			   LCLint Version 2.3
		       MIT/LCS Distribution Site
			    3 September 1997

			      David Evans
			 evs@larch.lcs.mit.edu

LCLint is a tool for statically checking C programs.  With minimal
effort, LCLint can be used as a better lint.  If additional effort is
invested adding annotations to programs, LCLint can perform stronger
checks than can be done by any standard lint.

LCLint does many of the traditional lint checks including unused
declarations, type inconsistencies, use-before-definition, unreachable
code, ignored return values, execution paths with no return, likely
infinite loops, and fall-through cases.  Our main focus, however, is on
more powerful checks that are made possible by additional information
given in source code annotations.  Annotations are stylized comments
that document certain assumptions about functions, variables,
parameters, and types.  They may be used to indicate where the
representation of a user-defined type is hidden, to limit where a global
variable may be used or modified, to constrain what a function
implementation may do to its parameters, and to express checked
assumptions about variables, types, structure fields, function
parameters, and function results.  In addition to the checks
specifically enabled by annotations, many of the traditional lint checks
are improved by exploiting this additional information.

Some problems detected by LCLint include:

o Violations of information hiding.  A user-defined type can be declared
  as abstract, and a message is reported where code inappropriately
  depends on the representation of the type.

o Inconsistent modification of caller-visible state.  Functions can be
  annotated with information on what caller-visible state may be modified
  by the function, and an error is reported if the modifications produces
  by the function contradict its declaration.  

o Inconsistent use of global variables.  Information on what global and
  file scope variables a function may use can be added to function
  declarations, and a message is reported if the implementation of the
  function uses other global variables or does not uses every global
  variable listed in its declaration.  

o Memory management errors.  Instances where storage that has been
  deallocated is used, or where storage is not deallocated (memory leaks).

o Dangerous data sharing or unexpected aliasing.  Parameters to a
  function share storage in a way that may lead to undefined or undesired
  behavior, or a reference to storage within the representation of an
  abstract type is created.  

o Using possibly undefined storage or returning storage that is not
  completely defined (except as documented).  

o Dereferencing a possibly null pointer.  

o Dangerous macro implementations or invocations. 

o Violations of customizable naming conventions. 

o Program behavior that is undefined because it depends on order of
  evaluation, likely infinite loops, fall-through cases, incomplete logic,
  statements with no effect, ignored return values, unused declarations,
  and exceeding certain standard limits.  

LCLint checking can be customized to select what classes of errors are
reported using command line flags and stylized comments in the code.

For more information, please visit the LCLint home page at

    http://larch-www.lcs.mit.edu:8001/larch/lclint/

We are very interested in hearing about your experiences using LCLint.
Send any questions or comments to lclint@larch.lcs.mit.edu.

There are two mailing lists associated with LCLint:

   lclint-announce@larch.lcs.mit.edu

      Reserved for announcements of new releases and bug fixes.

   lclint-interest@larch.lcs.mit.edu

      Informal discussions on the use and development of lclint.

Send a (human-readable) message to lclint-request@larch.lcs.mit.edu to
subscribe to a list.  Everyone who uses lclint should subscribe to
lclint-announce, to be informed of new releases.

Build Instructions
==================

To build LCLint you need:

   * a (hopefully ANSI-conforming) C compiler. On most modern Unix systems,
     cc will work fine. For older or less standard systems, gcc is
     recommended.
   * gmake, the GNU make utility. If you don't have gmake installed on your
     system, download it from prep.ai.mit.edu.
   * standard Unix tools: uncompress or gzip compression utility, tar
     archive utility, csh command shell.

Build Instructions:

Download the LCLint source package (lclint.src.tar.gz).

Copy this package to the directory where you want to build LCLint.  When
the tar file is extracted, it will create an lclint subdirectory in this
directory.

Uncompress the package. If you downloaded the gzip package, run: 
      gzip -d lclint.src.tar.gz 

Extract files from the tar archive. Run tar xf lclint.src.tar. This will
create an lclint directory, containing several subdirectories.

Run configure. This will create a Makefile with settings for your
system. If you want to install LCLint or associated libraries different
directories, edit the Makefile.

Run gmake. It is best to do this in an emacs shell or a buffered
terminal, so you can scroll through the output.

Run gmake test. Check test output. If there are errors, send a bug
report to lclint-bug@larch.lcs.mit.edu

