blob: f9c99c9a54f937616903a5fa5d0b8fee2fd020ae [file] [log] [blame]
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
Bob Copelande8331952006-06-23 02:06:09 -070045Getting sparse
46~~~~~~~~~~~~~~
Linus Torvalds1da177e2005-04-16 15:20:36 -070047
Harald Welte86513e72005-09-23 13:24:10 -070048With git, you can just get it from
Linus Torvalds1da177e2005-04-16 15:20:36 -070049
Harald Welte86513e72005-09-23 13:24:10 -070050 rsync://rsync.kernel.org/pub/scm/devel/sparse/sparse.git
Linus Torvalds1da177e2005-04-16 15:20:36 -070051
52and DaveJ has tar-balls at
53
Bob Copelande8331952006-06-23 02:06:09 -070054 http://www.codemonkey.org.uk/projects/git-snapshots/sparse/
Linus Torvalds1da177e2005-04-16 15:20:36 -070055
56
57Once you have it, just do
58
59 make
60 make install
61
Bob Copelande8331952006-06-23 02:06:09 -070062as a regular user, and it will install sparse in your ~/bin directory.
63
64Using sparse
65~~~~~~~~~~~~
66
67Do a kernel make with "make C=1" to run sparse on all the C files that get
68recompiled, or use "make C=2" to run sparse on the files whether they need to
69be recompiled or not. The latter is a fast way to check the whole tree if you
70have already built it.
71
Robert P. J. Day1c7bafe2006-09-13 07:57:50 -040072The optional make variable CHECKFLAGS can be used to pass arguments to sparse.
73The build system passes -Wbitwise to sparse automatically. To perform
74endianness checks, you may define __CHECK_ENDIAN__:
Bob Copelande8331952006-06-23 02:06:09 -070075
Robert P. J. Day1c7bafe2006-09-13 07:57:50 -040076 make C=2 CHECKFLAGS="-D__CHECK_ENDIAN__"
Bob Copelande8331952006-06-23 02:06:09 -070077
78These checks are disabled by default as they generate a host of warnings.