El mar, 27-01-2009 a las 20:56 +0100, Christian Franke escribió: > Javier Martín wrote: > > El mar, 27-01-2009 a las 18:21 +0100, Christian Franke escribió: > > > >> Javier Martín wrote: > >> > >>>> Unfortunately, gcc has no '-fno_os' option to specify the bare CPU as > >>>> target. > >>>> > >>>> > >>> Might -ffreestanding be what you are looking for? > >>> > >>> > >>> > >> The option '-ffreestanding' is the same as '-fno-hosted'. > >> > >> According to gcc (4.3.1) source, '-fno-hosted' clears variable > >> 'flag_hosted' and sets '-fno-builtin'. The latter is already set within > >> GRUB build. > >> > >> A cleared 'flag_hosted' apparently has only 2 effects: > >> - disable the special handling of 'main()'. > >> - #define __STDC_HOSTED__ to 0 instead of 1 > >> > >> There is no effect on the target_os dependent parts of the gcc code > >> generation. For example, on i386, __enable_execute_stack() calls are > >> generated for target_os netbsd, openbsd and cygwin, but not for linux. > >> The emit call is hard-coded in > >> gcc/configs/i386/i386.c:x86_initialize_trampoline(). > >> > > > > In that case, we are dealing with a GCC bug. We might want to require > > the user to create a bare "no-OS" cross compiler. > > > > > > Is building a bare 'no-OS' compiler supported by the upstream GCC sources? > Probably a too strict prerequisite for building GRUB.
I can't vouch so for all possible environments, but I can say that "clean" no-OS targets like i386-pc-elf exist at least for x86 and x86_64 (this last being added as of GCC 4.3.2). However, as I said, if -ffreestanding does not do its job of providing a "true" freestanding environment (i.e. without relying on _any_ external libraries or syscalls, as opposite to the usual hosted environment), a bug report should be posted.
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