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waleedq authored
1 Copyright 2004 Linus Torvalds
2 Copyright 2004 Pavel Machek <pavel@suse.cz>
3 Copyright 2006 Bob Copeland <me@bobcopeland.com>
4
5 Using sparse for typechecking
6 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
7
8 "__bitwise" is a type attribute, so you have to do something like this:
9
10 typedef int __bitwise pm_request_t;
11
12 enum pm_request {
13 PM_SUSPEND = (__force pm_request_t) 1,
14 PM_RESUME = (__force pm_request_t) 2
15 };
16
17 which makes PM_SUSPEND and PM_RESUME "bitwise" integers (the "__force" is
18 there because sparse will complain about casting to/from a bitwise type,
19 but in this case we really _do_ want to force the conversion). And because
20 the enum values are all the same type, now "enum pm_request" will be that
21 type too.
22
23 And with gcc, all the __bitwise/__force stuff goes away, and it all ends
24 up looking just like integers to gcc.
25
26 Quite frankly, you don't need the enum there. The above all really just
27 boils down to one special "int __bitwise" type.
28
29 So the simpler way is to just do
30
31 typedef int __bitwise pm_request_t;
32
33 #define PM_SUSPEND ((__force pm_request_t) 1)
34 #define PM_RESUME ((__force pm_request_t) 2)
35
36 and you now have all the infrastructure needed for strict typechecking.
37
38 One small note: the constant integer "0" is special. You can use a
39 constant zero as a bitwise integer type without sparse ever complaining.
40 This is because "bitwise" (as the name implies) was designed for making
41 sure that bitwise types don't get mixed up (little-endian vs big-endian
42 vs cpu-endian vs whatever), and there the constant "0" really _is_
43 special.
44
45 __bitwise__ - to be used for relatively compact stuff (gfp_t, etc.) that
46 is mostly warning-free and is supposed to stay that way. Warnings will
47 be generated without __CHECK_ENDIAN__.
48
49 __bitwise - noisy stuff; in particular, __le*/__be* are that. We really
50 don't want to drown in noise unless we'd explicitly asked for it.
51
52
53 Getting sparse
54 ~~~~~~~~~~~~~~
55
56 You can get latest released versions from the Sparse homepage at
57 https://sparse.wiki.kernel.org/index.php/Main_Page
58
59 Alternatively, you can get snapshots of the latest development version
60 of sparse using git to clone..
61
62 git://git.kernel.org/pub/scm/devel/sparse/sparse.git
63
64 DaveJ has hourly generated tarballs of the git tree available at..
65
66 http://www.codemonkey.org.uk/projects/git-snapshots/sparse/
67
68
69 Once you have it, just do
70
71 make
72 make install
73
74 as a regular user, and it will install sparse in your ~/bin directory.
75
76 Using sparse
77 ~~~~~~~~~~~~
78
79 Do a kernel make with "make C=1" to run sparse on all the C files that get
80 recompiled, or use "make C=2" to run sparse on the files whether they need to
81 be recompiled or not. The latter is a fast way to check the whole tree if you
82 have already built it.
83
84 The optional make variable CF can be used to pass arguments to sparse. The
85 build system passes -Wbitwise to sparse automatically. To perform endianness
86 checks, you may define __CHECK_ENDIAN__:
87
88 make C=2 CF="-D__CHECK_ENDIAN__"
89
90 These checks are disabled by default as they generate a host of warnings.
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