Re: MIPS Linux signals

[Pedro Alves <palves@redhat.com>]

On 05/22/2012 07:14 PM, Michael Eager wrote:

> On 05/22/2012 09:01 AM, Pedro Alves wrote:
> 
>>>> target_signal_from_host =>   gdb_signal_from_host (or gdb_signal_from_host_signal)
>>>> target_signal_to_host =>   gdb_signal_to_host (or gdb_signal_to_host_signal)
>>>>
>>>> gdbarch_target_signal_from_host =>   gdbarch_gdb_signal_from_target (or gdbarch_gdb_signal_from_target_signal)
>>>> gdbarch_target_signal_to_host =>   gdbarch_gdb_signal_to_target (or gdbarch_gdb_signal_to_target_signal)
>>>
>>> OK, but I'd recommend
>>>    target_signal_from_host =>   gdb_signal_from_target
>>>    target_signal_to_host =>   gdb_signal_to_target
>>>
>>> This is symmetric with the gdbarch_ functions and clear that the function
>>> translates to/from target system values, not the host system.
>>
>>


>> But it's not what the functions do...  They really convert from the host
>> system signals, not the target's.  I think the symmetry will only lead to
>> people getting confused (which one to call in common/target-independent code?).
> 
> If you are running GDB on a Windows host, for example, what host
> system signals are you translating?


There's only be one such call -- the one from within corelow.c, if there's no
gdbarch_target_signal_from_host callback installed.  (The Windows ports don't call
target_signal_from_host anywhere (windows-nat.c and friends).  And in that case, if
you e.g., load a cygwin core, the target_signal_from_host fallback will try to
convert the signal number as if it was a host signal number.  If you're running g
b on a cygwin host, you'll happen to get the right values.  If you're debugging
a core (that same core or of some other non-native arch) with a cross debugger, with
a mingw hosted gdb, then target_signal_from_host will _still_ translate the signal
numbers found in mingw's signal.h header.  For reference, those are:

#define SIGINT          2       /* Interactive attention */
#define SIGILL          4       /* Illegal instruction */
#define SIGFPE          8       /* Floating point error */
#define SIGSEGV         11      /* Segmentation violation */
#define SIGTERM         15      /* Termination request */
#define SIGBREAK        21      /* Control-break */
#define SIGABRT         22      /* Abnormal termination (abort) */

All other signal numbers you pass to target_signal_from_host will end up
as TARGET_SIGNAL_UNKNOWN, due to the bunch of #ifdef SIGFOO bits in
common/signals.  Obviously, in most cases, this translation will
be wrong.  But the point to be taken is, target_signal_from_host _always_
translates the signal number passed as argument as if it was a host
signal number, no matter what the target really is.

-- 
Pedro Alves