C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Should exceptions be thrown by value or reference?          C++Talk.NET Forum Index -> C++ language (comp.lang.c++) View previous topic :: View next topic   Author Message Rennie deGraaf Guest Posted: Mon Feb 28, 2005 12:55 am    Post subject: Should exceptions be thrown by value or reference? Is it better/more efficient to throw exceptions by value, as in void func() throw (SomeException) { // do some stuff throw SomeException("error message"); } void bar() { try { foo() } catch (SomeException e) { // do some stuff } } or by reference, as in void func() throw (SomeException*) { // do some stuff throw new SomeException("error message"); } void bar() { try { foo() } catch (SomeException* e) { // do some stuff delete e; } } ? Either method requires allocating memory (on the stack in the first case, on the heap in the second), so I don't think that either is any less safe than the other. Obviously, the method of throwing pointers is prone to memory leaks if programmers are not careful, but is it any more or less efficient? Rennie Back to top Ioannis Vranos Guest Posted: Mon Feb 28, 2005 1:26 am    Post subject: Re: Should exceptions be thrown by value or reference? Rennie deGraaf wrote: Quote: Is it better/more efficient to throw exceptions by value, as in void func() throw (SomeException) { // do some stuff throw SomeException("error message"); } void bar() { try { foo() } catch (SomeException e) { // do some stuff } } or by reference, as in void func() throw (SomeException*) { // do some stuff throw new SomeException("error message"); } void bar() { try { foo() } catch (SomeException* e) { // do some stuff delete e; } } or void func() throw (SomeException) { // do some stuff throw SomeException("error message"); } void bar() { try { func(); } catch (SomeException &re) { // do some stuff } } Quote: ? Either method requires allocating memory (on the stack in the first case, on the heap in the second), so I don't think that either is any less safe than the other. Obviously, the method of throwing pointers is prone to memory leaks if programmers are not careful, but is it any more or less efficient? By reference (with references or pointers) is of course more space and time efficient since no new exception object is created. In non-GC systems, I would prefer references. -- Ioannis Vranos http://www23.brinkster.com/noicys Back to top Cy Edmunds Guest Posted: Mon Feb 28, 2005 1:32 am    Post subject: Re: Should exceptions be thrown by value or reference? "Rennie deGraaf" <ca.ucalgary.cpsc@degraaf> wrote Quote: Is it better/more efficient to throw exceptions by value, as in void func() throw (SomeException) Read this before you use exception specifications: http://www.gotw.ca/publications/mill22.htm Quote: { // do some stuff throw SomeException("error message"); } Otherwise this is OK, especially if SomeException is ultimately derived from std::exception. Quote: void bar() { try { foo() } catch (SomeException e) { // do some stuff } } This is OK but don't expect any sort of polymorphic behavior. If you derive another class from SomeException it will get bit sliced down to a SomeException unless you change your catch phrase to catch (SomeException &e) Quote: or by reference, as in void func() throw (SomeException*) { // do some stuff throw new SomeException("error message"); } I can't imagine why anyone would do this. Quote: void bar() { try { foo() } catch (SomeException* e) { // do some stuff delete e; } } ? Either method requires allocating memory (on the stack in the first case, on the heap in the second), so I don't think that either is any less safe than the other. Obviously, the method of throwing pointers is prone to memory leaks if programmers are not careful, but is it any more or less efficient? Rennie I don't understand why everyone is so concerned about efficiency in a situation (propogation of an error) which one would certainly hope would constitute an extremely small portion of the run time. -- Cy http://home.rochester.rr.com/cyhome/ Back to top Ioannis Vranos Guest Posted: Mon Feb 28, 2005 2:25 am    Post subject: Re: Should exceptions be thrown by value or reference? Cy Edmunds wrote: Quote: I don't understand why everyone is so concerned about efficiency in a situation (propogation of an error) which one would certainly hope would constitute an extremely small portion of the run time. Basically where exceptions "by reference" (references or pointers) make sense are on severely run-time/space constrained systems, when exception types have no public copy constructors, and in GC systems I guess - in ..NET in addition to the usual unmanaged ISO C++ exception styles that were mentioned here, managed exceptions are created in the managed heap and caught as managed pointers: try { throw __gc new SomeException; } catch(SomeException *pe) { // ... } -- Ioannis Vranos http://www23.brinkster.com/noicys Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         C++Talk.NET Forum Index -> C++ language (comp.lang.c++) All times are GMT Page 1 of 1   Jump to: Select a forum C/C++----------------C LanguageC Language (Moderated)C++ Language (Moderated)C++ language (comp.lang.c++)C++ language, library and standards Non-English C/C++ Newsgroups----------------C++ (German)C++ (French)  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.