b18: cygwin_except_handler failure on deref NULL

b18: cygwin_except_handler failure on deref NULL

[Steven Pemberton]

I have a program that generates limits.h and float.h. It is also an
extremely good compiler tester. You can find it at:

	http://www.cwi.nl/~steven/enquire.html

An earlier version is part of the gcc distribution and apparently was
used to generate the float.h include file of b18.

Compiling and running it with b18 causes a run-time failure (and bash
hangs) with the message:

	(ENQUIRE.EXE 1011) In cygwin_except_handler

I don't know what the 1011 refers to, but if it's a line number, that
is not where it failed.

It failed at the point where the program looks to see if dereferencing
NULL causes a trap (which is done using setjmp, and dereferencing NULL).

Steven Pemberton, CWI, Amsterdam; Steven.Pemberton@cwi.nl
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RE: b18: cygwin_except_handler failure on deref NULL

[dahms]

Hi Steven, you wrote:

: 	(ENQUIRE.EXE 1011) In cygwin_except_handler

: It failed at the point where the program looks to see if dereferencing
: NULL causes a trap (which is done using setjmp, and dereferencing NULL).

I think it worked, because cygwin_except_handler *is* the trap handler!
Do you have an complete example in a dozen of source lines or so?


Bye, Heribert (dahms@ifk20.mach.uni-karlsruhe.de)
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RE: b18: cygwin_except_handler failure on deref NULL

[Steven Pemberton]

 > Hi Steven, you wrote:
 > 
 > : 	(ENQUIRE.EXE 1011) In cygwin_except_handler
 > 
 > : It failed at the point where the program looks to see if dereferencing
 > : NULL causes a trap (which is done using setjmp, and dereferencing NULL).
 > 
 > I think it worked, because cygwin_except_handler *is* the trap handler!
 > Do you have an complete example in a dozen of source lines or so?

My guess is that this would cause the same fault (but I don't have a
PC to hand):

#include <stdio.h>
#include <signal.h>
#include <setjmp.h>

jmp_buf mlab; int v, *p;

void address(sig) int sig; { /* what to do on an address error */
  signal(sig, address);
  longjmp(mlab, 1);
}

main() {
#ifdef SIGBUS
	signal(SIGBUS, address);
#endif
#ifdef SIGSEGV
	signal(SIGSEGV, address);
#endif
	if (setjmp(mlab) == 0) {
		p= 0;
		v= *p;
		printf("Dereferencing NULL doesn't cause a trap\n");
	} else {
		printf("Dereferencing NULL causes a trap\n");
	}
}

Best wishes,

Steven Pemberton
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