Cross-compilation

[Ladislav Michl]

Hi there,

I'm considering gnustep-make to be a (cross)tool, similar binutils is, which
seems to match chapter '1.2.5 Configuring for a cross-compile target' of the
INSTALL file:
https://github.com/gnustep/tools-make/blob/master/INSTALL#L154

However running
./configure --target=arm-v7a-linux-gnueabi
gives:
checking build system type... x86_64-pc-linux-gnu
checking host system type... x86_64-pc-linux-gnu
checking target system type... arm-v7a-linux-gnueabi
checking for pkgconfig... yes
checking for library combo... gnu-gnu-gnu
checking for gcc... gcc
checking whether the C compiler works... yes
checking for C compiler default output file name... a.out
checking for suffix of executables... 
checking whether we are cross compiling... no
checking for suffix of object files... o
checking whether we are using the GNU C compiler... yes
checking whether gcc accepts -g... yes
checking for gcc option to accept ISO C89... none needed
checking how to run the C preprocessor... gcc -E
checking for g++... g++
checking whether we are using the GNU C++ compiler... yes
checking whether g++ accepts -g... yes
checking for grep that handles long lines and -e... /usr/bin/grep
checking for egrep... /usr/bin/grep -E
checking for apple compiler flags... yes
cross compiling from x86_64-pc-linux-gnu to arm-v7a-linux-gnueabi ..
checking for arm-v7a-linux-gnueabi-gcc... gcc
checking for arm-v7a-linux-gnueabi-ranlib... arm-v7a-linux-gnueabi-ranlib
checking for arm-v7a-linux-gnueabi-ar... arm-v7a-linux-gnueabi-ar
checking for arm-v7a-linux-gnueabi-dlltool... dlltool

As you can see ggc is still host gcc which later gives for gnustep-base
(that is a target package):
./configure --build=x86_64-host-linux-gnu --host=arm-v7a-linux-gnueabi
checking build system type... x86_64-host-linux-gnu
checking host system type... arm-v7a-linux-gnueabi
checking target system type... arm-v7a-linux-gnueabi
...
configure: WARNING: You are running configure with the compiler 
(arm-v7a-linux-gnueabi-gcc) set to a different value from that used by 
gnustep-make (gcc).  To avoid conflicts/problems, reconfigure/reinstall 
gnustep-make to use CC=arm-v7a-linux-gnueabi-gcc or run the gnustep-base 
configure again with your CC environment variable set to gcc
configure: WARNING: You are running configure with the preprocessor 
(arm-v7a-linux-gnueabi-gcc -E) set to a different value from that used by 
gnustep-make (gcc -E).  To avoid conflicts/problems, reconfigure/reinstall 
gnustep-make to use CPP=arm-v7a-linux-gnueabi-gcc -E or run the gnustep-base 
configure again with your CPP environment variable set to gcc -E
configure: WARNING: You are running configure with the compiler 
(arm-v7a-linux-gnueabi-g++) set to a different value from that used by 
gnustep-make (g++).  To avoid conflicts/problems, reconfigure/reinstall 
gnustep-make to use CXX=arm-v7a-linux-gnueabi-g++ or run the gnustep-base 
configure again with your CXX environment variable set to g++
checking for arm-v7a-linux-gnueabi-gcc... arm-v7a-linux-gnueabi-gcc
checking whether the C compiler works... yes
checking for C compiler default output file name... a.out
checking for suffix of executables... 
checking whether we are cross compiling... yes

Later compilation fails, which is somewhat expected.

Looking at gnustep-tools' configure.ac native compiler is set first
(see also above that line):
https://github.com/gnustep/tools-make/blob/master/configure.ac#L119
here setting CC basically prevents later checks from doing its job:
https://github.com/gnustep/tools-make/blob/master/configure.ac#L236
Also configure.ac contains a lot of ancient stuff for apple, cygwin
and mingw, which seems quite fragile to touch, so minimal fix could
look like:

diff --git a/configure.ac b/configure.ac
index 773bf313..ec45aec4 100644
--- a/configure.ac
+++ b/configure.ac
@@ -236,6 +236,7 @@ fi
 if test "x$target" != "x$host"; then
   echo "cross compiling from $host to $target .."
   cross_compiling="yes"
+  export CC=
   if test "$OBJC_RUNTIME_LIB" = ng; then
     AC_CHECK_PROG(CC,    "${targetArgument}-clang",   dnl
                          "${targetArgument}-clang",   clang)

Questions are:
- How is GNUstep supposed to be crosscompiled?
- Is there a list of tested targets?

Thank you,
        ladis