* bug in stackchk.h
@ 2010-01-06 21:37 Ivan Shcherbakov
2010-01-17 21:44 ` Neil Jerram
0 siblings, 1 reply; 3+ messages in thread
From: Ivan Shcherbakov @ 2010-01-06 21:37 UTC (permalink / raw)
To: bug-guile
Hi, All,
There is a bug in libguile/stackchk.h file. In some cases, when
integer value of the stack pointer is less than stack checking limit,
false positives are produced.
The following code is responsible for the problem:
# define SCM_STACK_OVERFLOW_P(s)\
(SCM_STACK_PTR (s) \
< (SCM_I_CURRENT_THREAD->base - SCM_STACK_LIMIT))
When SCM_I_CURRENT_THREAD->base < SCM_STACK_LIMIT holds,
the last part of the exception produces an overflow and the entire
expression holds even when no stack overflow occurs.
To fix the problem, the SCM_STACK_OVERFLOW() should be replaced by the
following one:
# define SCM_STACK_OVERFLOW_P(s)\
((SCM_I_CURRENT_THREAD->base - SCM_STACK_PTR (s)) \
> SCM_STACK_LIMIT)
This ensures that the difference between the stack base and the
examined local variable address is always computed correctly
regardless the integer value of the stack pointer.
--
Best Regards,
Ivan Shcherbakov mailto:shcherbakov@eit.uni-kl.de
TU Kaiserslautern, Germany
Department of Real-Time Systems
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: bug in stackchk.h
2010-01-06 21:37 bug in stackchk.h Ivan Shcherbakov
@ 2010-01-17 21:44 ` Neil Jerram
2010-01-17 21:46 ` Ivan Shcherbakov
0 siblings, 1 reply; 3+ messages in thread
From: Neil Jerram @ 2010-01-17 21:44 UTC (permalink / raw)
To: Ivan Shcherbakov; +Cc: bug-guile
Ivan Shcherbakov <shcherbakov@eit.uni-kl.de> writes:
> Hi, All,
>
> There is a bug in libguile/stackchk.h file. In some cases, when
> integer value of the stack pointer is less than stack checking limit,
> false positives are produced.
>
> The following code is responsible for the problem:
> # define SCM_STACK_OVERFLOW_P(s)\
> (SCM_STACK_PTR (s) \
> < (SCM_I_CURRENT_THREAD->base - SCM_STACK_LIMIT))
>
> When SCM_I_CURRENT_THREAD->base < SCM_STACK_LIMIT holds,
> the last part of the exception produces an overflow and the entire
> expression holds even when no stack overflow occurs.
>
> To fix the problem, the SCM_STACK_OVERFLOW() should be replaced by the
> following one:
>
> # define SCM_STACK_OVERFLOW_P(s)\
> ((SCM_I_CURRENT_THREAD->base - SCM_STACK_PTR (s)) \
> > SCM_STACK_LIMIT)
>
> This ensures that the difference between the stack base and the
> examined local variable address is always computed correctly
> regardless the integer value of the stack pointer.
That all makes sense, but are you seeing this problem in practice?
Thanks,
Neil
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: bug in stackchk.h
2010-01-17 21:44 ` Neil Jerram
@ 2010-01-17 21:46 ` Ivan Shcherbakov
0 siblings, 0 replies; 3+ messages in thread
From: Ivan Shcherbakov @ 2010-01-17 21:46 UTC (permalink / raw)
To: Neil Jerram; +Cc: bug-guile
Hi, Neil,
>That all makes sense, but are you seeing this problem in practice?
Yes, it caused false positives on a MSYS (Windows) build of guile.
--
Best regards,
Ivan Shcherbakov mailto:shcherbakov@eit.uni-kl.de
TU Kaiserslautern, Germany
Department of Real-Time Systems
^ permalink raw reply [flat|nested] 3+ messages in thread
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2010-01-06 21:37 bug in stackchk.h Ivan Shcherbakov
2010-01-17 21:44 ` Neil Jerram
2010-01-17 21:46 ` Ivan Shcherbakov
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