topic Re: Porting from TRU64: structured exception handling in Operating System - HP-UX

Porting from TRU64: structured exception handling

arunava — Wed, 25 Mar 2009 13:47:16 GMT

Hi All,
I am migrating an application from TRU64 to HPUX. The source includes excpt.h and uses the function "exc_raise_signal_exception" as a signal handler for SIGSEGV. HP UX doesnt have this header file. Can any one pls guide me what is the alternative. One alternative could be writing a custom signal handler that throws exceptions.
Thanks in advance .....

Re: Porting from TRU64: structured exception handling

Dennis Handly — Wed, 25 Mar 2009 19:19:21 GMT

This doesn't exist on HP-UX.

>could be writing a custom signal handler that throws exceptions.

Also the C++ Standard doesn't support throwing from a signal handler. While not disallowed by the aC++ runtime, the results are unpredictable.

Re: Porting from TRU64: structured exception handling

arunava — Thu, 26 Mar 2009 21:08:47 GMT

Hi Dennis,
Thanks for the reply. Seems I need to take out the signal handling out of the existing code. Also, I need to compile the source for Itanium. I also read your article : http://h21007.www2.hp.com/portal/site/dspp/menuitem.863c3e4cbcdc3f3515b49c108973a801?ciid=c5080055abe021100055abe02110275d6e10RCRD
Acc to your article, throwing out of a signal handler is not at all possible on itanium.

So was wondering, is there any other way I can simulate the functionality on hp ux. Will try this: catch the signal, set a flag and return from the signal handler. And based on the flag throw an exception. Will try to code this and post the results.

Re: Porting from TRU64: structured exception handling

Dennis Handly — Fri, 27 Mar 2009 06:26:13 GMT

>Seems I need to take out the signal handling out of the existing code.

That's the only way to be supported.

>I need to compile the source for Integrity.

Things have changed since that was first written but it is still unsupported.
I guess it depends on close you want to skate to thin ice. ;-)

>is there any other way I can simulate the functionality on HP-UX? Will try this: catch the signal, set a flag and return from the signal handler.

No. Only by trying a throw and hope your opt level, where it aborts isn't too high.
Otherwise if you return you will get the trap again.

Re: Porting from TRU64: structured exception handling

arunava — Fri, 27 Mar 2009 12:49:45 GMT

Hi Dennis,
I tried writing the following code with setjmp/longjmp. Assuming that I call the setjmp/longjump at the correct places, what other dangers could happen with this code. Thanks again for the replies ....
--------------------------------------
#include
#include
#include

int error=0;
jmp_buf jbuff;

struct sigaction foo;

void hand_x(int sig, siginfo_t *siginf, void *ptr){
printf("inside hanldler\n");
error =1;
longjmp(jbuff,sig);
}

main()
{
struct sigaction foo = {hand_x,0,0};
sigaction(SIGSEGV,&foo,0);
char * a= "hello";
try
{
setjmp(jbuff);
if(error == 1)
throw 1;
a[10]='a'; //Segmentation fault here
}
catch(...)
{
printf("exception raised\n");
}
}

Re: Porting from TRU64: structured exception handling

Dennis Handly — Fri, 27 Mar 2009 22:48:00 GMT

>I tried writing the following code with setjmp/longjmp.

If you read the Release Notes, you'll also find that's not supported either with C++.
http://docs.hp.com/en/B3901-90031/ch05s08.html#v2649446
http://docs.hp.com/en/B3901-90031/ch05s08.html#v2649455

Your variable "error" isn't volatile and since setjmp returns a value, you should test that and not "error".

Re: Porting from TRU64: structured exception handling

arunava — Mon, 30 Mar 2009 14:07:08 GMT

Hi Dennis, thanks for all the replies.
We are removing the signal handling from code, although this means at runtime we are going to get lots of dumps !!

Re: Porting from TRU64: structured exception handling

Dennis Handly — Mon, 30 Mar 2009 23:11:21 GMT

>although this means at runtime we are going to get lots of dumps!

Do you know why you have bad pointers?

Re: Porting from TRU64: structured exception handling

arunava — Tue, 14 Apr 2009 09:34:08 GMT

Hi ..

>>Do you know why you have bad pointers?
No .. Even going through the tons of source doesnt help.. I guess we have to fix the cause of the dumps as and when we get them.

Thanks a lot ..

Re: Porting from TRU64: structured exception handling

Dennis Handly — Tue, 14 Apr 2009 10:42:28 GMT

>I guess we have to fix the cause of the dumps as and when we get them.

You didn't fix these completely when running under Tru64?

Re: Porting from TRU64: structured exception handling

arunava — Tue, 14 Apr 2009 10:57:02 GMT

On TRU64, the signals (SIGSEGV) were converted to exceptions using the function "exc_raise_signal_exception". And there are huge try..catch blocks that i hav been trying to understand. Also, the code is written by guys who are no longer around. So I cant know in which part of the code or in what scenario, was the programmer expecting the signal. So will try to run and hope I find all causes of the signal.

Re: Porting from TRU64: structured exception handling

Dennis Handly — Tue, 14 Apr 2009 11:17:02 GMT

Are you suggesting that the program got those signals all of the time? Or that try/catch was just for belts and suspenders type of programming?

Re: Porting from TRU64: structured exception handling

arunava — Tue, 14 Apr 2009 11:38:48 GMT

>>Are you suggesting that the program got those signals all of the time?
Yes I think so ...
>>Or that try/catch was just for belts and suspenders type of programming?
Not sure about this. Could be a third party lib that caused lots of sigsegv. So .. as of now going through the code .... Thanks for all the help ...