On Thu, Jan 26, 2012 at 18:08, Yedidyah Bar-David < linux...@didi.bardavid.org> wrote:
> On Thu, Jan 26, 2012 at 10:54:56AM -0500, Ori Berger wrote: > > On 01/26/2012 10:16 AM, Baruch Siach wrote: > > > > >>Only by using valgrind, that I could find the exact location and figure > > >>out, that it was another function that had the problem. > > >> > > >>How does the modern memory management system is working then, that it > takes > > >>so much time for the problem to surface ? > > > > > >Now, if you corrupt the internal glibc data structure, glibc won't > notice > > >until you try to call one of malloc(), free(), etc. > > > > And in addition to what Baruch said: > > > > Valgrind will always catch these errors, but will result in > > significant slowdown (x10-x20). There are tools like DUMA (and its > > earlier incarnation, Electric Fence) incur almost no CPU overhead > > and can detect many kinds of corruptions as soon as they happen, by > > using the memory management units. > > > > (Because of the MMU granularity, you need to run your program twice > > - one in which allocations are aligned to the lower address, and one > > when they are aligned to the top address) > > > > There is also a middle ground; gcc's mudflap > > <http://www.stlinux.com/devel/debug/mudflap> and -- if your program > > is pure C and can be compiled by tcc, > > <http://bellard.org/tcc/tcc-doc.html#SEC21>; These are comparable to > > valgrind in functionality (for code you compile with them; standard > > library code runs at full speed/unchecked), but usually only > > introduce a small slowdown (10% or so). > > BTW, in case you do not know Fabric Bellard, he does lots of very cool > stuff - he is the author of qemu, and every now and then I give a look > at his site. I now did because of this post and found out an amazing > project of a PC Emulator in Javascript: > http://bellard.org/jslinux/ > The guy is simply amazing. > -- > Didi > Thank you all, you made me wiser :) Ido > > > _______________________________________________ > Linux-il mailing list > Linux-il@cs.huji.ac.il > http://mailman.cs.huji.ac.il/mailman/listinfo/linux-il >
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