgconfig
 pkgconfig_DATA = codec2.pc
diff --git a/configure.ac b/configure.ac
index 493c517..7520af6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -4,10 +4,12 @@
 AC_PREREQ([2.59])
 AC_INIT(codec2, 0.2, david@rowetel.com)
 AM_INIT_AUTOMAKE
+AC_CONFIG_MACRO_DIR([m4])
 
 # Checks for programs.
 AC_PROG_CC
 AC_PROG_LIBTOOL
+AX_CC_FOR_BUILD
 
 # Checks for libraries.
 # FIXME: Replace `main' with a function in `-lm':
diff --git a/m4/ax_cc_for_build.m4 b/m4/ax_cc_for_build.m4
new file mode 100644
index 0000000..c880fd0
--- /dev/null
+++ b/m4/ax_cc_for_build.m4
@@ -0,0 +1,77 @@
+# ===========================================================================
+#      http://www.gnu.org/software/autoconf-archive/ax_cc_for_build.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AX_CC_FOR_BUILD
+#
+# DESCRIPTION
+#
+#   Find a build-time compiler. Sets CC_FOR_BUILD and EXEEXT_FOR_BUILD.
+#
+# LICENSE
+#
+#   Copyright (c) 2010 Reuben Thomas <rrt@sc3d.org>
+#   Copyright (c) 1999 Richard Henderson <rth@redhat.com>
+#
+#   This program is free software: you can redistribute it and/or modify it
+#   under the terms of the GNU General Public License as published by the
+#   Free Software Foundation, either version 3 of the License, or (at your
+#   option) any later version.
+#
+#   This program 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 a copy of the GNU General Public License along
+#   with this program. If not, see <http://www.gnu.org/licenses/>.
+#
+#   As a special exception, the respective Autoconf Macro's copyright owner
+#   gives unlimited permission to copy, distribute and modify the configure
+#   scripts that are the output of Autoconf when processing the Macro. You
+#   need not follow the terms of the GNU General Public License when using
+#   or distributing such scripts, even though portions of the text of the
+#   Macro appear in them. The GNU General Public License (GPL) does govern
+#   all other use of the material that constitutes the Autoconf Macro.
+#
+#   This special exception to the GPL applies to versions of the Autoconf
+#   Macro released by the Autoconf Archive. When you make and distribute a
+#   modified version of the Autoconf Macro, you may extend this special
+#   exception to the GPL to apply to your modified version as well.
+
+#serial 2
+
+dnl Get a default for CC_FOR_BUILD to put into Makefile.
+AC_DEFUN([AX_CC_FOR_BUILD],
+[# Put a plausible default for CC_FOR_BUILD in Makefile.
+if test -z "$CC_FOR_BUILD"; then
+  if test "x$cross_compiling" = "xno"; then
+    CC_FOR_BUILD='$(CC)'
+  else
+    CC_FOR_BUILD=gcc
+  fi
+fi
+AC_SUBST(CC_FOR_BUILD)
+# Also set EXEEXT_FOR_BUILD.
+if test "x$cross_compiling" = "xno"; then
+  EXEEXT_FOR_BUILD='$(EXEEXT)'
+else
+  AC_CACHE_CHECK([for build system executable suffix], bfd_cv_build_exeext,
+    [rm -f conftest*
+     echo 'int main () { return 0; }' > conftest.c
+     bfd_cv_build_exeext=
+     ${CC_FOR_BUILD} -o conftest conftest.c 1>&5 2>&5
+     for file in conftest.*; do
+       case $file in
+       *.c | *.o | *.obj | *.ilk | *.pdb) ;;
+       *) bfd_cv_build_exeext=`echo $file | sed -e s/conftest//` ;;
+       esac
+     done
+     rm -f conftest*
+     test x"${bfd_cv_build_exeext}" = x && bfd_cv_build_exeext=no])
+  EXEEXT_FOR_BUILD=""
+  test x"${bfd_cv_build_exeext}" != xno && EXEEXT_FOR_BUILD=${bfd_cv_build_exeext}
+fi
+AC_SUBST(EXEEXT_FOR_BUILD)])dnl
diff --git a/src/Makefile.am b/src/Makefile.am
index 1153b3c..719088d 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -77,6 +77,9 @@ CODEBOOKSGE= \
 
 noinst_PROGRAMS = generate_codebook genlspdtcb
 
+generate_codebook$(EXEEXT_FOR_BUILD): generate_codebook.c
+	$(CC_FOR_BUILD) -o $@ generate_codebook.c -lm
+
 codebook.$(OBJEXT): codebook.c
 codebookd.$(OBJEXT): codebookd.c
 codebookdt.$(OBJEXT): codebookdt.c
-- 
2.5.0