no appropriate default constructor available
in [C++]
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From: denis_browne on 17 Feb 2006 23:17 When writing the following code: class Base { Base(const Base &rhs) {} ~Base(); }; void f() { Base b; }; The compiler shouts: no appropriate default constructor available But when changing it to: void f() { Base b(); }; it compiles. Why? [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ]
From: Victor Bazarov on 18 Feb 2006 07:08 denis_browne(a)hotmail.com wrote: > When writing the following code: > > class Base > { > Base(const Base &rhs) {} > ~Base(); > }; > > void f() { > Base b; > }; > > The compiler shouts: no appropriate default constructor available Yes, since you defined the copy-c-tor, compiler does not generate the default c-tor. > But when changing it to: > > void f() { > Base b(); > }; > > it compiles. Why? Because in the latter case there is no object of type 'Base' to be constructed. V -- Please remove capital As from my address when replying by mail [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ]
From: mdlinux7 on 18 Feb 2006 07:08 > void f() { > Base b(); > } This compiles because this is treated as a function declaration bu compiler which takes void as an argument and returns a class Base object. Base b() ; // It is not a instantiation of an object via default constructor. The above code will give linking error if this function defination is not provided. Regards Dinesh denis_browne(a)hotmail.com wrote: > When writing the following code: > > class Base > { > Base(const Base &rhs) {} > ~Base(); > }; > > void f() { > Base b; > }; > > The compiler shouts: no appropriate default constructor available > > But when changing it to: > > void f() { > Base b(); > }; > > it compiles. Why? [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ]
From: Daniel T. on 18 Feb 2006 07:07 In article <1140077839.789605.237410(a)g44g2000cwa.googlegroups.com>, denis_browne(a)hotmail.com wrote: > When writing the following code: > > class Base > { > Base(const Base &rhs) {} > ~Base(); > }; > > void f() { > Base b; > }; > > The compiler shouts: no appropriate default constructor available > > But when changing it to: > > void f() { > Base b(); > }; > > it compiles. Why? In the latter case, you are declaring a function named 'b' that takes no parameters and returns a 'Base'. -- Magic depends on tradition and belief. It does not welcome observation, nor does it profit by experiment. On the other hand, science is based on experience; it is open to correction by observation and experiment. [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ]
From: Thomas Maeder on 18 Feb 2006 07:15
denis_browne(a)hotmail.com writes: > class Base > { > Base(const Base &rhs) {} > ~Base(); > }; > > void f() { > Base b; > }; > > The compiler shouts: no appropriate default constructor available > > But when changing it to: > > void f() { > Base b(); > }; > > it compiles. Why? Because Base b(); doesn't define an object, but declares a function. [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] |