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1 | Copyright 2004 Linus Torvalds |
2 | Copyright 2004 Pavel Machek <pavel@suse.cz> | |
3 | ||
4 | Using sparse for typechecking | |
5 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
6 | ||
7 | "__bitwise" is a type attribute, so you have to do something like this: | |
8 | ||
9 | typedef int __bitwise pm_request_t; | |
10 | ||
11 | enum pm_request { | |
12 | PM_SUSPEND = (__force pm_request_t) 1, | |
13 | PM_RESUME = (__force pm_request_t) 2 | |
14 | }; | |
15 | ||
16 | which makes PM_SUSPEND and PM_RESUME "bitwise" integers (the "__force" is | |
17 | there because sparse will complain about casting to/from a bitwise type, | |
18 | but in this case we really _do_ want to force the conversion). And because | |
19 | the enum values are all the same type, now "enum pm_request" will be that | |
20 | type too. | |
21 | ||
22 | And with gcc, all the __bitwise/__force stuff goes away, and it all ends | |
23 | up looking just like integers to gcc. | |
24 | ||
25 | Quite frankly, you don't need the enum there. The above all really just | |
26 | boils down to one special "int __bitwise" type. | |
27 | ||
28 | So the simpler way is to just do | |
29 | ||
30 | typedef int __bitwise pm_request_t; | |
31 | ||
32 | #define PM_SUSPEND ((__force pm_request_t) 1) | |
33 | #define PM_RESUME ((__force pm_request_t) 2) | |
34 | ||
35 | and you now have all the infrastructure needed for strict typechecking. | |
36 | ||
37 | One small note: the constant integer "0" is special. You can use a | |
38 | constant zero as a bitwise integer type without sparse ever complaining. | |
39 | This is because "bitwise" (as the name implies) was designed for making | |
40 | sure that bitwise types don't get mixed up (little-endian vs big-endian | |
41 | vs cpu-endian vs whatever), and there the constant "0" really _is_ | |
42 | special. | |
43 | ||
55032eac | 44 | Use |
1da177e4 | 45 | |
55032eac | 46 | make C=[12] CF=-Wbitwise |
1da177e4 LT |
47 | |
48 | or you don't get any checking at all. | |
49 | ||
50 | ||
51 | Where to get sparse | |
52 | ~~~~~~~~~~~~~~~~~~~ | |
53 | ||
86513e72 | 54 | With git, you can just get it from |
1da177e4 | 55 | |
86513e72 | 56 | rsync://rsync.kernel.org/pub/scm/devel/sparse/sparse.git |
1da177e4 LT |
57 | |
58 | and DaveJ has tar-balls at | |
59 | ||
e272d506 | 60 | http://www.codemonkey.org.uk/projects/git-snapshots/sparse/ |
1da177e4 LT |
61 | |
62 | ||
63 | Once you have it, just do | |
64 | ||
65 | make | |
66 | make install | |
67 | ||
68 | as your regular user, and it will install sparse in your ~/bin directory. | |
69 | After that, doing a kernel make with "make C=1" will run sparse on all the | |
70 | C files that get recompiled, or with "make C=2" will run sparse on the | |
71 | files whether they need to be recompiled or not (ie the latter is fast way | |
72 | to check the whole tree if you have already built it). |