From 849369d6c66d3054688672f97d31fceb8e8230fb Mon Sep 17 00:00:00 2001 From: root Date: Fri, 25 Dec 2015 04:40:36 +0000 Subject: initial_commit --- Documentation/sparse.txt | 90 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 90 insertions(+) create mode 100644 Documentation/sparse.txt (limited to 'Documentation/sparse.txt') diff --git a/Documentation/sparse.txt b/Documentation/sparse.txt new file mode 100644 index 00000000..4909d411 --- /dev/null +++ b/Documentation/sparse.txt @@ -0,0 +1,90 @@ +Copyright 2004 Linus Torvalds +Copyright 2004 Pavel Machek +Copyright 2006 Bob Copeland + +Using sparse for typechecking +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +"__bitwise" is a type attribute, so you have to do something like this: + + typedef int __bitwise pm_request_t; + + enum pm_request { + PM_SUSPEND = (__force pm_request_t) 1, + PM_RESUME = (__force pm_request_t) 2 + }; + +which makes PM_SUSPEND and PM_RESUME "bitwise" integers (the "__force" is +there because sparse will complain about casting to/from a bitwise type, +but in this case we really _do_ want to force the conversion). And because +the enum values are all the same type, now "enum pm_request" will be that +type too. + +And with gcc, all the __bitwise/__force stuff goes away, and it all ends +up looking just like integers to gcc. + +Quite frankly, you don't need the enum there. The above all really just +boils down to one special "int __bitwise" type. + +So the simpler way is to just do + + typedef int __bitwise pm_request_t; + + #define PM_SUSPEND ((__force pm_request_t) 1) + #define PM_RESUME ((__force pm_request_t) 2) + +and you now have all the infrastructure needed for strict typechecking. + +One small note: the constant integer "0" is special. You can use a +constant zero as a bitwise integer type without sparse ever complaining. +This is because "bitwise" (as the name implies) was designed for making +sure that bitwise types don't get mixed up (little-endian vs big-endian +vs cpu-endian vs whatever), and there the constant "0" really _is_ +special. + +__bitwise__ - to be used for relatively compact stuff (gfp_t, etc.) that +is mostly warning-free and is supposed to stay that way. Warnings will +be generated without __CHECK_ENDIAN__. + +__bitwise - noisy stuff; in particular, __le*/__be* are that. We really +don't want to drown in noise unless we'd explicitly asked for it. + + +Getting sparse +~~~~~~~~~~~~~~ + +You can get latest released versions from the Sparse homepage at +https://sparse.wiki.kernel.org/index.php/Main_Page + +Alternatively, you can get snapshots of the latest development version +of sparse using git to clone.. + + git://git.kernel.org/pub/scm/devel/sparse/sparse.git + +DaveJ has hourly generated tarballs of the git tree available at.. + + http://www.codemonkey.org.uk/projects/git-snapshots/sparse/ + + +Once you have it, just do + + make + make install + +as a regular user, and it will install sparse in your ~/bin directory. + +Using sparse +~~~~~~~~~~~~ + +Do a kernel make with "make C=1" to run sparse on all the C files that get +recompiled, or use "make C=2" to run sparse on the files whether they need to +be recompiled or not. The latter is a fast way to check the whole tree if you +have already built it. + +The optional make variable CF can be used to pass arguments to sparse. The +build system passes -Wbitwise to sparse automatically. To perform endianness +checks, you may define __CHECK_ENDIAN__: + + make C=2 CF="-D__CHECK_ENDIAN__" + +These checks are disabled by default as they generate a host of warnings. -- cgit v1.2.3