C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Catching access violation exceptions Goto page 1, 2  Next          C++Talk.NET Forum Index -> C++ language (comp.lang.c++) View previous topic :: View next topic   Author Message Steven Reddie Guest Posted: Mon Sep 29, 2003 5:33 am    Post subject: Catching access violation exceptions I understand that access violations aren't part of the standard C++ exception handling support. On Windows, a particular MSVC compiler option enables Microsoft's Structured Exception Handling (SEH) in C++ EH so that a catch (...) will catch an access violation. I don't know if other platforms support something similar. I'm wondering about how to best protect an application or library from poorly written user-defined callbacks. It would be nice to be able to automatically unregister a user-defined callback if it is found to cause any exception including access violations. Does anyone know of a platform-independant method for achieving this? Regards and TIA, Steven Back to top Mike Wahler Guest Posted: Mon Sep 29, 2003 6:05 am    Post subject: Re: Catching access violation exceptions "Steven Reddie" <smr (AT) essemer (DOT) com.au> wrote Quote: I understand that access violations aren't part of the standard C++ exception handling support. OK. On Windows, a particular MSVC compiler Quote: option enables Microsoft's Structured Exception Handling (SEH) in C++ EH so that a catch (...) will catch an access violation. I don't know if other platforms support something similar. I'm wondering about how to best protect an application or library from poorly written user-defined callbacks. It would be nice to be able to automatically unregister a user-defined callback if it is found to cause any exception including access violations. Does anyone know of a platform-independant method for achieving this? How could there be? Do you think all platforms even define 'access violation'? E.g. remember MS-DOS, where you could poke a stick anywhere you liked? Sometimes you'd detonate a mine with the stick, and the OS just 'went away'. No 'access violation', no error message, nothing. Do you think those platforms that do define 'access violation' mean the same thing by that term? -Mike Back to top Alexander Terekhov Guest Posted: Mon Sep 29, 2003 8:00 am    Post subject: Re: Catching access violation exceptions Steven Reddie wrote: Quote: I understand that access violations aren't part of the standard C++ exception handling support. On Windows, a particular MSVC compiler option enables Microsoft's Structured Exception Handling (SEH) in C++ EH so that a catch (...) will catch an access violation. I don't know if other platforms support something similar. I'm wondering about how to best protect an application or library from poorly written user-defined callbacks. Don't use catch(...). Send an email to Abrahams/Sutter/... demanding a fix for C++ EH. They shall mandate 2-phase EH and amended exception specs (make ES work without totally silly catch(...)), to begin with. Things like bool expected_exception<T>() and bool unwinding(T *) can follow as well. regards, alexander. Back to top Gianni Mariani Guest Posted: Mon Sep 29, 2003 1:00 pm    Post subject: Re: Catching access violation exceptions Steven Reddie wrote: Quote: I understand that access violations aren't part of the standard C++ exception handling support. Right. On Windows, a particular MSVC compiler Quote: option enables Microsoft's Structured Exception Handling (SEH) in C++ EH so that a catch (...) will catch an access violation. I don't know if other platforms support something similar. No. This is platform dependant. Quote: I'm wondering about how to best protect an application or library from poorly written user-defined callbacks. You can't. If a process hits an access violation, you have no idea (other than in some very special circumstances) just how corrupted things are. It would be nice to be able to Quote: automatically unregister a user-defined callback if it is found to cause any exception including access violations. If data structures are in an inconsistant state, you're hosed. Does anyone know of Quote: a platform-independant method for achieving this? No. You could a library to do this but it's not a trivial task. Back to top Gianni Mariani Guest Posted: Mon Sep 29, 2003 1:47 pm    Post subject: Re: Catching access violation exceptions Alexander Terekhov wrote: Quote: Steven Reddie wrote: I understand that access violations aren't part of the standard C++ exception handling support. On Windows, a particular MSVC compiler option enables Microsoft's Structured Exception Handling (SEH) in C++ EH so that a catch (...) will catch an access violation. I don't know if other platforms support something similar. I'm wondering about how to best protect an application or library from poorly written user-defined callbacks. Don't use catch(...). Send an email to Abrahams/Sutter/... demanding a fix for C++ EH. They shall mandate 2-phase EH and amended exception specs (make ES work without totally silly catch(...)), to begin with. Things like bool expected_exception<T>() and bool unwinding(T *) can follow as well. How would that fix the OP problem ? Back to top Attila Feher Guest Posted: Mon Sep 29, 2003 1:50 pm    Post subject: Re: Catching access violation exceptions Alexander Terekhov wrote: [SNIP] Quote: Don't use catch(...). Send an email to Abrahams/Sutter/... demanding a fix for C++ EH. They shall mandate 2-phase EH and amended exception specs (make ES work without totally silly catch(...)), to begin with. Things like bool expected_exception<T>() and bool unwinding(T *) can follow as well. Care to explain? No links allowed, this is a text only newsgroup. And please *not* so briefly that noone will understand. -- Attila aka WW Back to top Ron Natalie Guest Posted: Mon Sep 29, 2003 2:18 pm    Post subject: Re: Catching access violation exceptions "Steven Reddie" <smr (AT) essemer (DOT) com.au> wrote Quote: I'm wondering about how to best protect an application or library from poorly written user-defined callbacks. It would be nice to be able to automatically unregister a user-defined callback if it is found to cause any exception including access violations. Does anyone know of a platform-independant method for achieving this? No. It can't be. The nature of hardware faults is very implementation specific. You'll have to investigate it for each platform. One thing you can tend to do portably is check for obvious errors like null pointers (even places where they ought not to be possible like the address of references or the "this" pointer in your member functions that are called from the outside). While undefined behavior has most certainly occurred, you can potentially limit it's impact. Back to top Alexander Terekhov Guest Posted: Mon Sep 29, 2003 2:23 pm    Post subject: Re: Catching access violation exceptions Gianni Mariani wrote: Quote: Alexander Terekhov wrote: Steven Reddie wrote: I understand that access violations aren't part of the standard C++ exception handling support. On Windows, a particular MSVC compiler option enables Microsoft's Structured Exception Handling (SEH) in C++ EH so that a catch (...) will catch an access violation. I don't know if other platforms support something similar. I'm wondering about how to best protect an application or library from poorly written user-defined callbacks. Don't use catch(...). Send an email to Abrahams/Sutter/... demanding a fix for C++ EH. They shall mandate 2-phase EH and amended exception specs (make ES work without totally silly catch(...)), to begin with. Things like bool expected_exception<T>() and bool unwinding(T *) can follow as well. How would that fix the OP problem ? Since there will be no catch(...) ["unprotected" via fixed ES] and no hurting unwinding (due to currently broken ES), it would cause any *unexpected* exception end up in the std::unexpected() invoked at throw point. By default, std::unexpected() calls abort(). I forgot to mention that he should send an email to Sutter demanding "SEH_exception" base class (it can even derive from std::exception, as far as I'm concerned). regards, alexander. Back to top Gianni Mariani Guest Posted: Mon Sep 29, 2003 2:38 pm    Post subject: Re: Catching access violation exceptions [OT] Alexander Terekhov wrote: Quote: Gianni Mariani wrote: .... How would that fix the OP problem ? Since there will be no catch(...) ["unprotected" via fixed ES] and no hurting unwinding (due to currently broken ES), it would cause any *unexpected* exception end up in the std::unexpected() invoked at throw point. By default, std::unexpected() calls abort(). I forgot to mention that he should send an email to Sutter demanding "SEH_exception" base class (it can even derive from std::exception, as far as I'm concerned). Apart from being off-topic on both the thread AND the NG; I think exceptions are intended by the standard to be very simplistic. Remember, these are a replacement of the setjmp/longjmp semantics which had all kinds of disasters if you didn't know what you were doing. I think if your application is unable to work correctly with EH as defined by the standard, then EH may not be the right solution for you. Back to top Alexander Terekhov Guest Posted: Mon Sep 29, 2003 2:54 pm    Post subject: Re: Catching access violation exceptions [OT] Gianni Mariani wrote: [...] Quote: Remember, these are a replacement of the setjmp/longjmp semantics which had all kinds of disasters if you didn't know what you were doing. On modern systems, setjmp() kinda "injects" a handler and longjmp simply unwinds and transfers control to it (causing the second setjmp's return). They call it "forced unwinding". The only problem with forced unwinding is that it doesn't work nice with... surprise, surprise... *catch(...)*. The right approach here is to have a known "jump" exception, of course. Quote: I think if your application is unable to work correctly with EH as defined by the standard, then EH may not be the right solution for you. EH as defined by the current standard is pretty much broken and is nothing but a compromise influenced by "rumors" that <quote> On other systems, it is architecturally close to impossible not to invoke the destructors while searching for a handler </quote> (Pg. 381, TC++PL [my pdf version]) http://groups.google.com/groups?selm=3EEB527C.9D72630%40web.de (Subject: Re: std0X::expected_exception<T>()) regards, alexander. Back to top Christopher Benson-Manica Guest Posted: Mon Sep 29, 2003 7:53 pm    Post subject: [OT] DOS Mike Wahler <mkwahler (AT) mkwahler (DOT) net> spoke thus: Quote: E.g. remember MS-DOS, where you could poke a stick anywhere you liked? Sometimes you'd detonate a mine with the stick, and the OS just 'went away'. No 'access violation', no error message, nothing. I'd be interested to hear more about this phenomenon... If you'd prefer, you can e-mail me (minus spamtrap, of course). -- Christopher Benson-Manica | Jumonji giri, for honour. ataru(at)cyberspace.org | Back to top Mike Wahler Guest Posted: Mon Sep 29, 2003 8:21 pm    Post subject: Re: [OT] DOS "Christopher Benson-Manica" <ataru (AT) nospam (DOT) cyberspace.org> wrote Quote: Mike Wahler <mkwahler (AT) mkwahler (DOT) net> spoke thus: E.g. remember MS-DOS, where you could poke a stick anywhere you liked? Sometimes you'd detonate a mine with the stick, and the OS just 'went away'. No 'access violation', no error message, nothing. I'd be interested to hear more about this phenomenon... If you'd prefer, you can e-mail me (minus spamtrap, of course). 'Quick-n-dirty explanation': MDSOS is an 'unprotected' operating system, thus does not monitor and restrict access to memory or peripheral devices like e.g. Windows does. You could directly access and/or modify (e.g. from assembly, C, BASIC, or whatever language), all of memory space (including the ubiquitous 'interrupt vectors'), hardware registers, etc. Sometimes 'convenient' and almost always faster than making OS calls, but deadly if you do it wrong. MSDOS doesn't have conditions like 'access violations' or 'seg faults' etc. and will let you scribble around anywhere you like inside its internals. If you want more details, when I get time, I can email you a more detailed description. Let me know. -Mike Back to top Steven Reddie Guest Posted: Tue Sep 30, 2003 1:00 pm    Post subject: Re: Catching access violation exceptions Thanks all for the responses. "Mike Wahler" <mkwahler (AT) mkwahler (DOT) net> wrote Quote: "Steven Reddie" <smr (AT) essemer (DOT) com.au> wrote in message news:f93791bd.0309282133.650da850 (AT) posting (DOT) google.com... I'm wondering about how to best protect an application or library from poorly written user-defined callbacks. It would be nice to be able to automatically unregister a user-defined callback if it is found to cause any exception including access violations. Does anyone know of a platform-independant method for achieving this? How could there be? Do you think all platforms even define 'access violation'? Mike, why is that significant? ANSI C defines a signal() function that can catch these things. That's the job of the compiler/libraries, to make system dependencies useable in a system independent way. Quote: E.g. remember MS-DOS, where you could poke a stick anywhere you liked? Sometimes you'd detonate a mine with the stick, and the OS just 'went away'. No 'access violation', no error message, nothing. Do you think those platforms that do define 'access violation' mean the same thing by that term? Sure, I remember such things, and know that 'access violation' may mean different things on different platforms, alignment exceptions will never occur on some platforms, and writing to the wrong address may not even cause an exception if the address is valid, however such things are no reason why a platform independent method for catching platform dependent exceptions with a catch(...) is impossible. I'm not asking to be able to identify the type of exception, just a way to catch them so that I can avoid calling the function in future that caused the exception. However, that said, it would still be possible to define some accessviolation_exception and alignment_exception types and throw only the ones that make sense to a particular system. Regards, Steven Back to top Juergen Heinzl Guest Posted: Tue Sep 30, 2003 1:29 pm    Post subject: Re: Catching access violation exceptions In article <f93791bd.0309282133.650da850 (AT) posting (DOT) google.com>, Steven Reddie wrote: Quote: I understand that access violations aren't part of the standard C++ exception handling support. On Windows, a particular MSVC compiler option enables Microsoft's Structured Exception Handling (SEH) in C++ EH so that a catch (...) will catch an access violation. I don't know if other platforms support something similar. I'm wondering about how to best protect an application or library from poorly written user-defined callbacks. It would be nice to be able to automatically unregister a user-defined callback if it is found to cause any exception including access violations. Does anyone know of a platform-independant method for achieving this? [-] No, not really. You can use whatever signal handling is available, though signals aren't a C++ thing. So staying off topic of this group for a little bit more IMHO the whole idea of trying to "fix" anything during runtime here isn't such a great idea either as a signal may be risen *after* some damage has been already done and so from there on all bets are off. Say should your application be some sort of flight control system please let me leave the plane *NOW*. Cheers, Juergen -- Real name : Juergen Heinzl no flames / EMail Private : [email]juergen (AT) manannan (DOT) org[/email] send money instead / Back to top Pete Becker Guest Posted: Tue Sep 30, 2003 2:13 pm    Post subject: Re: Catching access violation exceptions Steven Reddie wrote: Quote: Thanks all for the responses. "Mike Wahler" <mkwahler (AT) mkwahler (DOT) net> wrote "Steven Reddie" <smr (AT) essemer (DOT) com.au> wrote in message news:f93791bd.0309282133.650da850 (AT) posting (DOT) google.com... I'm wondering about how to best protect an application or library from poorly written user-defined callbacks. It would be nice to be able to automatically unregister a user-defined callback if it is found to cause any exception including access violations. Does anyone know of a platform-independant method for achieving this? How could there be? Do you think all platforms even define 'access violation'? Mike, why is that significant? ANSI C defines a signal() function that can catch these things. That's the job of the compiler/libraries, to make system dependencies useable in a system independent way. The only portable way to enter a signal handler is to call raise. Support for asynchronous signals (such as SIGSEGV) is not required. Quote: E.g. remember MS-DOS, where you could poke a stick anywhere you liked? Sometimes you'd detonate a mine with the stick, and the OS just 'went away'. No 'access violation', no error message, nothing. Do you think those platforms that do define 'access violation' mean the same thing by that term? Sure, I remember such things, and know that 'access violation' may mean different things on different platforms, alignment exceptions will never occur on some platforms, and writing to the wrong address may not even cause an exception if the address is valid, however such things are no reason why a platform independent method for catching platform dependent exceptions with a catch(...) is impossible. That's a good example of undefined behavior. If your implementation supports it, use it. But with the understanding that it isn't something you can count on. What more do you think the language definition should say? -- Pete Becker Dinkumware, Ltd. 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