On 06/10/2010 10:53 AM, David wrote:
Hello,
I used to use a (somehow complicated) code in C and I have tried to adapt it
to be called from R without making an excessive amount of changes. I am
afraid I cannot post the code here, but I am going to try to describe the
problem as accurately as possible.
I have some arguments that are most of the cases required for internal C
operations only; but as they are needed a few times as arguments, they are
still passed as arguments. Another argument is a "switch" (with value 0 or
1) that states whether these "arguments" are really needed as arguments or
not. When such switch is 0 (says "no"), the C code "feels free" to
manipulate these "arguments", and in particular it tries to modify its
extension (reallocate).
You should be using .Call rather than .C if you need to modify
allocations. You should treat arrays passed via .C as fixed size.
If you want to stick with the .C convention, then I think you'll need
two calls: one to return the required sizes, and a second one with new
vectors allocated at those sizes. It's often easier to learn how .Call
works.
Duncan Murdoch
To be clear:
I define the "argument" in R: values1<- double(size)
values1 is passed as an argument in ".C".
If the switch is set to 0 (says that "values1" is not a real argument), the
C function tries to reallocate the pseudo-argument values1:
double *tmp2 = realloc(values1, new_size);
if(tmp2 != NULL){
values1 = tmp2;
}
else{
Rprintf("\nFATAL ERROR: Could not allocate memory for the
array\n");
exit(2);
}
But then, when calling the function ".C", I get *** error for object ...:
pointer being reallocated was not allocated
Is there any workaround for this?
Thank you very much in advance,
David
Can you please Cc to me any replies, just in case I may miss any of them
among the whole amount of emails :-) ?
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