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9377cf0ea5
info (DW_CFA_def_cfa_expression, DW_CFA_expression, DW_CFA_val_expression). Mechanism to support all of these is in place although only DW_CFA_val_expression is currently connected up. This is really nasty. The basic idea is to partially evaluate each expression at the debuginfo-reading time by running it on a stack machine in which each stack element is an expression tree. If the expression can be 'run' successfully, the tree (dag, really) remaining at the top of the stack is massaged and put into the DiCfSI record for that address range. At unwind time the tree is evaluated if needed. Such cases are in fact extremely rare and so the vast majority of unwindings use the same mechanism as before. As a result of all this: * some obscure cases in glibc-2.5's libpthread.so unwind when they didn't before * --debug-dump=frames produces identical output to that of readelf for libc-2.5.so and associated libpthread.so * All the action centers around the new type CfiExpr, which is a union expression-tree type in the same style as IRExpr et al * Many dark corners of the CFI reader have been looked at and (re-)validated git-svn-id: svn://svn.valgrind.org/valgrind/trunk@6620
Release notes for Valgrind
~~~~~~~~~~~~~~~~~~~~~~~~~~
If you are building a binary package of Valgrind for distribution,
please read README_PACKAGERS. It contains some important information.
If you are developing Valgrind, please read README_DEVELOPERS. It contains
some useful information.
For instructions on how to build/install, see the end of this file.
Valgrind works on most, reasonably recent Linux setups. If you have
problems, consult FAQ.txt to see if there are workarounds.
Executive Summary
~~~~~~~~~~~~~~~~~
Valgrind is an award-winning suite of tools for debugging and profiling
Linux programs. With the tools that come with Valgrind, you can
automatically detect many memory management and threading bugs, avoiding
hours of frustrating bug-hunting, making your programs more stable. You can
also perform detailed profiling, to speed up and reduce memory use of your
programs.
The Valgrind distribution currently includes four tools: a memory error
detector, a thread error detector, a cache profiler and a heap profiler.
To give you an idea of what Valgrind tools do, when a program is run
under the supervision of Memcheck, the memory error detector tool, all
reads and writes of memory are checked, and calls to malloc/new/free/delete
are intercepted. As a result, Memcheck can detect if your program:
- Accesses memory it shouldn't (areas not yet allocated, areas that have
been freed, areas past the end of heap blocks, inaccessible areas of
the stack).
- Uses uninitialised values in dangerous ways.
- Leaks memory.
- Does bad frees of heap blocks (double frees, mismatched frees).
- Passes overlapping source and destination memory blocks to memcpy() and
related functions.
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 one of these errors occurs, you can
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. Nonetheless, it is available for
the following platforms: x86/Linux, AMD64/Linux and PPC32/Linux.
Valgrind is licensed under the GNU General Public License, version 2.
Read the file COPYING in the source distribution for details.
Documentation
~~~~~~~~~~~~~
A comprehensive user guide is supplied. Point your browser at
$PREFIX/share/doc/valgrind/manual.html, where $PREFIX is whatever you
specified with --prefix= when building.
Building and installing it
~~~~~~~~~~~~~~~~~~~~~~~~~~
To install from the Subversion repository :
0. Check out the code from SVN, following the instructions at
http://www.valgrind.org/downloads/repository.html.
1. cd into the source directory.
2. Run ./autogen.sh to setup the environment (you need the standard
autoconf tools to do so).
3. Continue with the following instructions...
To install from a tar.bz2 distribution:
4. Run ./configure, with some options if you wish. The standard
options are documented in the INSTALL file. The only interesting
one is the usual --prefix=/where/you/want/it/installed.
5. Do "make".
6. Do "make install", possibly as root if the destination permissions
require that.
7. See if it works. Try "valgrind ls -l". Either this works, or it
bombs out with some complaint. In that case, please let us know
(see www.valgrind.org).
Important! Do not move the valgrind installation into a place
different from that specified by --prefix at build time. This will
cause things to break in subtle ways, mostly when Valgrind handles
fork/exec calls.
The Valgrind Developers