On Tue, 12 Jun 2012, Pawel Jakub Dawidek wrote:
On Tue, Jun 12, 2012 at 12:53:47PM +1000, Bruce Evans wrote:
On Mon, 11 Jun 2012, Pawel Jakub Dawidek wrote:
- KASSERT(fd >= 0 && fd < fdp->fd_nfiles,
+ KASSERT((unsigned int)fd < fdp->fd_nfiles,
("file descriptor %d out of range (0, %d)", fd, fdp->fd_nfiles));
return ((fdp->fd_map[NDSLOT(fd)] & NDBIT(fd)) != 0);
}
This is backwards. Apart from using the worst possible (most verbose)
spelling of `unsigned', it uses a type hack manually optimize away the
test for fd being < 0. The compiler will do this "optimization"
automatically if it is any good (or undo it if it is not), so all the
hack does is obfuscate the test. With the verbose spelling of u_int,
it even takes more space.
Well, to be honest I presonally would prefer explicit check for fd being
less than 0, but my impression was that using cast is the most popular
way and I wanted this check to be consistent across our source tree.
Feel free to change it.
I'm only free to ask you to back out it out.
BTW. I really dislike using 'unsigned' with omitted 'int'. u_int is fine.
I really dislike 'unsigned int'. The int in it is just noise, as in
'long int'.
From K&R 1: p34: "The declarations for the qualifiers look like [...]
unsigned int x; The word int can be omitted in such situations, and
typically is." p45: example that uses plain unsigned. p183: "Unisgned
integers, declared unsigned, ...". p193: [semi-formal grammar]:
"type-specifier: char, short, int, long, unsigned, float, double,
struct-or-union-specifier, typedef-name. [short int, long int,
unsigned int, long float are also acceptable]".
From K&R 2: p36: same as above p34. p49: similar to above p45 (now
missing in index; no longer "implicit int" for the function return
type; excessive use of unsigned fixed). p196: similar to above p183
(now says "...declared using the unsigned keyword). p211: similzr to
above p193 (add void, signed, enum-specifier; remove long float, and
tighten up the description of which combinations are allowed in other
ways).
Other interesting points from K&R:
- according to the grammar, both `unsigned' and 'signed' are full-fledged
types, not qualifiers for integer types. You can even write plain
'signed' meaning 'signed int', but no one does that.
- K&R very rarely uses `unsigned'. This shows that it should rarely be
used. I could only find the above examples in it (these are all that
are in the index for K&R 1), plus 1 more a page later than the p45/49
one (the index is broken in a different way for this -- in K&R 1 the
one on p46 is not indexed, while in K&R 2 the one on p49 is not
indexed).
Bruce
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