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Linus Torvalds1da177e2005-04-16 15:20:36 -07001Copyright 2004 Linus Torvalds
2Copyright 2004 Pavel Machek <pavel@suse.cz>
Bob Copelande8331952006-06-23 02:06:09 -07003Copyright 2006 Bob Copeland <me@bobcopeland.com>
Linus Torvalds1da177e2005-04-16 15:20:36 -07004
5Using 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
17which makes PM_SUSPEND and PM_RESUME "bitwise" integers (the "__force" is
18there because sparse will complain about casting to/from a bitwise type,
19but in this case we really _do_ want to force the conversion). And because
20the enum values are all the same type, now "enum pm_request" will be that
21type too.
22
23And with gcc, all the __bitwise/__force stuff goes away, and it all ends
24up looking just like integers to gcc.
25
26Quite frankly, you don't need the enum there. The above all really just
27boils down to one special "int __bitwise" type.
28
29So 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
36and you now have all the infrastructure needed for strict typechecking.
37
38One small note: the constant integer "0" is special. You can use a
39constant zero as a bitwise integer type without sparse ever complaining.
40This is because "bitwise" (as the name implies) was designed for making
41sure that bitwise types don't get mixed up (little-endian vs big-endian
42vs cpu-endian vs whatever), and there the constant "0" really _is_
43special.
44
Sam Ravnborg20375bf2009-04-10 13:18:08 +020045__bitwise__ - to be used for relatively compact stuff (gfp_t, etc.) that
46is mostly warning-free and is supposed to stay that way. Warnings will
47be generated without __CHECK_ENDIAN__.
48
49__bitwise - noisy stuff; in particular, __le*/__be* are that. We really
50don't want to drown in noise unless we'd explicitly asked for it.
51
52
Bob Copelande8331952006-06-23 02:06:09 -070053Getting sparse
54~~~~~~~~~~~~~~
Linus Torvalds1da177e2005-04-16 15:20:36 -070055
Dave Jonesa55028f2007-03-08 19:45:26 -050056You can get latest released versions from the Sparse homepage at
Bill Pemberton05be7a82010-04-27 16:20:15 -040057https://sparse.wiki.kernel.org/index.php/Main_Page
Linus Torvalds1da177e2005-04-16 15:20:36 -070058
Dave Jonesa55028f2007-03-08 19:45:26 -050059Alternatively, you can get snapshots of the latest development version
60of sparse using git to clone..
Linus Torvalds1da177e2005-04-16 15:20:36 -070061
Bill Pemberton05be7a82010-04-27 16:20:15 -040062 git://git.kernel.org/pub/scm/devel/sparse/sparse.git
Dave Jonesa55028f2007-03-08 19:45:26 -050063
64DaveJ has hourly generated tarballs of the git tree available at..
Linus Torvalds1da177e2005-04-16 15:20:36 -070065
Bob Copelande8331952006-06-23 02:06:09 -070066 http://www.codemonkey.org.uk/projects/git-snapshots/sparse/
Linus Torvalds1da177e2005-04-16 15:20:36 -070067
68
69Once you have it, just do
70
71 make
72 make install
73
Bob Copelande8331952006-06-23 02:06:09 -070074as a regular user, and it will install sparse in your ~/bin directory.
75
76Using sparse
77~~~~~~~~~~~~
78
79Do a kernel make with "make C=1" to run sparse on all the C files that get
80recompiled, or use "make C=2" to run sparse on the files whether they need to
81be recompiled or not. The latter is a fast way to check the whole tree if you
82have already built it.
83
Geert Uytterhoevena887a072008-06-20 15:45:12 +020084The optional make variable CF can be used to pass arguments to sparse. The
85build system passes -Wbitwise to sparse automatically. To perform endianness
86checks, you may define __CHECK_ENDIAN__:
Bob Copelande8331952006-06-23 02:06:09 -070087
Geert Uytterhoevena887a072008-06-20 15:45:12 +020088 make C=2 CF="-D__CHECK_ENDIAN__"
Bob Copelande8331952006-06-23 02:06:09 -070089
90These checks are disabled by default as they generate a host of warnings.