Manual Reference Pages - PYCOCCI (1)
pycocci - Coccinelle wrapper for SmPL patch development
[-h | --help]
[-p | --profile-cocci]
[-j | --jobs <job-digit> ]
[-v | --verbose]
[-s | --show-proof]
Multithread Argument Heuristics
Indexing Argument Heuristics
pycocci is wrapper around spatch, it enables a set of default
arguments and also uses a bit of heuristics to infers which arguments you
likely want enabled. It takes two arguments, the <SmPL-patch.cocci> and your
<target> which can either be a directory or file. The actual command run
is always displayed on standard output.
Coccinelle spatch is a very rich tool, it provides a large set of
features for use with the Coccinelle engine. Typical day to day SmPL patch
development may only require a base set of features though, we can also infer
a set of features depending on your target. pycocci enables a set of
flags which over time have been determined to be required for day to day
Linux kernel development, for instance through a cronjob, it also uses a set
of heuristics to infer a set of arguments to use depending on your release of
Coccinelle. pycocci also checks to see which version of Coccinelle you
have installed and looks to enable arguments depending on what version of
Coccinelle you have installed.
pycocci can also be used to help write and verify SmPL patches when
replacing a regular patch series. pycocci checks the version of
spatch installed and based on this enables a set of features. This man
page will document what options it always enables by default, why it has
done this and it will also document the heuristics used and logic behind them.
By default pycocci will always enable when running spatch:
The --in-place option is enabled by default as most development these
days happens on version control systems and built-in version control systems
can typically display differences better.
--relax-include-path and --relax-include-path are enabled by
default given that at least for Linux kernel development some C files tend to
include headers in paths only specified by a targets Makefile through
utilities such as subdir-ccflags or ccflags-y making it difficult to ensure
all required header files are read by Coccinelle. We are agressive with
headers search and inclusion.
A default timeout of 120 seconds is used by default. Not using a timeout
is typically not a good idea. The value of 120 is used by default and is
considered significantly large enough to support most SmPL patches.
We make use of --dir to enable use of a target directory and its
MULTITHREAD ARGUMENT HEURISTICS
Coccinelle spatch prior to release 1.0.0 provided support for
multithreading but required the developer to spawn each thread on
their own, and provide an index reference number identifying each
thread. Coccinelle would divide the amount of work required to be
done and based on the index grant the thread a specific set of work.
Some shell scripts could be used to help split the work out for you.
pycocci was originally written to supercede these scripts and
use Pythons multithreaded support, while also enabling some sensible
arguments by default.
If you have a version of spatch older than 1.0.2 pycocci will
provide its own built-in multithreaded batched solution, the spatch
--jobs argument is enabled on spatch >= 1.0.2. The spatch --jobs
arguments takes advantage of Coccinelles built-in paramap support, and
performance-wise yields better results than pycoccis multithreaded
solution. The number of threads used will always default to the number of
number of CPUs on your system, this is taken from what Python
multiprocessing.cpu_count() returns. You can override the number of threads
pycocci will use with the --jobs argument.
INDEXING ARGUMENT HEURISTICS
Coccinelle pycocci supports using a series of indexing alternatives:
Coccinelle puts the onus of which indexing feature to enable on the developer.
pycocci will figure things out for you and make sure that only supported
options are used in specific supported releases of coccinelle. So for instance,
although --use-gitgrep has been available on 1.0.1 pycocci will only
it on 1.0.2. The order of preference for what indexing option to uses the
following heuristics: If your target directory has a .glimpse_index file we
assume you will want to use --use-glimpse. Glimpse is now released under the
ISC license and performance-wise is known to work as the best indexing
alternative, this is why we always check for a glimpse index first. This
heuristic is however limited, you need the target path to be the base
directory where the .glimpse_index file exists, otherwise pycocci
will not recurse below on sub-directories. If we determine glimpse cannot
be used then pycocci will use git rev-parse --toplevel on the specified
path to determine if the provided path is part of a git directory to enable
--use-gitgrep. Although coccinelle provides a fail-safe mechanism to enable
use of --use-gitgrep and fall back onto --use-coccigrep if a git tree is
not used, we avoid the failure case ahead of time. pycocci will be
tuned through each release to infer the best indexing option known to
use on your target path.
Further information about spatch is available at
Here is a summary of the options available on pycocci:
[-h | --help]
[-p | --profile-cocci]
[-j | --jobs]
[-v | --verbose]
[-s | --show-proof]
-h | --help |
print short help menu
Profile the <SmPL patch> when run against <target>
Override the default number of jobs to use with <job-digit>. You really
only need this if the heuristics for the default number of jobs is
determined to be incorrect.
Output all possible information when run. By default pycocci will
provide no output unless an error is found.
Show that the <SmPL-patch.cocci> can replace a series of patches. The <SmPL-patch.cocci>
must have a .cocci postfix. A series of patches are expected to exist in the
directory named after the <SmPL-patch.cocci> with the .cocci postfix removed.
pycocci will use git in order to show a proof of equivalence between the
two. A new git branch will be created and used to apply the series of patches
("pycocci-patch-8-random-chars") onto the <target>, another git branch will be created and
used to apply the <SmPL-patch.cocci> ("pycocci-smpl-8-random-chars"). pycocci will
display name of the newly created branches and finally provide the
output of git diff --stat <pycocci-patch-8-random-chars>..<pycocci-smpl-8-random-chars>. You should see
no changes, and therefore a perfect SmPL patch equivalence, when the diffstat
on the ouput shows no changes. The way to interpet a positive diffstat is that
the <SmPL-patch.cocci> is introducing more changes than the patch series. The
way to interpret a negative diffstat is that the <SmPL-patch.cocci> is lacking
some changes in place on the patch series. pycocci will use git rev-parse --toplevel
against the <target> to see if the <target> is part of a git tree. If the <target>
is not part of a git tree a git tree is created for you on <target> if <target>
is a directory or on the base directory of <target> if <target> is a file.
pycocci will return you to the branch previously set on the <target> if
one was previously set, otherwise if a new git tree was created for you pycocci
will set the tree back to the master branch. Each run of pycocci --show-proof
will create two new git branches. 8 random characters are postixed to each new
git branch created to avoid conflicts with previous runs.
pycocci and this man page was written by Luis R. Rodriguez <firstname.lastname@example.org>
Send an mail to <email@example.com>
Copyright 2015, Luis R. Rodriguez
pycocci is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, according to version 2 of the License.
spatch(1), pycocci(1), diff(1)
|--> ||PYCOCCI (1) ||July 20, 2015 |
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