build: support cross compiling.

Check for cross compiling. If cross compiling, build stage1flex using a
custom link command.
We also override LDADD since that adds the replacement implementations
that are cross compiled, and instead always use the replacement library
implementations.

We don't use BUILD_OBJEXT and BUILD_EXEEXT since it seems that automake
does not support these.

Fixes #78.

configure.ac

@@ -47,6 +47,7 @@ AS_IF([test "$YACC" != 'bison -y'], [
 AM_CONDITIONAL([HAVE_BISON], [test "$YACC" = 'bison -y'])
 AM_PROG_LEX
 AC_PROG_CC
+AX_PROG_CC_FOR_BUILD
 AC_PROG_CXX
 AM_PROG_CC_C_O
 AC_PROG_LN_S
@@ -80,6 +81,8 @@ AC_ARG_ENABLE([bootstrap],
   [], [enable_bootstrap=yes])
 AM_CONDITIONAL([ENABLE_BOOTSTRAP], [test "x$enable_bootstrap" = xyes])
 
+AM_CONDITIONAL([CROSS], [test "x$cross_compiling" = xyes])
+
 AC_PATH_PROG([HELP2MAN], help2man, [\${top_srcdir}/build-aux/missing help2man])
   AS_IF([test "$HELP2MAN" = "\${top_srcdir}/build-aux/missing help2man"],
     AC_MSG_WARN(help2man: program not found: building man page will not work)

m4/ax_prog_cc_for_build.m4

@@ -0,0 +1,125 @@
+# ===========================================================================
+#   http://www.gnu.org/software/autoconf-archive/ax_prog_cc_for_build.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AX_PROG_CC_FOR_BUILD
+#
+# DESCRIPTION
+#
+#   This macro searches for a C compiler that generates native executables,
+#   that is a C compiler that surely is not a cross-compiler. This can be
+#   useful if you have to generate source code at compile-time like for
+#   example GCC does.
+#
+#   The macro sets the CC_FOR_BUILD and CPP_FOR_BUILD macros to anything
+#   needed to compile or link (CC_FOR_BUILD) and preprocess (CPP_FOR_BUILD).
+#   The value of these variables can be overridden by the user by specifying
+#   a compiler with an environment variable (like you do for standard CC).
+#
+#   It also sets BUILD_EXEEXT and BUILD_OBJEXT to the executable and object
+#   file extensions for the build platform, and GCC_FOR_BUILD to `yes' if
+#   the compiler we found is GCC. All these variables but GCC_FOR_BUILD are
+#   substituted in the Makefile.
+#
+# LICENSE
+#
+#   Copyright (c) 2008 Paolo Bonzini <bonzini@gnu.org>
+#
+#   Copying and distribution of this file, with or without modification, are
+#   permitted in any medium without royalty provided the copyright notice
+#   and this notice are preserved. This file is offered as-is, without any
+#   warranty.
+
+#serial 8
+
+AU_ALIAS([AC_PROG_CC_FOR_BUILD], [AX_PROG_CC_FOR_BUILD])
+AC_DEFUN([AX_PROG_CC_FOR_BUILD], [dnl
+AC_REQUIRE([AC_PROG_CC])dnl
+AC_REQUIRE([AC_PROG_CPP])dnl
+AC_REQUIRE([AC_EXEEXT])dnl
+AC_REQUIRE([AC_CANONICAL_HOST])dnl
+
+dnl Use the standard macros, but make them use other variable names
+dnl
+pushdef([ac_cv_prog_CPP], ac_cv_build_prog_CPP)dnl
+pushdef([ac_cv_prog_gcc], ac_cv_build_prog_gcc)dnl
+pushdef([ac_cv_prog_cc_works], ac_cv_build_prog_cc_works)dnl
+pushdef([ac_cv_prog_cc_cross], ac_cv_build_prog_cc_cross)dnl
+pushdef([ac_cv_prog_cc_g], ac_cv_build_prog_cc_g)dnl
+pushdef([ac_cv_exeext], ac_cv_build_exeext)dnl
+pushdef([ac_cv_objext], ac_cv_build_objext)dnl
+pushdef([ac_exeext], ac_build_exeext)dnl
+pushdef([ac_objext], ac_build_objext)dnl
+pushdef([CC], CC_FOR_BUILD)dnl
+pushdef([CPP], CPP_FOR_BUILD)dnl
+pushdef([CFLAGS], CFLAGS_FOR_BUILD)dnl
+pushdef([CPPFLAGS], CPPFLAGS_FOR_BUILD)dnl
+pushdef([LDFLAGS], LDFLAGS_FOR_BUILD)dnl
+pushdef([host], build)dnl
+pushdef([host_alias], build_alias)dnl
+pushdef([host_cpu], build_cpu)dnl
+pushdef([host_vendor], build_vendor)dnl
+pushdef([host_os], build_os)dnl
+pushdef([ac_cv_host], ac_cv_build)dnl
+pushdef([ac_cv_host_alias], ac_cv_build_alias)dnl
+pushdef([ac_cv_host_cpu], ac_cv_build_cpu)dnl
+pushdef([ac_cv_host_vendor], ac_cv_build_vendor)dnl
+pushdef([ac_cv_host_os], ac_cv_build_os)dnl
+pushdef([ac_cpp], ac_build_cpp)dnl
+pushdef([ac_compile], ac_build_compile)dnl
+pushdef([ac_link], ac_build_link)dnl
+
+save_cross_compiling=$cross_compiling
+save_ac_tool_prefix=$ac_tool_prefix
+cross_compiling=no
+ac_tool_prefix=
+
+AC_PROG_CC
+AC_PROG_CPP
+AC_EXEEXT
+
+ac_tool_prefix=$save_ac_tool_prefix
+cross_compiling=$save_cross_compiling
+
+dnl Restore the old definitions
+dnl
+popdef([ac_link])dnl
+popdef([ac_compile])dnl
+popdef([ac_cpp])dnl
+popdef([ac_cv_host_os])dnl
+popdef([ac_cv_host_vendor])dnl
+popdef([ac_cv_host_cpu])dnl
+popdef([ac_cv_host_alias])dnl
+popdef([ac_cv_host])dnl
+popdef([host_os])dnl
+popdef([host_vendor])dnl
+popdef([host_cpu])dnl
+popdef([host_alias])dnl
+popdef([host])dnl
+popdef([LDFLAGS])dnl
+popdef([CPPFLAGS])dnl
+popdef([CFLAGS])dnl
+popdef([CPP])dnl
+popdef([CC])dnl
+popdef([ac_objext])dnl
+popdef([ac_exeext])dnl
+popdef([ac_cv_objext])dnl
+popdef([ac_cv_exeext])dnl
+popdef([ac_cv_prog_cc_g])dnl
+popdef([ac_cv_prog_cc_cross])dnl
+popdef([ac_cv_prog_cc_works])dnl
+popdef([ac_cv_prog_gcc])dnl
+popdef([ac_cv_prog_CPP])dnl
+
+dnl Finally, set Makefile variables
+dnl
+BUILD_EXEEXT=$ac_build_exeext
+BUILD_OBJEXT=$ac_build_objext
+AC_SUBST(BUILD_EXEEXT)dnl
+AC_SUBST(BUILD_OBJEXT)dnl
+AC_SUBST([CFLAGS_FOR_BUILD])dnl
+AC_SUBST([CPPFLAGS_FOR_BUILD])dnl
+AC_SUBST([LDFLAGS_FOR_BUILD])dnl
+])

src/Makefile.am

@@ -21,7 +21,24 @@ stage1flex_SOURCES = \
 	scan.l \
 	$(COMMON_SOURCES)
 
+if CROSS
+stage1flex_LDADD =
+stage1flex_SOURCES += \
+		      ../lib/malloc.c \
+		      ../lib/realloc.c
+stage1flex_LINK = $(LIBTOOL) --tag=CC --mode=link $(CC_FOR_BUILD) \
+		  $(CFLAGS_FOR_BUILD) $(LDFLAGS_FOR_BUILD) -o $@
+
+$(stage1flex_OBJECTS): CC=$(CC_FOR_BUILD)
+$(stage1flex_OBJECTS): CFLAGS=$(CFLAGS_FOR_BUILD)
+$(stage1flex_OBJECTS): CPP=$(CPP_FOR_BUILD)
+$(stage1flex_OBJECTS): CPPFLAGS=$(CPPFLAGS_FOR_BUILD)
+$(stage1flex_OBJECTS): LDFLAGS=$(LDFLAGS_FOR_BUILD)
+else
+stage1flex_LDADD = $(LDADD)
+stage1flex_LINK = $(LINK)
 stage1flex_CFLAGS = $(AM_CFLAGS)
+endif
 
 flex_SOURCES = \
 	$(COMMON_SOURCES)