Messages in this thread | | | Date | Tue, 23 Jun 2015 12:51:45 +0200 (CEST) | From | Julia Lawall <> | Subject | Re: [PATCH 01/12] staging: lustre: fid: Use !x to check for kzalloc failure |
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On Tue, 23 Jun 2015, Dan Carpenter wrote:
> Yes. I know Al's thoughts and kernel style. > > But Alan Cox and Andreas have both said they think (x == NULL) can help > you avoid some kind of boolean vs pointer bugs. I've had co-workers who > did massive seds changing !foo to foo == NULL on our code base. But > I've never seen a real life example of a bug this fixes. > > To be honest, I've never seen a real life proof that (!foo) code is less > buggy. I should look through the kbuild mailbox... Hm... But my other > idea of setting up code style readability testing website is also a good > one. > > Linux kernel style is based on Joe Perches finding that 80% of the code > prefers one way or the other. That's a valid method for determining > code style. I bet it normally picks the more readable style but it > would be interesting to measure it more formally.
On today's linux-next, I find 3218 tests on the result of kmalloc etc using NULL and 14429 without, making 82% without. The complete semantic patch is shown below.
julia
@initialize:ocaml@ @@
let withnull = ref 0 let withoutnull = ref 0
@r1 disable is_null, isnt_null1 exists@ expression x,e; position p; statement S1,S2; @@
x = \(kmalloc\|kzalloc\|kcalloc\|devm_kmalloc\|devm_kzalloc\)(...) ... when != x = e when != &x if@p (<+...\(x == NULL\|x != NULL\|NULL == x\|NULL != x\)...+>) S1 else S2
@r2 disable not_ptr1, not_ptr2 exists@ expression x,e; position p; statement S1,S2; @@
x = \(kmalloc\|kzalloc\|kcalloc\|devm_kmalloc\|devm_kzalloc\)(...) ... when != x = e when != &x if@p (<+...\(!x\|x && ...\|x || ...\)...+>) S1 else S2
@script:ocaml@ _p << r1.p; @@ withnull := !withnull + 1
@script:ocaml@ _p << r2.p; @@ withoutnull := !withoutnull + 1
@finalize:ocaml@ @@
Printf.printf "withnull %d withoutnull %d\n" !withnull !withoutnull
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