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fix undefined behavior in getdelim via null pointer arithmetic and memcpy

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both passing a null pointer to memcpy with length 0, and adding 0 to a
null pointer, are undefined. in some sense this is 'benign' UB, but
having it precludes use of tooling that strictly traps on UB. there
may be better ways to fix it, but conditioning the operations which
are intended to be no-ops in the k==0 case on k being nonzero is a
simple and safe solution.
This commit is contained in:
Rich Felker 2021-09-11 21:21:43 -04:00
parent b713b8b2e4
commit e3e7189c11
1 changed files with 5 additions and 3 deletions
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8
src/stdio/getdelim.c
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@ -55,9 +55,11 @@ ssize_t getdelim(char **restrict s, size_t *restrict n, int delim, FILE *restric
*s = tmp;
*n = m;
}
memcpy(*s+i, f->rpos, k);
f->rpos += k;
i += k;
if (k) {
memcpy(*s+i, f->rpos, k);
f->rpos += k;
i += k;
}
if (z) break;
if ((c = getc_unlocked(f)) == EOF) {
if (!i || !feof(f)) {