On Thu, 21 Sep 2023 09:46:26 +0200
Jan Gorecki <j.gore...@wit.edu.pl> wrote:
> I would like to safely allocate R object from C. By safely I mean
> that, I can test if allocation succeeded or failed, and then raise
> exception myself.
> R_alloc and allocVector both raises exception straightaway, so I am
> not able to handle failed allocation myself.
All R objects are subject to garbage collection (as potential garbage
or at least as a source of information about live objects), so they
have to be allocated by talking to the GC. (This also means that
R_alloc() is not a good way to create new SEXPs.)
It's not that it's impossible to return a failure code on allocation
failures instead of performing a longjmp() away from your code, but
since the rest of error handling in R works this way, extension code
has to always be ready to be longjmp()'d away from at every R API call.
How about catching the exception instead?
struct alloc_args { SEXPTYPE type; R_xlen_t len; };
static SEXP do_allocate(void * arguments) {
struct alloc_args * args = arguments;
return allocVector(args->type, args->len);
}
static SEXP maybe_allocate(SEXPTYPE type, R_xlen_t len) {
struct alloc_args args = { .type = type, .len = len };
return R_tryCatchError(do_allocate, &args, NULL, NULL);
} // returns R_NilValue on failure via the default tryCatch handler
Code is untested but should work according to WRE:
https://cran.r-project.org/doc/manuals/R-exts.html#Condition-handling-and-cleanup-code
--
Best regards,
Ivan
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