Re: [Valgrind-users] How can valgrind prevent Segmentation fault?
I had a problem like last May, though it may not have been the same problem. In my case it was the optimization settings. I typically used -O0 for valgrind, and at -O0 the program didn’t crash. At level -O1 or higher it always crashed. I can’t recall if I ran it in valgrind at -O1 or higher, but if I did then that didn’t help me find the problem, either. In the end I combed through the code where the problem was occurring, and discovered that I had forgotten to return a value from a function that was declared to return bool. I hadn’t noticed the compiler warning in the 20 screens of Makefile messages that scrolled by. I hope that’s somehow helpful. john perry > On Jan 26, 2019, at 5:12 PM, Peng Yu wrote: > > Hi, > > I have an executable. If I just run on its own, there will be > segmentation fault. But if I run it using valgrind, it finishes > successfully. Does anybody how can this happen? How to debug such a > program? Thanks. > > -- > Regards, > Peng > > > ___ > Valgrind-users mailing list > Valgrind-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/valgrind-users ___ Valgrind-users mailing list Valgrind-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/valgrind-users
Re: [Valgrind-users] How can valgrind prevent Segmentation fault?
On 1/26/19, Eliot Moss wrote: On 1/26/2019, Peng Yu wrote: I have an executable. If I just run on its own, there will be segmentation fault. But if I run it using valgrind, it finishes successfully. Does anybody how can this happen? How to debug such a program? Thanks. Maybe not the sort of answer you have in mind, but I might start with using gdb. It should still segfault under those conditions. You can then try recompiling to -g to get debug symbols As Eliot says, SIGSEGV is easy. Run under gdb until the SIGSEGV occurs, then get a backtrace of subroutine calls, and look around. If necessary, then re-compile with -g to get more symbols. On modern Intel x86_64 hardware (or on a "friendly" virtual machine) and with lots of disk space, then try "Record and Replay": https://rr-project.org/ (The videos are excellent!) Re-played execution is *exactly* the same every time, so in the worst case then binary search on the number of executed instructions is a valid technique. 'rr' can even run the program "backwards", which is extremely useful. Stop at the error, put a breakpoint on the entry to the current subroutine, execute backwards to that breakpoint. Then step forward by statement or instruction, watching control flow, values of variables, etc. ___ Valgrind-users mailing list Valgrind-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/valgrind-users
Re: [Valgrind-users] How can valgrind prevent Segmentation fault?
A segfault is usually a bad pointer or something pointing outside allocated space. Why it stops segfaulting when you run it through Valgrind I don't know. Compile with -g for either Valgrind or gdb, and if it still runs in Valgrind try gdb. You can just do gdb then you'll probably have to type run in gdb. At least if it segfaults in there you can do a backtrace and maybe figure out why. Compiling with -g will usually enable gdb to print out bits of your code when it stops so you may recognize where it is. Google something like "gdb segfault tutorial", you usually have to pick a frame I think. hmm, umass, I used to work there until 2009. On 1/26/19, Eliot Moss wrote: > On 1/26/2019 6:12 PM, Peng Yu wrote: > >> I have an executable. If I just run on its own, there will be >> segmentation fault. But if I run it using valgrind, it finishes >> successfully. Does anybody how can this happen? How to debug such a >> program? Thanks. > > Maybe not the sort of answer you have in mind, but I might start > with using gdb. It should still segfault under those conditions. > You can then try recompiling to -g to get debug symbols. Doing > that might affect whether the bug exhibits, but it would make > debugging easier. > > Valgrind might be useful if you think the fault has to do with > improper freeing or lack of initialization of pointers ... > > Regards - Eliot Moss > > > ___ > Valgrind-users mailing list > Valgrind-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/valgrind-users > -- - No, I won't call it "climate change", do you have a "reality problem"? - AB1JX Cities are cages built to contain excess people and keep them from cluttering up nature. Impeach Impeach Impeach Impeach Impeach Impeach Impeach Impeach ___ Valgrind-users mailing list Valgrind-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/valgrind-users
Re: [Valgrind-users] How can valgrind prevent Segmentation fault?
On 1/26/2019 6:12 PM, Peng Yu wrote: I have an executable. If I just run on its own, there will be segmentation fault. But if I run it using valgrind, it finishes successfully. Does anybody how can this happen? How to debug such a program? Thanks. Maybe not the sort of answer you have in mind, but I might start with using gdb. It should still segfault under those conditions. You can then try recompiling to -g to get debug symbols. Doing that might affect whether the bug exhibits, but it would make debugging easier. Valgrind might be useful if you think the fault has to do with improper freeing or lack of initialization of pointers ... Regards - Eliot Moss ___ Valgrind-users mailing list Valgrind-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/valgrind-users
Re: [Valgrind-users] How can valgrind prevent Segmentation fault?
On Sat, 2019-01-26 at 17:12 -0600, Peng Yu wrote: > Hi, > > I have an executable. If I just run on its own, there will be > segmentation fault. But if I run it using valgrind, it finishes > successfully. Does anybody how can this happen? How to debug such a > program? Thanks. Is valgrind reporting some errors ? If yes, which kind of errors ? Philippe ___ Valgrind-users mailing list Valgrind-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/valgrind-users
[Valgrind-users] How can valgrind prevent Segmentation fault?
Hi, I have an executable. If I just run on its own, there will be segmentation fault. But if I run it using valgrind, it finishes successfully. Does anybody how can this happen? How to debug such a program? Thanks. -- Regards, Peng ___ Valgrind-users mailing list Valgrind-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/valgrind-users
