README

Release notes for Valgrind, snapshot 20020217
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

KDE3 developers: please read also README_KDE3_FOLKS for guidance
about how to debug KDE3 applications with Valgrind.

For instructions on how to build/install, see the end of this file.


Executive Summary
~~~~~~~~~~~~~~~~~
Valgrind is a tool to help you find memory-management problems in your
programs. When a program is run under Valgrind's supervision, all
reads and writes of memory are checked, and calls to
malloc/new/free/delete are intercepted. As a result, Valgrind can
detect problems such as:

   Use of uninitialised memory 
   Reading/writing memory after it has been free'd 
   Reading/writing off the end of malloc'd blocks 
   Reading/writing inappropriate areas on the stack 
   Memory leaks -- where pointers to malloc'd blocks are lost forever
   Passing of uninitialised and/or unaddressible memory to system calls
   Mismatched use of malloc/new/new [] vs free/delete/delete [] 

Problems like these can be difficult to find by other means, often
lying undetected for long periods, then causing occasional,
difficult-to-diagnose crashes.

When Valgrind detects such a problem, it can, if you like, attach GDB
to your program, so you can poke around and see what's going on.

Valgrind is closely tied to details of the CPU, operating system and
to a less extent, compiler and basic C libraries. This makes it
difficult to make it portable, so I have chosen at the outset to
concentrate on what I believe to be a widely used platform: Red Hat
Linux 7.2, on x86s. I believe that it will work without significant
difficulty on other x86 GNU/Linux systems which use the 2.4 kernel and
GNU libc 2.2.X, for example SuSE 7.1 and Mandrake 8.0.  Red Hat 6.2 is
also supported.  It has worked in the past, and probably still does,
on RedHat 7.1 and 6.2.  Note that I haven't compiled it on RedHat 7.1
and 6.2 for a while, so they may no longer work now.

Valgrind is licensed under the GNU General Public License, version 2. 
Read the file LICENSE in the source distribution for details.


Documentation
~~~~~~~~~~~~~
A comprehensive user guide is supplied.  Point your browser at
docs/index.html.  If your browser doesn't like frames, point it
instead at docs/manual.html.


Building and installing it
~~~~~~~~~~~~~~~~~~~~~~~~~~

If you install from CVS :

  0. cd into the source directory

  1. Run ./autogen.sh to setup the environment (you need the standard
     autoconf tools to do so)

If you install from a tar.gz archive:

  2. Run ./configure, with some options if you wish. The standard
     options are documented in the INSTALL file.

  3. Do "make"

  4. As root, do "make install"

  5. See if it works.  Try "valgrind ls -l".  Either this works,
     or it bombs out complaining it can't find argc/argv/envp.
     If this happens, you'll have to futz around with 
     vg_main.c:710 to vg_main.c:790 to try and find suitable offsets.
     It's not hard; many have been successful here.

Once step 5 is successful, you can now use valgrind.  Documentation
is in docs/manual.html.  The following auxiliary steps may enhance
your valgrinding experience, though.

6.  Create a file containing  enough suppressions so that

       valgrind xedit

    runs without generating any errors.  This means you've more
    or less suppressed all the scummy errors from the X11 base
    libraries and from glibc, which will make it easier to spot
    genuine errors in your own code. The default.supp file
    should contains a good starting point. Do *not* edit this file
    however, as it will be overwritten at the next installation of
    valgrind, but create your own local.supp file.


Julian Seward (jseward@acm.org)
15 Feb 2002