Christian Couder <christian.couder@xxxxxxxxx> writes:
> If it's -1 instead of 0, then it might be a bit more complex to
> initialize structs that contain such a field, as it cannot be done
> with only xcalloc().
In general, yes, but I would have thought that the codepath that
allocates used_atom[] elements are pretty isolated---it is not like
there are random xcalloc() all over the code. In fact, there is
only one "used_atom_cnt++" in the whole file, which means there is
only one place that (re)allocates the array.
...
at = used_atom_cnt;
used_atom_cnt++;
REALLOC_ARRAY(used_atom, used_atom_cnt);
used_atom[at].name = xmemdupz(atom, ep - atom);
used_atom[at].type = valid_atom[i].cmp_type;
used_atom[at].source = valid_atom[i].source;
...
So, I do not think there is even any need to worry about "initialize
to invalid and fill it in as we discover what it really is"; if
there were such a use pattern, UNKNOWN would be handy, but that is
not what we are dealing with here. In the above snippet, we already
have found from which valid_atom[] element to instantiate the new
element in used_atom[] array.
>> > + * ATOM_INVALID equals to the size of valid_atom array, which could help us
>> > + * iterate over valid_atom array like this:
>> > + *
>> > + * for (i = ATOM_UNKNOWN + 1; i < ATOM_INVALID; i++) {
>>
>> I find it far more intuitive to say
>>
>> for (i = 0; i < ATOM_INVALID; i++)
>>
>> than having to say UNKNOWN+1.
And here I was being embarrassingly silly.
As long as we do not waste any entry in valid_atom[] with leading
gap, trailing gap or gap in the middle, the way to iterate over such
an array is
for (i = 0; i < ARRAY_SIZE(valid_atom); i++)
hence, there is no need for ATOM_MAX, and no need to burden us to
remember that UNKNOWN is near the bottom of the range, and INVALID
is near the top of the range.
