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84 lines
3.1 KiB
Plaintext
84 lines
3.1 KiB
Plaintext
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19 June 2002
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The purpose of this small doc is to guide you in using Valgrind to
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find and fix memory management bugs in KDE3.
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---------------------------------------------------
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Here's a getting-started-quickly checklist. It might sound daunting,
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but once set up things work fairly well.
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* You need an x86 box running a Linux 2.2 or 2.4 kernel, with glibc
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2.1.X or 2.2.X and XFree86 3.X or 4.X. In practice this means
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practically any recent Linux distro. Valgrind is developed on a
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vanilla Red Hat 7.2 installation, so at least works ok there.
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I imagine Mandrake 8 and SuSE 7.X would be ok too. It is known to
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work on Red Hats 6.2, 7.2 and 7.3, at the very least.
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* You need a reasonably fast machine, since programs run 25-100 x
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slower on Valgrind. I work with a 1133 MHz PIII with 512 M of
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memory. Interactive programs like kate, konqueror, etc, are
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usable, but in all, the faster your machine, the more useful
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valgrind will be.
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* You need at least 256M of memory for reasonable behaviour. Valgrind
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inflates the memory use of KDE apps approximately 3-4 x, so (eg)
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konqueror needs ~ 140M of memory to get started, although to be fair,
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at least 40 M of that is due to reading the debug info -- this is for
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a konqueror and all libraries built with -O -g.
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* You need to compile the KDE to be debugged, using a decent gcc/g++:
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- gcc 2.96-*, which comes with Red Hat 7.2, is buggy. It sometimes
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generates code with reads below %esp, even for simple functions.
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This means you will be flooded with errors which are nothing to
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do with your program. You can use the --workaround-gcc296-bugs=yes
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flag to ignore them. See the manual for details; this is not really
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a good solution.
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- I recommend you use gcc/g++ 2.95.3. It seems to compile
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KDE without problems, and does not suffer from the above bug. It's
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what I have been using.
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- gcc-3. 3.0.4 was observed to have a scheduling bug causing it to
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occasionally generate writes below the stack pointer. gcc-3.1 seems
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better in that respect.
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It's ok to build Valgrind with the default gcc on Red Hat 7.2.
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* So: build valgrind -- see the README file. It's the standard
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./configure ; make ; make install deal.
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* Build as much of KDE+Qt as you can with -g and without -O, for
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the usual reasons.
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* Use it!
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/path/to/valgrind $KDEDIR/bin/kate
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(or whatever).
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* If you are debugging KDE apps, be prepared for the fact that
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Valgrind finds bugs in the underlying Qt (qt-copy from CVS) too.
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* Please read the Valgrind manual, docs/index.html. It contains
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considerable details about how to use it, what's really going on,
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etc.
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* There are some significant limitations:
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- No MMX, SSE, SSE2 insns. Basically a 486 instruction set only.
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- Various other minor limitations listed in the manual.
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* If you have trouble with it, please let me know (jseward@acm.org)
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and I'll see if I can help you out.
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Have fun! If you find Valgrind useful in finding and fixing bugs,
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I shall consider my efforts to have been worthwhile.
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Julian Seward (jseward@acm.org)
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