Re: [PATCH]: Fix PR19061, gdb hangs/spins-on-cpu when debugging any program on Alpha

[Simon Marchi <simon.marchi@polymtl.ca>]

On 2018-05-31 05:23, Uros Bizjak wrote:
> On Wed, May 30, 2018 at 4:53 PM, Simon Marchi 
> <simon.marchi@ericsson.com> wrote:
>> Does Alpha even have hardware breakpoints?  If not, I would suggest
>> defining GDB_ARCH_IS_TRAP_HWBKPT to 0 for __alpha__.  It would get
>> rid of the error, and be more exact (no si_code can mean "hardware
>> breakpoint" on alpha).
> 
> I didn't find any mentions of hardware breakpoint support in Alpha
> Architecture Handbook v.4.
> 
> Please note that save_stop_reason from linux-nat.c has some code to
> detect ambigous si_code, where si_code is both TRAP_BRKPT and
> TRAP_HWBKPT, and returns TARGET_STOPPED_BY_SW_BREAKPOINT in this case.
> So, if we don't define anything for __alpha__ in nat/linux-ptrace.h,
> we get the same result.

TRAP_BKPT and TRAP_HWBKPT are different, so this will never happen with 
the default definitions of 
GDB_ARCH_IS_TRAP_BRKPT/GDB_ARCH_IS_TRAP_HWBKPT.  Since the kernel for 
alpha never sets si_code to TRAP_HWBKPT, it means we'll never get in to 
the HW breakpoint branch, which is fine.

In short, the patch LGTM.

> I have tested the attached patch, and resulting gdb works OK for me.

Thanks!

Simon