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Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
73 lines
2.2 KiB
Plaintext
73 lines
2.2 KiB
Plaintext
Copyright 2004 Linus Torvalds
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Copyright 2004 Pavel Machek <pavel@suse.cz>
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Using sparse for typechecking
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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"__bitwise" is a type attribute, so you have to do something like this:
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typedef int __bitwise pm_request_t;
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enum pm_request {
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PM_SUSPEND = (__force pm_request_t) 1,
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PM_RESUME = (__force pm_request_t) 2
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};
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which makes PM_SUSPEND and PM_RESUME "bitwise" integers (the "__force" is
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there because sparse will complain about casting to/from a bitwise type,
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but in this case we really _do_ want to force the conversion). And because
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the enum values are all the same type, now "enum pm_request" will be that
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type too.
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And with gcc, all the __bitwise/__force stuff goes away, and it all ends
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up looking just like integers to gcc.
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Quite frankly, you don't need the enum there. The above all really just
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boils down to one special "int __bitwise" type.
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So the simpler way is to just do
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typedef int __bitwise pm_request_t;
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#define PM_SUSPEND ((__force pm_request_t) 1)
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#define PM_RESUME ((__force pm_request_t) 2)
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and you now have all the infrastructure needed for strict typechecking.
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One small note: the constant integer "0" is special. You can use a
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constant zero as a bitwise integer type without sparse ever complaining.
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This is because "bitwise" (as the name implies) was designed for making
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sure that bitwise types don't get mixed up (little-endian vs big-endian
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vs cpu-endian vs whatever), and there the constant "0" really _is_
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special.
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Use
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make C=[12] CF=-Wbitwise
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or you don't get any checking at all.
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Where to get sparse
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~~~~~~~~~~~~~~~~~~~
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With git, you can just get it from
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rsync://rsync.kernel.org/pub/scm/devel/sparse/sparse.git
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and DaveJ has tar-balls at
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http://www.codemonkey.org.uk/projects/git-snapshots/sparse/
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Once you have it, just do
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make
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make install
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as your regular user, and it will install sparse in your ~/bin directory.
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After that, doing a kernel make with "make C=1" will run sparse on all the
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C files that get recompiled, or with "make C=2" will run sparse on the
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files whether they need to be recompiled or not (ie the latter is fast way
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to check the whole tree if you have already built it).
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