| T.R | Title | User | Personal
Name | Date | Lines |
|---|
| 8841.1 | why do you want to do this? | VAXCPU::michaud | Jeff Michaud - ObjectBroker | Fri Feb 14 1997 21:54 | 7 |
| Why don't you explain why you want to do this and we can
proceed from there.
The only supported (and relatively portable, at least to
other UNIX platforms) way I know of to recover from a
SEGV or BUS error is to use setjmp and then longjmp from
the signal handler.
|
| 8841.2 | sc_pc in sig_context structure | STEVEN::hobbs | Steven Hobbs | Sat Feb 15 1997 17:46 | 14 |
| The -speculate optimization option on the various compiler command
lines uses an additional supported way to continue after a SEGV or BUS
error but that is probably no useful in the current situation.
I often write code that continues from FPE faults. All I need to do
is increment by 4 the sc_pc field in the sig_context structure before
returning from the signal handler.
Note: I must be careful when continuing from FPE signals since some
signals are faults and others others are traps. Only the faults need
sc_pc incremented. On Unix, both SEGV and BUS are faults but if you
are writing code that will run on both Unix and VMS then you should be
careful. I believe that the BUS exceptions on VMS caused by
misaligned memory references are synchronous traps rather than faults.
|
| 8841.3 | | CADSYS::BOGDANOV | | Mon Feb 17 1997 13:16 | 15 |
| .1
> Why don't you explain why you want to do this and we can
> proceed from there.
I need a memory probe mechanism where request, address and data is
known to the program. I can analyze a current instruction to see whwt is going
on. Then the program should continue, returning normally from a handler.
.2
Thank you for an idea. I did not expect that incrementing pc in the
sig_context is going to work but looks like it does. Is it a reliable mechanism
on Dunix?
>> Serge
|
| 8841.4 | sigreturn | CADSYS::BOGDANOV | | Mon Feb 17 1997 17:32 | 22 |
| I think that I've found an answer in man pages. The sigreturn routine should be
able to help.
#include <signal.h>
int sigreturn(
struct sigcontext *scp) ;
PARAMETERS
scp Points to a sigcontext structure whose members contain the pro-
cessor state to be restored. The contents of the sigcontext
structure should have been previously obtained by entry to a sig-
nal handler or by the setjmp() or sigsetjmp() function.
DESCRIPTION
The sigreturn() function restores the processor state of the calling pro-
cess from a sigcontext structure...
Thanks
>> Serge
|