README_DEVELOPERS

Building and not installing it
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
To run Valgrind without having to install it, run coregrind/valgrind
with the VALGRIND_LIB environment variable set, where <dir> is the root
of the source tree (and must be an absolute path).  Eg:

  VALGRIND_LIB=~/grind/head4/.in_place ~/grind/head4/coregrind/valgrind 

This allows you to compile and run with "make" instead of "make install",
saving you time.

Or, you can use the 'vg-in-place' script which does that for you.

I recommend compiling with "make --quiet" to further reduce the amount of
output spewed out during compilation, letting you actually see any errors,
warnings, etc.


Building a distribution tarball
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
To build a distribution tarball from the valgrind sources:

  make dist

In addition to compiling, linking and packaging everything up, the command
will also build the documentation. Even if all required tools for building the
documentation are installed, this step may not succeed because of hidden
dependencies. E.g. on Ubuntu you must have "docbook-xsl" installed.
Additionally, specific tool versions maybe needed.

If you only want to test whether the generated tarball is complete and runs
regression tests successfully, building documentation is not needed.
Edit docs/Makefile.am, search for BUILD_ALL_DOCS and follow instructions there.


Running the regression tests
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
To build and run all the regression tests, run "make [--quiet] regtest".

To run a subset of the regression tests, execute:

  perl tests/vg_regtest <name>

where <name> is a directory (all tests within will be run) or a single
.vgtest test file, or the name of a program which has a like-named .vgtest
file.  Eg:

  perl tests/vg_regtest memcheck
  perl tests/vg_regtest memcheck/tests/badfree.vgtest
  perl tests/vg_regtest memcheck/tests/badfree


Running the performance tests
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
To build and run all the performance tests, run "make [--quiet] perf".

To run a subset of the performance suite, execute:

  perl perf/vg_perf <name>

where <name> is a directory (all tests within will be run) or a single
.vgperf test file, or the name of a program which has a like-named .vgperf
file.  Eg:

  perl perf/vg_perf perf/
  perl perf/vg_perf perf/bz2.vgperf
  perl perf/vg_perf perf/bz2

To compare multiple versions of Valgrind, use the --vg= option multiple
times.  For example, if you have two Valgrinds next to each other, one in
trunk1/ and one in trunk2/, from within either trunk1/ or trunk2/ do this to
compare them on all the performance tests:

  perl perf/vg_perf --vg=../trunk1 --vg=../trunk2 perf/


Debugging Valgrind with GDB
~~~~~~~~~~~~~~~~~~~~~~~~~~~
To debug the valgrind launcher program (<prefix>/bin/valgrind) just
run it under gdb in the normal way.

Debugging the main body of the valgrind code (and/or the code for
a particular tool) requires a bit more trickery but can be achieved
without too much problem by following these steps:

(1) Set VALGRIND_LAUNCHER to point to the valgrind executable.  Eg:

      export VALGRIND_LAUNCHER=/usr/local/bin/valgrind

    or for an uninstalled version in a source directory $DIR:

      export VALGRIND_LAUNCHER=$DIR/coregrind/valgrind

(2) Run gdb on the tool executable.  Eg:

      gdb /usr/local/lib/valgrind/ppc32-linux/lackey

    or

      gdb $DIR/.in_place/x86-linux/memcheck

(3) Do "handle SIGSEGV SIGILL nostop noprint" in GDB to prevent GDB from
    stopping on a SIGSEGV or SIGILL:

    (gdb) handle SIGILL SIGSEGV nostop noprint

(4) Set any breakpoints you want and proceed as normal for gdb. The
    macro VG_(FUNC) is expanded to vgPlain_FUNC, so If you want to set
    a breakpoint VG_(do_exec), you could do like this in GDB:

    (gdb) b vgPlain_do_exec

(5) Run the tool with required options:

    (gdb) run pwd

Steps (1)--(3) can be put in a .gdbinit file, but any directory names must
be fully expanded (ie. not an environment variable).

A different and possibly easier way is as follows:

(1) Run Valgrind as normal, but add the flag --wait-for-gdb=yes.  This
    puts the tool executable into a wait loop soon after it gains
    control.  This delays startup for a few seconds.

(2) In a different shell, do "gdb /proc/<pid>/exe <pid>", where
    <pid> you read from the output printed by (1).  This attaches
    GDB to the tool executable, which should be in the abovementioned
    wait loop.

(3) Do "cont" to continue.  After the loop finishes spinning, startup
    will continue as normal.  Note that comment (3) above re passing
    signals applies here too.


Self-hosting
~~~~~~~~~~~~
To run Valgrind under Valgrind:

(1) Check out 2 trees, "Inner" and "Outer".  Inner runs the app
    directly.  Outer runs Inner.

(2) Configure inner with --enable-inner and build/install as
    usual.

(3) Configure Outer normally and build/install as usual.

(4) Choose a very simple program (date) and try

    outer/.../bin/valgrind --sim-hints=enable-outer --trace-children=yes  \
       --run-libc-freeres=no --tool=cachegrind -v \
       inner/.../bin/valgrind --vgdb-prefix=./inner --tool=none -v prog

If you omit the --trace-children=yes, you'll only monitor Inner's launcher
program, not its stage2. Outer needs --run-libc-freeres=no, as otherwise
it will try to find and run __libc_freeres in the inner, while libc is not
used by the inner. Inner needs --vgdb-prefix=./inner to avoid inner
gdbserver colliding with outer gdbserver.

Debugging the whole thing might imply to use up to 3 GDB:
  * a GDB attached to the Outer valgrind, allowing
    to examine the state of Outer.
  * a GDB using Outer gdbserver, allowing to
    examine the state of Inner.
  * a GDB using Inner gdbserver, allowing to
    examine the state of prog.

The whole thing is fragile, confusing and slow, but it does work well enough
for you to get some useful performance data.  Inner has most of
its output (ie. those lines beginning with "==<pid>==") prefixed with a '>',
which helps a lot.

At the time of writing the allocator is not annotated with client requests
so Memcheck is not as useful as it could be.  It also has not been tested
much, so don't be surprised if you hit problems.

When using self-hosting with an outer Callgrind tool, use '--pop-on-jump'
(on the outer). Otherwise, Callgrind has much higher memory requirements. 


Printing out problematic blocks
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
If you want to print out a disassembly of a particular block that
causes a crash, do the following.

Try running with "--vex-guest-chase-thresh=0 --trace-flags=10000000
--trace-notbelow=999999".  This should print one line for each block
translated, and that includes the address.

Then re-run with 999999 changed to the highest bb number shown.
This will print the one line per block, and also will print a
disassembly of the block in which the fault occurred.