Re: [patch/rfc,rfa:ppc64] Add osabi wildcard support

[Kevin Buettner <kevinb@redhat.com>]

On Oct 23,  7:25pm, Andrew Cagney wrote:

> The attached patch adds the ability to specify a wildcard machine when 
> registering an OSABI / arch / machine.  It then updates PPC64 GNU/Linux 
> to specify that wild card (-1) instead of zero as the default machine.
> 
> Looking at the PPC64 GNU/Linux code:
> 
>    gdbarch_register_osabi (bfd_arch_powerpc, 0, GDB_OSABI_LINUX,
>                            ppc_linux_init_abi);
> 
> I believe that the call is attempting to register ppc_linux_init_abi as 
> the OSABI handler for all arch/machine conbinations.  The problem is 
> that machine "0" gets turned into bfd_mach_ppc or bfd_mach_ppc64 
> dependant on how GDB is built, and they are both incompatible with each 
> other and incompatible .  And that in turn restricts the support to just 
> one half of the ISA family making it impossible for GDB to debug both 32 
> and 64 bit :-(
> 
> I know of two ways to fix this.  First is the attached patch which 
> modifies osabi.[hc] so that a wildcard machine (-1) can be specified vis:
> 
>    gdbarch_register_osabi (bfd_arch_powerpc, -1, GDB_OSABI_LINUX,
>                            ppc_linux_init_abi);
> 
> and the second is to explicitly register both of these architecture 
> variants vis:
> 
>    gdbarch_register_osabi (bfd_arch_powerpc, bfd_mach_ppc, ...
>    gdbarch_register_osabi (bfd_arch_powerpc, bfd_mach_ppc64, ...
> 
> (possibly also splitting ppc_linux_init_abi into ppc_linux_init_abi_32 
> and ppc_linux_init_abi_32).
> 
> There are pros and cons to both.
> 
> The former will always match, making the code somewhat future proof, the 
> later is far simplier.
> 
> preferences?

At the moment, I prefer the explicit registration of architecture
variants.  I'd prefer to wait on adding the wildcard mechanism until a
more compelling need for it is demonstrated.

Kevin