Full_Name: Vilmos Prokaj
Version: R 2.7.1
OS: windows
Submission from: (NULL) (213.181.195.84)
Dear developers,
The following line of code (produced by a mistake) caused an infinite loop
unique("a",c("a","b"))
or also
unique(1,1:2)
I made a little investigation, and it seems to be that the following function
from unique.c is looping infinitely
static int isDuplicated(SEXP x, int indx, HashData *d)
{
int i, *h;
h = INTEGER(d->HashTable);
i = d->hash(x, indx, d);
while (h[i] != NIL) {
if (d->equal(x, h[i], x, indx))
return h[i] >= 0 ? 1 : 0;
i = (i + 1) % d->M;
}
h[i] = indx;
return 0;
}
In this case h contains only one negative value, which causes d->equal(=requal)
to return 0.
static int requal(SEXP x, int i, SEXP y, int j)
{
if (i < 0 || j < 0) return 0;
if (!ISNAN(REAL(x)[i]) && !ISNAN(REAL(y)[j]))
return (REAL(x)[i] == REAL(y)[j]);
else if (R_IsNA(REAL(x)[i]) && R_IsNA(REAL(y)[j])) return 1;
else if (R_IsNaN(REAL(x)[i]) && R_IsNaN(REAL(y)[j])) return 1;
else return 0;
}
I do not claim that the situation above is frequent or even meaningful, however
it should not cause a crash of R.
Sincerely yours
Vilmos Prokaj
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