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* [Bug c++/12277] Warn on dynamic casts with known NULL results. [not found] <bug-12277-3548@http.gcc.gnu.org/bugzilla/> @ 2005-11-26 8:05 ` gdr at gcc dot gnu dot org 2007-06-11 11:19 ` pinskia at gcc dot gnu dot org ` (2 subsequent siblings) 3 siblings, 0 replies; 12+ messages in thread From: gdr at gcc dot gnu dot org @ 2005-11-26 8:05 UTC (permalink / raw) To: gcc-bugs -- gdr at gcc dot gnu dot org changed: What |Removed |Added ---------------------------------------------------------------------------- AssignedTo|unassigned at gcc dot gnu |gdr at gcc dot gnu dot org |dot org | Status|NEW |ASSIGNED Last reconfirmed|2005-09-10 19:11:30 |2005-11-26 08:05:53 date| | http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12277 ^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug c++/12277] Warn on dynamic casts with known NULL results. [not found] <bug-12277-3548@http.gcc.gnu.org/bugzilla/> 2005-11-26 8:05 ` [Bug c++/12277] Warn on dynamic casts with known NULL results gdr at gcc dot gnu dot org @ 2007-06-11 11:19 ` pinskia at gcc dot gnu dot org 2009-07-06 20:45 ` jason at gcc dot gnu dot org 2009-07-06 20:56 ` bangerth at gmail dot com 3 siblings, 0 replies; 12+ messages in thread From: pinskia at gcc dot gnu dot org @ 2007-06-11 11:19 UTC (permalink / raw) To: gcc-bugs ------- Comment #4 from pinskia at gcc dot gnu dot org 2007-06-11 11:18 ------- *** Bug 32282 has been marked as a duplicate of this bug. *** -- pinskia at gcc dot gnu dot org changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |Woebbeking at web dot de http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12277 ^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug c++/12277] Warn on dynamic casts with known NULL results. [not found] <bug-12277-3548@http.gcc.gnu.org/bugzilla/> 2005-11-26 8:05 ` [Bug c++/12277] Warn on dynamic casts with known NULL results gdr at gcc dot gnu dot org 2007-06-11 11:19 ` pinskia at gcc dot gnu dot org @ 2009-07-06 20:45 ` jason at gcc dot gnu dot org 2009-07-06 20:56 ` bangerth at gmail dot com 3 siblings, 0 replies; 12+ messages in thread From: jason at gcc dot gnu dot org @ 2009-07-06 20:45 UTC (permalink / raw) To: gcc-bugs ------- Comment #5 from jason at gcc dot gnu dot org 2009-07-06 20:45 ------- This is only known to be NULL if we know the dynamic type of p. Consider: struct Foo: Base {}; struct Bar: Derived, Foo {}; Bar bar; Base *p2 = (Foo*)&bar; A dynamic_cast to Derived from p2 should succeed. But it still seems reasonable to give a warning for pinskia's testcase. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12277 ^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug c++/12277] Warn on dynamic casts with known NULL results. [not found] <bug-12277-3548@http.gcc.gnu.org/bugzilla/> ` (2 preceding siblings ...) 2009-07-06 20:45 ` jason at gcc dot gnu dot org @ 2009-07-06 20:56 ` bangerth at gmail dot com 3 siblings, 0 replies; 12+ messages in thread From: bangerth at gmail dot com @ 2009-07-06 20:56 UTC (permalink / raw) To: gcc-bugs ------- Comment #6 from bangerth at gmail dot com 2009-07-06 20:56 ------- (In reply to comment #3) I had to stare at the testcase in comment #3 for a little while and thought others may have to as well: it fails because the inheritance from Base is *private*, not because the dynamically created object is not derived a Derived object at all. W. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12277 ^ permalink raw reply [flat|nested] 12+ messages in thread
[parent not found: <bug-12277-4@http.gcc.gnu.org/bugzilla/>]
* [Bug c++/12277] Warn on dynamic casts with known NULL results. [not found] <bug-12277-4@http.gcc.gnu.org/bugzilla/> @ 2013-11-07 10:26 ` paolo.carlini at oracle dot com 2014-11-27 21:21 ` gcc at dixie dot net.nz ` (2 subsequent siblings) 3 siblings, 0 replies; 12+ messages in thread From: paolo.carlini at oracle dot com @ 2013-11-07 10:26 UTC (permalink / raw) To: gcc-bugs http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12277 Paolo Carlini <paolo.carlini at oracle dot com> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|ASSIGNED |NEW ^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug c++/12277] Warn on dynamic casts with known NULL results. [not found] <bug-12277-4@http.gcc.gnu.org/bugzilla/> 2013-11-07 10:26 ` paolo.carlini at oracle dot com @ 2014-11-27 21:21 ` gcc at dixie dot net.nz 2014-11-27 21:23 ` gcc at dixie dot net.nz 2014-11-28 8:44 ` ville.voutilainen at gmail dot com 3 siblings, 0 replies; 12+ messages in thread From: gcc at dixie dot net.nz @ 2014-11-27 21:21 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=12277 Andrew Dixie <gcc at dixie dot net.nz> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |gcc at dixie dot net.nz --- Comment #7 from Andrew Dixie <gcc at dixie dot net.nz> --- With final, I believe the following dynamic_cast must always return NULL: struct a1 { virtual ~a1() {} }; struct a2 final { virtual ~a2() {} }; bool test(a1 *x) { return dynamic_cast<a2 *>(x) != 0; } ^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug c++/12277] Warn on dynamic casts with known NULL results. [not found] <bug-12277-4@http.gcc.gnu.org/bugzilla/> 2013-11-07 10:26 ` paolo.carlini at oracle dot com 2014-11-27 21:21 ` gcc at dixie dot net.nz @ 2014-11-27 21:23 ` gcc at dixie dot net.nz 2014-11-28 8:44 ` ville.voutilainen at gmail dot com 3 siblings, 0 replies; 12+ messages in thread From: gcc at dixie dot net.nz @ 2014-11-27 21:23 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=12277 --- Comment #8 from Andrew Dixie <gcc at dixie dot net.nz> --- Created attachment 34130 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=34130&action=edit dynamic_cast warning ^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug c++/12277] Warn on dynamic casts with known NULL results. [not found] <bug-12277-4@http.gcc.gnu.org/bugzilla/> ` (2 preceding siblings ...) 2014-11-27 21:23 ` gcc at dixie dot net.nz @ 2014-11-28 8:44 ` ville.voutilainen at gmail dot com 3 siblings, 0 replies; 12+ messages in thread From: ville.voutilainen at gmail dot com @ 2014-11-28 8:44 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=12277 Ville Voutilainen <ville.voutilainen at gmail dot com> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |ville.voutilainen at gmail dot com --- Comment #9 from Ville Voutilainen <ville.voutilainen at gmail dot com> --- (In reply to Andrew Dixie from comment #7) > With final, I believe the following dynamic_cast must always return NULL: > > struct a1 { virtual ~a1() {} }; > struct a2 final { virtual ~a2() {} }; > > bool test(a1 *x) > { > return dynamic_cast<a2 *>(x) != 0; > } If a1 is final, sure. Whether a2 is final is irrelevant. ^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug c++/12277] New: Warn on dynamic casts with known NULL results. @ 2003-09-14 16:55 tilps at hotmail dot com 2003-09-14 17:23 ` [Bug c++/12277] " pinskia at gcc dot gnu dot org ` (3 more replies) 0 siblings, 4 replies; 12+ messages in thread From: tilps at hotmail dot com @ 2003-09-14 16:55 UTC (permalink / raw) To: gcc-bugs PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org. http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12277 Summary: Warn on dynamic casts with known NULL results. Product: gcc Version: 3.4 Status: UNCONFIRMED Severity: enhancement Priority: P2 Component: c++ AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: tilps at hotmail dot com CC: gcc-bugs at gcc dot gnu dot org While this can not be done generally - if the inheritence relation between the type being cast from and the type being cast to is known at the time of use, there are some cases where a dynamic cast can be sure to return NULL. I can not think of any valid use of a dynamic cast which will always return NULL - so therefore I suggest that a warning be given. The specific case which bothered me (and hence why i'm writing this) is upcasting through private inheritence always gives NULL for dynamic cast. ^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug c++/12277] Warn on dynamic casts with known NULL results. 2003-09-14 16:55 [Bug c++/12277] New: " tilps at hotmail dot com @ 2003-09-14 17:23 ` pinskia at gcc dot gnu dot org 2003-09-15 0:42 ` bangerth at dealii dot org ` (2 subsequent siblings) 3 siblings, 0 replies; 12+ messages in thread From: pinskia at gcc dot gnu dot org @ 2003-09-14 17:23 UTC (permalink / raw) To: gcc-bugs PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org. http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12277 pinskia at gcc dot gnu dot org changed: What |Removed |Added ---------------------------------------------------------------------------- Keywords| |diagnostic ^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug c++/12277] Warn on dynamic casts with known NULL results. 2003-09-14 16:55 [Bug c++/12277] New: " tilps at hotmail dot com 2003-09-14 17:23 ` [Bug c++/12277] " pinskia at gcc dot gnu dot org @ 2003-09-15 0:42 ` bangerth at dealii dot org 2004-05-20 12:12 ` pinskia at gcc dot gnu dot org 2004-05-20 13:25 ` pinskia at gcc dot gnu dot org 3 siblings, 0 replies; 12+ messages in thread From: bangerth at dealii dot org @ 2003-09-15 0:42 UTC (permalink / raw) To: gcc-bugs PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org. http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12277 bangerth at dealii dot org changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |NEW Ever Confirmed| |1 Last reconfirmed|0000-00-00 00:00:00 |2003-09-15 00:15:55 date| | ------- Additional Comments From bangerth at dealii dot org 2003-09-15 00:15 ------- Seems reasonable. W. ^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug c++/12277] Warn on dynamic casts with known NULL results. 2003-09-14 16:55 [Bug c++/12277] New: " tilps at hotmail dot com 2003-09-14 17:23 ` [Bug c++/12277] " pinskia at gcc dot gnu dot org 2003-09-15 0:42 ` bangerth at dealii dot org @ 2004-05-20 12:12 ` pinskia at gcc dot gnu dot org 2004-05-20 13:25 ` pinskia at gcc dot gnu dot org 3 siblings, 0 replies; 12+ messages in thread From: pinskia at gcc dot gnu dot org @ 2004-05-20 12:12 UTC (permalink / raw) To: gcc-bugs ------- Additional Comments From pinskia at gcc dot gnu dot org 2004-05-19 13:30 ------- *** Bug 15541 has been marked as a duplicate of this bug. *** -- What |Removed |Added ---------------------------------------------------------------------------- CC| |bangerth at dealii dot org http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12277 ^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug c++/12277] Warn on dynamic casts with known NULL results. 2003-09-14 16:55 [Bug c++/12277] New: " tilps at hotmail dot com ` (2 preceding siblings ...) 2004-05-20 12:12 ` pinskia at gcc dot gnu dot org @ 2004-05-20 13:25 ` pinskia at gcc dot gnu dot org 3 siblings, 0 replies; 12+ messages in thread From: pinskia at gcc dot gnu dot org @ 2004-05-20 13:25 UTC (permalink / raw) To: gcc-bugs ------- Additional Comments From pinskia at gcc dot gnu dot org 2004-05-19 13:31 ------- And here is an example: struct Base { virtual ~Base () {} }; class Derived : Base { friend int main (); }; #include <cassert> int main () { Base * p = new Derived; assert(dynamic_cast<Derived *>(p)); // fails } -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12277 ^ permalink raw reply [flat|nested] 12+ messages in thread
end of thread, other threads:[~2014-11-28 8:44 UTC | newest] Thread overview: 12+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- [not found] <bug-12277-3548@http.gcc.gnu.org/bugzilla/> 2005-11-26 8:05 ` [Bug c++/12277] Warn on dynamic casts with known NULL results gdr at gcc dot gnu dot org 2007-06-11 11:19 ` pinskia at gcc dot gnu dot org 2009-07-06 20:45 ` jason at gcc dot gnu dot org 2009-07-06 20:56 ` bangerth at gmail dot com [not found] <bug-12277-4@http.gcc.gnu.org/bugzilla/> 2013-11-07 10:26 ` paolo.carlini at oracle dot com 2014-11-27 21:21 ` gcc at dixie dot net.nz 2014-11-27 21:23 ` gcc at dixie dot net.nz 2014-11-28 8:44 ` ville.voutilainen at gmail dot com 2003-09-14 16:55 [Bug c++/12277] New: " tilps at hotmail dot com 2003-09-14 17:23 ` [Bug c++/12277] " pinskia at gcc dot gnu dot org 2003-09-15 0:42 ` bangerth at dealii dot org 2004-05-20 12:12 ` pinskia at gcc dot gnu dot org 2004-05-20 13:25 ` pinskia at gcc dot gnu dot org
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