Contents of /alx-src/tags/kernel26-2.6.12-alx-r9/Documentation/sparse.txt
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Wed Mar 4 11:03:09 2009 UTC (15 years, 3 months ago) by niro
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Wed Mar 4 11:03:09 2009 UTC (15 years, 3 months ago) by niro
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Tag kernel26-2.6.12-alx-r9
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 | |
44 | Modify top-level Makefile to say |
45 | |
46 | CHECK = sparse -Wbitwise |
47 | |
48 | or you don't get any checking at all. |
49 | |
50 | |
51 | Where to get sparse |
52 | ~~~~~~~~~~~~~~~~~~~ |
53 | |
54 | With BK, you can just get it from |
55 | |
56 | bk://sparse.bkbits.net/sparse |
57 | |
58 | and DaveJ has tar-balls at |
59 | |
60 | http://www.codemonkey.org.uk/projects/bitkeeper/sparse/ |
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). |