C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  "throw exp;" - Should terminate() be called if exp throws? Goto page 1, 2  Next          C++Talk.NET Forum Index -> C++ language, library and standards View previous topic :: View next topic   Author Message Kevin Goodsell Guest Posted: Mon Sep 29, 2003 5:14 am    Post subject: "throw exp;" - Should terminate() be called if exp throws? [This is a repost with some editing of a message I previously sent to gnu.g++.help. That message can be viewed here: http://groups.google.com/groups?selm=6Zlcb.1927%24NX3.713%40newsread3.news.pas.earthlink.net] In a recent thread in comp.lang.c++, we were discussing what should happen in the following case: #include <iostream> class Except { public: Except() { throw 1; } }; int main() { try { throw Except(); } catch (Except) { std::cout << "Caught Except" << std::endl; } catch (int) { std::cout << "Caught int" << std::endl; } return 0; } The thread can be viewed here: http://groups.google.com/groups?threadm=KGMbb.3867%24vS.1897%40newsread3.news.pas.earthlink.net Given this, at least one popular compiler generates code that calls terminate(). Earlier versions of that compiler and at least a few other popular compilers generate code that catches the int exception. I think catching the int is the correct thing to do, based on this (from a public draft): 15.5.1 The terminate() function [except.terminate] 1 In the following situations exception handling must be abandoned for less subtle error handling techniques: --when the exception handling mechanism, after completing evaluation of the expression to be thrown but before the exception is caught (_except.throw_), calls a user function that exits via an uncaught exception, 2 In such cases, void terminate(); is called (_lib.exception.terminate_). <snip> Gianni Mariani on comp.lang.c++ stated that he felt this was ambiguous, and questioned what could constitute completion of the expression to be thrown - in particular, could terminating evaluation the expression due to an exception be considered completing the expression? Guy Harrison on gnu.g++.help also suggested that the text was "vague". My questions for this group are: 1) What is the correct interpretation of that passage with respect to the above program? (Should it call terminate() or catch the int exception?) 2) Is this passage ambiguous? And if so, 3) should a defect report be filed? Thanks. -Kevin -- My email address is valid, but changes periodically. To contact me please use the address from a recent posting. --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ] Back to top David B. Held Guest Posted: Mon Sep 29, 2003 3:40 pm    Post subject: Re: "throw exp;" - Should terminate() be called if exp throw "Kevin Goodsell" <usenet1.spamfree.fusion (AT) neverbox (DOT) com> wrote Quote: [...] I think catching the int is the correct thing to do, based on this (from a public draft): 15.5.1 The terminate() function [except.terminate] 1 In the following situations exception handling must be abandoned for less subtle error handling techniques: --when the exception handling mechanism, after completing evaluation of the expression to be thrown but before the exception is caught (_except.throw_), calls a user function that exits via an uncaught exception, [...] It seems to me that the terminate() behaviour is correct. I'm not sure what "completing evaluation" means exactly, but certainly a "user function that exits via an uncaught exception" is being called "before the exception is caught." So it would appear that the intent here is to disallow this "throwing while throwing" behaviour, and call terminate(). I think the passage is not as clear as it could be, and certainly a note would help in interpretation, at the least. Dave --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system ([url]http://www.grisoft.com)[/url]. Version: 6.0.518 / Virus Database: 316 - Release Date: 9/11/2003 --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ] Back to top Randy Maddox Guest Posted: Mon Sep 29, 2003 3:43 pm    Post subject: Re: "throw exp;" - Should terminate() be called if exp throw [email]usenet1.spamfree.fusion (AT) neverbox (DOT) com[/email] (Kevin Goodsell) wrote in message news:<Md9db.5991$NX3.177 (AT) newsread3 (DOT) news.pas.earthlink.net>... Quote: [This is a repost with some editing of a message I previously sent to gnu.g++.help. That message can be viewed here: http://groups.google.com/groups?selm=6Zlcb.1927%24NX3.713%40newsread3.news.pas.earthlink.net] In a recent thread in comp.lang.c++, we were discussing what should happen in the following case: #include class Except { public: Except() { throw 1; } }; int main() { try { throw Except(); } catch (Except) { std::cout << "Caught Except" << std::endl; } catch (int) { std::cout << "Caught int" << std::endl; } return 0; } The thread can be viewed here: http://groups.google.com/groups?threadm=KGMbb.3867%24vS.1897%40newsread3.news.pas.earthlink.net Given this, at least one popular compiler generates code that calls terminate(). Earlier versions of that compiler and at least a few other popular compilers generate code that catches the int exception. I think catching the int is the correct thing to do, based on this (from a public draft): 15.5.1 The terminate() function [except.terminate] 1 In the following situations exception handling must be abandoned for less subtle error handling techniques: --when the exception handling mechanism, after completing evaluation of the expression to be thrown but before the exception is caught (_except.throw_), calls a user function that exits via an uncaught exception, There is also a footnote 134 referenced at the end of the line quoted above. That footnote provides an example of an object being thrown that has a copy ctor and states that if that ctor exits by throwing an exception then terminate() is called. It seems to me that your example is quite similar in that the ctor for the object being thrown exits by throwing an exception. Thus the Except object is never successfully constructed, the throw statement cannot be completed, and terminate() should be called. I do agree that the wording could be a bit clearer. Randy. Quote: other cases snipped 2 In such cases, void terminate(); is called (_lib.exception.terminate_). snip Gianni Mariani on comp.lang.c++ stated that he felt this was ambiguous, and questioned what could constitute completion of the expression to be thrown - in particular, could terminating evaluation the expression due to an exception be considered completing the expression? Guy Harrison on gnu.g++.help also suggested that the text was "vague". My questions for this group are: 1) What is the correct interpretation of that passage with respect to the above program? (Should it call terminate() or catch the int exception?) 2) Is this passage ambiguous? And if so, 3) should a defect report be filed? Thanks. -Kevin -- My email address is valid, but changes periodically. To contact me please use the address from a recent posting. --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ] Back to top Andrew Koenig Guest Posted: Tue Sep 30, 2003 5:34 am    Post subject: Re: "throw exp;" - Should terminate() be called if exp throw David> "Kevin Goodsell" <usenet1.spamfree.fusion (AT) neverbox (DOT) com> wrote in message David> news:Md9db.5991$NX3.177 (AT) newsread3 (DOT) news.pas.earthlink.net... Quote: [...] I think catching the int is the correct thing to do, based on this (from a public draft): 15.5.1 The terminate() function [except.terminate] 1 In the following situations exception handling must be abandoned for less subtle error handling techniques: --when the exception handling mechanism, after completing evaluation of the expression to be thrown but before the exception is caught (_except.throw_), calls a user function that exits via an uncaught exception, [...] David> It seems to me that the terminate() behaviour is correct. I'm David> not sure what "completing evaluation" means exactly, but David> certainly a "user function that exits via an uncaught David> exception" is being called "before the exception is caught." David> So it would appear that the intent here is to disallow this David> "throwing while throwing" behaviour, and call terminate(). I David> think the passage is not as clear as it could be, and certainly David> a note would help in interpretation, at the least. "Completing evaluation" means that the implementation has done everything it needs to do in order to determine the value of the expression. So, for example, if I execute throw foo(); and foo throws an exception, then that exception is thrown *before* completing evaluation of the expression "foo()". I don't see any reason why an exception that occurs while evaluting foo() should cause any behavior other than throwing that exception. -- Andrew Koenig, [email]ark (AT) acm (DOT) org[/email] --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ] Back to top David Abrahams Guest Posted: Tue Sep 30, 2003 5:34 am    Post subject: Re: "throw exp;" - Should terminate() be called if exp throw [email]rmaddox (AT) isicns (DOT) com[/email] (Randy Maddox) writes: Quote: usenet1.spamfree.fusion (AT) neverbox (DOT) com (Kevin Goodsell) wrote in message news:<Md9db.5991$NX3.177 (AT) newsread3 (DOT) news.pas.earthlink.net>... [This is a repost with some editing of a message I previously sent to gnu.g++.help. That message can be viewed here: I think catching the int is the correct thing to do, based on this (from a public draft): 15.5.1 The terminate() function [except.terminate] 1 In the following situations exception handling must be abandoned for less subtle error handling techniques: --when the exception handling mechanism, after completing evaluation of the expression to be thrown but before the exception is caught (_except.throw_), calls a user function that exits via an uncaught exception, There is also a footnote 134 referenced at the end of the line quoted above. That footnote provides an example of an object being thrown that has a copy ctor and states that if that ctor exits by throwing an exception then terminate() is called. It seems to me that your example is quite similar in that the ctor for the object being thrown exits by throwing an exception. But it's dissimilar in that the object whose constructor throws has not been thrown yet. That's the key point. Quote: Thus the Except object is never successfully constructed, the throw statement cannot be completed and terminate() should be called. Nor can the throw even be started, so the footnote is inapplicable. -- Dave Abrahams Boost Consulting www.boost-consulting.com --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ] Back to top David Abrahams Guest Posted: Tue Sep 30, 2003 5:45 pm    Post subject: Re: "throw exp;" - Should terminate() be called if exp throw [email]usenet1.spamfree.fusion (AT) neverbox (DOT) com[/email] (Kevin Goodsell) writes: Quote: My questions for this group are: 1) What is the correct interpretation of that passage with respect to the above program? (Should it call terminate() or catch the int exception?) It should catch the int exception. Quote: 2) Is this passage ambiguous? Not in the least, AFAICT. I can't imagine why people are saying that it is. An expression which constructs a temporary hasn't been completely evaluated until that temporary has been completely constructed. -- Dave Abrahams Boost Consulting www.boost-consulting.com --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ] Back to top David Abrahams Guest Posted: Tue Sep 30, 2003 5:45 pm    Post subject: Re: "throw exp;" - Should terminate() be called if exp throw [email]dheld (AT) codelogicconsulting (DOT) com[/email] ("David B. Held") writes: Quote: "Kevin Goodsell" <usenet1.spamfree.fusion (AT) neverbox (DOT) com> wrote in message news:Md9db.5991$NX3.177 (AT) newsread3 (DOT) news.pas.earthlink.net... [...] I think catching the int is the correct thing to do, based on this (from a public draft): 15.5.1 The terminate() function [except.terminate] 1 In the following situations exception handling must be abandoned for less subtle error handling techniques: --when the exception handling mechanism, after completing evaluation of the expression to be thrown but before the exception is caught (_except.throw_), calls a user function that exits via an uncaught exception, [...] It seems to me that the terminate() behaviour is correct. I'm not sure what "completing evaluation" means exactly It has the usual meaning. Except() is an expression constructing a temporary. Completing evaluating that expression means completing construction of the Except() object. Since the constructor throws, the construction never completes. In most ways, throw Except(); is no different from { Except x; throw x; } Quote: but certainly a "user function that exits via an uncaught exception" is being called "before the exception is caught." Not at all. That statement relies on circular reasoning. The user function (Except::Except()) does throw an exception, but the exception is caught. That exception is thrown "before the exception is throw", also, so the whole phrase doesn't apply. Quote: So it would appear that the intent here is to disallow this "throwing while throwing" behaviour The intent is to disallow throwing while unwinding. But in any case, the second "throwing" in "throwing while throwing" never happens, because the constructor doesn't complete. Quote: and call terminate(). I think the passage is not as clear as it could be, and certainly a note would help in interpretation, at the least. Maybe, but it seems to me all the information needed is in there, as long as we don't invent new meanings for "completing evaluation". -- Dave Abrahams Boost Consulting www.boost-consulting.com --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ] Back to top Gianni Mariani Guest Posted: Tue Sep 30, 2003 5:45 pm    Post subject: Re: "throw exp;" - Should terminate() be called if exp throw David Abrahams wrote: Quote: rmaddox (AT) isicns (DOT) com (Randy Maddox) writes: ... But it's dissimilar in that the object whose constructor throws has not been thrown yet. That's the key point. According to your statement above, the OP's code below should specifically exit 0 after writing "Caught int" right ? ..... #include <iostream> class Except { public: Except() { throw 1; } }; int main() { try { throw Except(); } catch (Except) { std::cout << "Caught Except" << std::endl; } catch (int) { std::cout << "Caught int" << std::endl; } return 0; } --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ] Back to top Gianni Mariani Guest Posted: Tue Sep 30, 2003 5:45 pm    Post subject: Re: "throw exp;" - Should terminate() be called if exp throw Andrew Koenig wrote: Quote: David> "Kevin Goodsell" <usenet1.spamfree.fusion (AT) neverbox (DOT) com> wrote in message David> news:Md9db.5991$NX3.177 (AT) newsread3 (DOT) news.pas.earthlink.net... [...] I think catching the int is the correct thing to do, based on this (from a public draft): 15.5.1 The terminate() function [except.terminate] 1 In the following situations exception handling must be abandoned for less subtle error handling techniques: --when the exception handling mechanism, after completing evaluation of the expression to be thrown but before the exception is caught (_except.throw_), calls a user function that exits via an uncaught exception, [...] David> It seems to me that the terminate() behaviour is correct. I'm David> not sure what "completing evaluation" means exactly, but David> certainly a "user function that exits via an uncaught David> exception" is being called "before the exception is caught." David> So it would appear that the intent here is to disallow this David> "throwing while throwing" behaviour, and call terminate(). I David> think the passage is not as clear as it could be, and certainly David> a note would help in interpretation, at the least. "Completing evaluation" means that the implementation has done everything it needs to do in order to determine the value of the expression. So, for example, if I execute throw foo(); and foo throws an exception, then that exception is thrown *before* completing evaluation of the expression "foo()". I don't see any reason why an exception that occurs while evaluting foo() should cause any behavior other than throwing that exception. The above is a very reasonable interpretation of "completing evaluation". However, there may be another, albeit possibly less reasonable, interpretation that the expression "completed" evaluation at the point that the exception is thrown. It would seem to me that if the writer intended to allow for the throw expression for itself to attempt to throw a second or more exceptions, that would have been explicitly spelled out. IMHO, I think a small clarification defect should be considered. --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ] Back to top David Abrahams Guest Posted: Thu Oct 02, 2003 10:13 pm    Post subject: Re: "throw exp;" - Should terminate() be called if exp throw [email]gi2nospam (AT) mariani (DOT) ws[/email] (Gianni Mariani) writes: Quote: David Abrahams wrote: [email]rmaddox (AT) isicns (DOT) com[/email] (Randy Maddox) writes: .. But it's dissimilar in that the object whose constructor throws has not been thrown yet. That's the key point. According to your statement above, the OP's code below should specifically exit 0 after writing "Caught int" right ? Right. -- Dave Abrahams Boost Consulting www.boost-consulting.com --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ] Back to top Randy Maddox Guest Posted: Thu Oct 02, 2003 10:14 pm    Post subject: Re: "throw exp;" - Should terminate() be called if exp throw [email]dave (AT) boost-consulting (DOT) com[/email] (David Abrahams) wrote in message news:<usmmfzug6.fsf (AT) boost-consulting (DOT) com>... Quote: usenet1.spamfree.fusion (AT) neverbox (DOT) com (Kevin Goodsell) writes: My questions for this group are: 1) What is the correct interpretation of that passage with respect to the above program? (Should it call terminate() or catch the int exception?) It should catch the int exception. 2) Is this passage ambiguous? Not in the least, AFAICT. I can't imagine why people are saying that it is. An expression which constructs a temporary hasn't been completely evaluated until that temporary has been completely constructed. -- Dave Abrahams Boost Consulting www.boost-consulting.com Let me summarize just to make sure I understand what is going on. 1) The statement "throw Except()" does not complete because the ctor for Except() exits by throwing an exception. Thus there is no issue with an exception being thown during unwinding because the "throw Except()" statement never completes. 2) The ctor for Except throws an int exception, which should then be caught by the corresponding catch() statement. 3) The difference between this case and the footnote about an exception thrown by an exception object's copy ctor is that in the latter case the initial throw statement has completed so that the copy ctor exception does occur in the context of stack unwinding, or at least in the context of an already active exception that has not yet been handled. Is that correct? Thanks. Randy. --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ] Back to top David Abrahams Guest Posted: Thu Oct 02, 2003 11:57 pm    Post subject: Re: "throw exp;" - Should terminate() be called if exp throw [email]rmaddox (AT) isicns (DOT) com[/email] (Randy Maddox) writes: Quote: dave (AT) boost-consulting (DOT) com (David Abrahams) wrote in message news:<usmmfzug6.fsf (AT) boost-consulting (DOT) com>... [email]usenet1.spamfree.fusion (AT) neverbox (DOT) com[/email] (Kevin Goodsell) writes: My questions for this group are: 1) What is the correct interpretation of that passage with respect to the above program? (Should it call terminate() or catch the int exception?) It should catch the int exception. 2) Is this passage ambiguous? Not in the least, AFAICT. I can't imagine why people are saying that it is. An expression which constructs a temporary hasn't been completely evaluated until that temporary has been completely constructed. Let me summarize just to make sure I understand what is going on. 1) The statement "throw Except()" does not complete because the ctor for Except() exits by throwing an exception. Thus there is no issue with an exception being thown during unwinding because the "throw Except()" statement never completes. 2) The ctor for Except throws an int exception, which should then be caught by the corresponding catch() statement. 3) The difference between this case and the footnote about an exception thrown by an exception object's copy ctor is that in the latter case the initial throw statement has completed so that the copy ctor exception does occur in the context of stack unwinding, or at least in the context of an already active exception that has not yet been handled. Is that correct? Precisely. -- Dave Abrahams Boost Consulting www.boost-consulting.com --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ] Back to top Randy Maddox Guest Posted: Fri Oct 03, 2003 4:01 pm    Post subject: Re: "throw exp;" - Should terminate() be called if exp throw [email]dave (AT) boost-consulting (DOT) com[/email] (David Abrahams) wrote in message news:<uad8jl0t1.fsf (AT) boost-consulting (DOT) com>... Quote: rmaddox (AT) isicns (DOT) com (Randy Maddox) writes: [email]dave (AT) boost-consulting (DOT) com[/email] (David Abrahams) wrote in message news:<usmmfzug6.fsf (AT) boost-consulting (DOT) com>... [email]usenet1.spamfree.fusion (AT) neverbox (DOT) com[/email] (Kevin Goodsell) writes: My questions for this group are: 1) What is the correct interpretation of that passage with respect to the above program? (Should it call terminate() or catch the int exception?) It should catch the int exception. 2) Is this passage ambiguous? Not in the least, AFAICT. I can't imagine why people are saying that it is. An expression which constructs a temporary hasn't been completely evaluated until that temporary has been completely constructed. Let me summarize just to make sure I understand what is going on. 1) The statement "throw Except()" does not complete because the ctor for Except() exits by throwing an exception. Thus there is no issue with an exception being thown during unwinding because the "throw Except()" statement never completes. 2) The ctor for Except throws an int exception, which should then be caught by the corresponding catch() statement. 3) The difference between this case and the footnote about an exception thrown by an exception object's copy ctor is that in the latter case the initial throw statement has completed so that the copy ctor exception does occur in the context of stack unwinding, or at least in the context of an already active exception that has not yet been handled. Is that correct? Precisely. -- Dave Abrahams Boost Consulting www.boost-consulting.com Thanks. This even makes sense to me now since there is a clear dividing line between constructing the object to be thrown, and the copying of that object by the exception mechanism. Randy. --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ] Back to top Wil Evers Guest Posted: Fri Oct 03, 2003 4:02 pm    Post subject: Re: "throw exp;" - Should terminate() be called if exp throw In article <u3cef4kke.fsf (AT) boost-consulting (DOT) com>, David Abrahams wrote: Quote: rmaddox (AT) isicns (DOT) com (Randy Maddox) writes: There is also a footnote 134 referenced at the end of the line quoted above. That footnote provides an example of an object being thrown that has a copy ctor and states that if that ctor exits by throwing an exception then terminate() is called. It seems to me that your example is quite similar in that the ctor for the object being thrown exits by throwing an exception. But it's dissimilar in that the object whose constructor throws has not been thrown yet. That's the key point. Right. So what we have is this: struct ex1 { ex1() { throw 42; } }; struct ex2 { ex2() { } ex2(const ex2&) { throw 4711; } }; void case1() { throw ex1(); // throws an int } void case2() { throw ex2(); // might result in a call to terminate() } This makes me wonder why case 2 isn't handled like case 1, which is to forget about the original exception and only report the exception escaping from the copy constructor. Calls to terminate() should be avoided unless there is no way out, and in this case, I think there is. Comments? - Wil -- Wil Evers, DOOSYS R&D BV, Utrecht, Holland [Wil underscore Evers at doosys dot com] --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ] Back to top Kevin Goodsell Guest Posted: Sat Oct 04, 2003 1:45 am    Post subject: Re: "throw exp;" - Should terminate() be called if exp throw Wil Evers wrote: Quote: Right. So what we have is this: struct ex1 { ex1() { throw 42; } }; struct ex2 { ex2() { } ex2(const ex2&) { throw 4711; } }; void case1() { throw ex1(); // throws an int } void case2() { throw ex2(); // might result in a call to terminate() } This makes me wonder why case 2 isn't handled like case 1, which is to forget about the original exception and only report the exception escaping from the copy constructor. Calls to terminate() should be avoided unless there is no way out, and in this case, I think there is. Comments? You seem to be suggesting that an exception which occurs while another exception is already "active" should take precedence. Do you really feel this is acceptable in general? My understanding is that the committee felt that there was no good solution to this problem - there's no general way to determine which (if either) exception is "more important" and should continue. Either choice loses information. -Kevin -- My email address is valid, but changes periodically. To contact me please use the address from a recent posting. --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ] Back to top        C++Talk.NET Forum Index -> C++ language, library and standards All times are GMT Goto page 1, 2  Next Page 1 of 2 Powered by phpBB © 2001, 2006 phpBB Group