Re: [PATCH] remove target_os

[Christian Franke]

Robert Millan wrote:
> Hi,
>
> Based on the description of host/target triplets in configure.ac:
>
> dnl   build  -- the environment for building GRUB
> dnl   host   -- the environment for running utilities
> dnl   target -- the environment for running GRUB
>
> it seems that target_os is an oxymoron.  There's no OS in the environment
> where GRUB will run (well, there's the firmware, but we already use
> target_vendor for that, and _os has a well-defined meaning).
>
> Attached patch fixes that by supressing all references to target_os, and
> replacing them with host_os where suitable.
>
> Christian: since this mostly affects Cygwin, could you verify that it doesn't
> cause breakage before I commit it?
>
>   

Hi Robert,

thanks for sending the patch first. Cygwin build looks good.


But even if GRUB itself is build for some $target_cpu-$target_vendor 
(i386-pc), the target_os is not useless if cross-compilation support is 
desired:

- GRUB tools like grub-setup are build for the target_os
- Package structure may depend on target_os.

- The gcc code generator may emit special code tailored for the assumed 
target_os
Examples:
Stack frame checks
Nested function trampolines (__enable_execute_stack())

Unfortunately, gcc has no '-fno_os' option to specify the bare CPU as 
target.
Fortunately, all current issues can be handled by autoconf checks.


>  AC_MSG_CHECKING([for command to convert module to ELF format])
> -case "${host_os}:${target_os}" in
> -  cygwin:cygwin) TARGET_OBJ2ELF='grub-pe2elf' ;;
> +case "${host_os}" in
> +  cygwin) TARGET_OBJ2ELF='grub-pe2elf' ;;
>    *) ;;
>  esac
>   

This won't work for a Linux cross compiler hosted on Cygwin. It would 
emit ELF format and does not need pe2elf.

But all this is theoretical unless cross compilation is really needed.

Christian