Linus On Coding Style
1 Oct - 7 Oct (26 posts) Subject: "[patch] Workqueue Abstraction, 2.5.40-H7"
In the course of discussing a workqueue abstraction patch, Linus Torvalds gave
some opinions of coding style issues:
Pease don't introduce more typedefs. They only hide what the hell the thing
is, which is actively _bad_ for structures, since passing a structure by
value etc is something that should never be done, for example.
The few saved characters of typing do not actually _buy_ you anything else,
and only obscures what the thing is.
Also, it's against the Linux coding standard, which does not like adding
magic single-letter suffixes to things - that also is the case for your
strange "_s" suffix for a structure (the real suffix is "_struct").
Remember: typing out something is not bad. It's _especially_ not bad if the
typing makes it more clear what the thing is.
He added in reply to himself:
Btw, just to avoid counter-examples: Linux does use structures and typedefs
occasionally to hide and force compiler typechecking on small structures on
purpose. We have a few places where we do things like
typedef struct {
unsigned int value;
} atomic_t;
(and similar things for the page table entries etc).
This is done because the things are often really regular scalars, but we
use the structure as a strict type checking mechanism. In this case, using
a typedef is fine, because we don't actually ever want to _access_ it as a
structure, and the typedef provices exactly the kind of information hiding
that we need.
But type hiding for a real structure just doesn't make sense, since we use
it as a true structure, and hiding information just makes it harder to see.
Elsewhere, he added:
Big things should have big names. That's why "u8" is u8, because it's not
just physically small, it also has very little semantics associated with
it.
I want those variable declarations to stand out, and make people understand
that this is not just a variable, it's a structure, and it may be taking up
a noticeable amount of space on the stack, for example.
That's the main issue for me. I don't personally care so much about trying
to avoid dependencies in the header files that can also be problematic.
That's probably partly because I use fast enough machines that parsing them
a few extra times doesn't much bother me, and circular requirements tend to
be rare enough not to bother me unduly.
So the thing is a big red warning sign that you're now using a complex data
structure, and you should be aware of the semantics that go with it.
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software quality
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10/14/2002 2:33 PM
jcohen
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