sparse.txt 2.8 KB

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  1. Copyright 2004 Linus Torvalds
  2. Copyright 2004 Pavel Machek <pavel@suse.cz>
  3. Copyright 2006 Bob Copeland <me@bobcopeland.com>
  4. Using sparse for typechecking
  5. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  6. "__bitwise" is a type attribute, so you have to do something like this:
  7. typedef int __bitwise pm_request_t;
  8. enum pm_request {
  9. PM_SUSPEND = (__force pm_request_t) 1,
  10. PM_RESUME = (__force pm_request_t) 2
  11. };
  12. which makes PM_SUSPEND and PM_RESUME "bitwise" integers (the "__force" is
  13. there because sparse will complain about casting to/from a bitwise type,
  14. but in this case we really _do_ want to force the conversion). And because
  15. the enum values are all the same type, now "enum pm_request" will be that
  16. type too.
  17. And with gcc, all the __bitwise/__force stuff goes away, and it all ends
  18. up looking just like integers to gcc.
  19. Quite frankly, you don't need the enum there. The above all really just
  20. boils down to one special "int __bitwise" type.
  21. So the simpler way is to just do
  22. typedef int __bitwise pm_request_t;
  23. #define PM_SUSPEND ((__force pm_request_t) 1)
  24. #define PM_RESUME ((__force pm_request_t) 2)
  25. and you now have all the infrastructure needed for strict typechecking.
  26. One small note: the constant integer "0" is special. You can use a
  27. constant zero as a bitwise integer type without sparse ever complaining.
  28. This is because "bitwise" (as the name implies) was designed for making
  29. sure that bitwise types don't get mixed up (little-endian vs big-endian
  30. vs cpu-endian vs whatever), and there the constant "0" really _is_
  31. special.
  32. Getting sparse
  33. ~~~~~~~~~~~~~~
  34. You can get latest released versions from the Sparse homepage at
  35. http://www.kernel.org/pub/linux/kernel/people/josh/sparse/
  36. Alternatively, you can get snapshots of the latest development version
  37. of sparse using git to clone..
  38. git://git.kernel.org/pub/scm/linux/kernel/git/josh/sparse.git
  39. DaveJ has hourly generated tarballs of the git tree available at..
  40. http://www.codemonkey.org.uk/projects/git-snapshots/sparse/
  41. Once you have it, just do
  42. make
  43. make install
  44. as a regular user, and it will install sparse in your ~/bin directory.
  45. Using sparse
  46. ~~~~~~~~~~~~
  47. Do a kernel make with "make C=1" to run sparse on all the C files that get
  48. recompiled, or use "make C=2" to run sparse on the files whether they need to
  49. be recompiled or not. The latter is a fast way to check the whole tree if you
  50. have already built it.
  51. The optional make variable CHECKFLAGS can be used to pass arguments to sparse.
  52. The build system passes -Wbitwise to sparse automatically. To perform
  53. endianness checks, you may define __CHECK_ENDIAN__:
  54. make C=2 CHECKFLAGS="-D__CHECK_ENDIAN__"
  55. These checks are disabled by default as they generate a host of warnings.