docs: sphinxify sparse.txt and move to dev-tools

Copyright 2004 Linus Torvalds

Copyright 2004 Pavel Machek <pavel@ucw.cz>

Copyright 2006 Bob Copeland <me@bobcopeland.com>

.. Copyright 2004 Linus Torvalds

.. Copyright 2004 Pavel Machek <pavel@ucw.cz>

.. Copyright 2006 Bob Copeland <me@bobcopeland.com>

Sparse

======

Sparse is a semantic checker for C programs; it can be used to find a

number of potential problems with kernel code.  See

https://lwn.net/Articles/689907/ for an overview of sparse; this document

contains some kernel-specific sparse information.

Using sparse for typechecking

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

-----------------------------

"__bitwise" is a type attribute, so you have to do something like this:

"__bitwise" is a type attribute, so you have to do something like this::

        typedef int __bitwise pm_request_t;

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.

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

So the simpler way is to just do::

        typedef int __bitwise pm_request_t;

don't want to drown in noise unless we'd explicitly asked for it.

Using sparse for lock checking

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

------------------------------

The following macros are undefined for gcc and defined during a sparse

run to use the "context" tracking feature of sparse, applied to

sparse would otherwise report a context imbalance.

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..

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..

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

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

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__:

checks, you may define __CHECK_ENDIAN__::

        make C=2 CF="-D__CHECK_ENDIAN__"

   :maxdepth: 2

   coccinelle

   sparse