[R] memory allocation and interrupts
p.dalgaard at biostat.ku.dk
Sat Jun 12 10:47:17 CEST 2004
Prof Brian Ripley <ripley at stats.ox.ac.uk> writes:
> On Fri, 11 Jun 2004, Vadim Ogranovich wrote:
> > A recent discussion on the list about tryCatch and signals made me think
> > about memory allocation and signals in C extension modules. What happens
> > to the memory allocated by R_alloc and Calloc if the user pressed Ctr-C
> > during the call? R-ext doesn't seem to discuss this. I'd guess that
> > R_alloc is interrupt-safe while Calloc is not, but I am not sure. In any
> > case a paragraph in R-ext on signals would be helpful.
> Easy: such code is not interruptible by Ctrl-C (sic). And that *is* in
> R_exts.* (sic), even with an entry `interrupts' in its index!
The programmer might reenable interrupts though. This is not something
that we have a precedence (nor a policy) for, but it has crossed my
mind a couple of times.
In some cases it should be possible to wrap time-consuming C code in a
setjmp/longjmp construct. It's not possible to do it generally because
all hell breaks loose if the C code calls back into R, but not all C
code does that.
Of course it is critically important that the code resets the
interrupt handling to a sane state when it is done, so it would be
nice if we could abstract a reasonably safe construction into a
O__ ---- Peter Dalgaard Blegdamsvej 3
c/ /'_ --- Dept. of Biostatistics 2200 Cph. N
(*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk) FAX: (+45) 35327907
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