C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  run time error          C++Talk.NET Forum Index -> C++ language (comp.lang.c++) View previous topic :: View next topic   Author Message Gary Wessle Guest Posted: Sun Dec 24, 2006 9:13 am    Post subject: run time error Hi I am getting the following output then trying to run the code below. string does not like what I am doing, why and whats the fix? thanks Program received signal SIGSEGV, Segmentation fault. 0x4e34ad7f in std::string::append () from /usr/lib/libstdc++.so.6 #include <string> #include <iostream> using namespace std; class Typ{ public: string nam; Typ():nam("mary"){} }; int main (){ Typ* typ; string a = "jack"; string f = a.substr(0,1) + "/" + typ->nam; cout << f << endl; } Back to top p-Brane Guest Posted: Sun Dec 24, 2006 9:30 am    Post subject: Re: run time error "Gary Wessle" <phddas (AT) yahoo (DOT) com> wrote in message news:m3irg2gf53.fsf (AT) localhost (DOT) localdomain... Quote: Hi I am getting the following output then trying to run the code below. string does not like what I am doing, why and whats the fix? thanks Program received signal SIGSEGV, Segmentation fault. 0x4e34ad7f in std::string::append () from /usr/lib/libstdc++.so.6 #include <string #include <iostream using namespace std; class Typ{ public: string nam; Typ():nam("mary"){} }; int main (){ Typ* typ; string a = "jack"; string f = a.substr(0,1) + "/" + typ->nam; cout << f << endl; } typ is uninitialized. Try this... Typ* typ = new Typ; Back to top Salt_Peter Guest Posted: Sun Dec 24, 2006 10:07 am    Post subject: Re: run time error Gary Wessle wrote: Quote: Hi I am getting the following output then trying to run the code below. string does not like what I am doing, why and whats the fix? thanks Program received signal SIGSEGV, Segmentation fault. 0x4e34ad7f in std::string::append () from /usr/lib/libstdc++.so.6 #include <string #include <iostream using namespace std; class Typ{ public: string nam; Typ():nam("mary"){} }; int main (){ Typ* typ; typ is not an instance. Its just a dumb pointer. Until proven otherwise, a pointer holds an address to nothing. Here is a suggestion: when you declare a pointer, always initialize it. Typ* typ = 0; // black hole That way you won't forget that its a pointer to nothing until its given a valid address. Quote: string a = "jack"; string f = a.substr(0,1) + "/" + typ->nam; cout << f << endl; } My fav analogy: If you mail an envelope to a fictitiuos address (a pointer) half-way around the world, a postman will not construct a house just to receive the envelope. Back to top BobR Guest Posted: Sun Dec 24, 2006 10:10 am    Post subject: Re: run time error Gary Wessle wrote in message ... Quote: Hi I am getting the following output then trying to run the code below. string does not like what I am doing, why and whats the fix? thanks Program received signal SIGSEGV, Segmentation fault. 0x4e34ad7f in std::string::append () from /usr/lib/libstdc++.so.6 #include <string #include <iostream using namespace std; class Typ{ public: string nam; Typ() : nam( "mary" ){} }; int main (){ // > Typ* typ; // <-- you forgot to initialise this!! Typ typ; Quote: string a = "jack"; // > string f = a.substr(0,1) + "/" + typ->nam; string f = a.substr(0,1) + "/" + typ.nam; Quote: cout << f << endl; } // out: j/mary // or int main (){ Typ typ1; Typ *typ( &typ1 ); string a( "jack" ); string f = a.substr(0,1) + "/" + typ->nam; cout << f << endl; } // out: j/mary Or, what p-Brane showed you, but wirh a 'delete'! -- Bob R POVrookie Back to top Gianni Mariani Guest Posted: Sun Dec 24, 2006 10:10 am    Post subject: Re: run time error Salt_Peter wrote: .... Quote: My fav analogy: If you mail an envelope to a fictitiuos address (a pointer) half-way around the world, a postman will not construct a house just to receive the envelope. Totally off-topic. Funny you should say that, but there is use for a smart pointer type that does exactly that - i.e. new on dereference. Back to top Salt_Peter Guest Posted: Sun Dec 24, 2006 10:10 am    Post subject: Re: run time error Gianni Mariani wrote: Quote: Salt_Peter wrote: ... My fav analogy: If you mail an envelope to a fictitiuos address (a pointer) half-way around the world, a postman will not construct a house just to receive the envelope. Totally off-topic. Funny you should say that, but there is use for a smart pointer type that does exactly that - i.e. new on dereference. a PO box? While you are on the subject of smart pointers... It might be of interest for the OP that most smart pointers are default initialized to nullptr. These will also usually put out an assertion if accessed before being properly initialized. #include <iostream> #include <ostream> #include <boost/shared_ptr.hpp> template< typename S > class MyType { S s; public: MyType() : s() { } MyType(const S& r_s) : s(r_s) { } const S& get() const { return s; } }; int main() { typedef MyType< std::string > MyString; typedef boost::shared_ptr< MyString > SPtrStr; SPtrStr sp_s( new MyString("string 0") ); std::cout << sp_s->get() << std::endl; // ok SPtrStr sp_test; std::cout << sp_test->get() << std::endl; // assertion } /* string 0 ....Assertion `px != 0' failed. ....Aborted */ Back to top Xian Guest Posted: Mon Dec 25, 2006 4:05 am    Post subject: Re: run time error p-Brane wrote: Quote: "Gary Wessle" <phddas (AT) yahoo (DOT) com> wrote in message news:m3irg2gf53.fsf (AT) localhost (DOT) localdomain... Hi I am getting the following output then trying to run the code below. string does not like what I am doing, why and whats the fix? thanks Program received signal SIGSEGV, Segmentation fault. 0x4e34ad7f in std::string::append () from /usr/lib/libstdc++.so.6 #include <string #include <iostream using namespace std; class Typ{ public: string nam; Typ():nam("mary"){} }; int main (){ Typ* typ; string a = "jack"; string f = a.substr(0,1) + "/" + typ->nam; cout << f << endl; } typ is uninitialized. Try this... Typ* typ = new Typ; Remember that if you create a new object you should delete it after you've finished with it. delete typ; Also if you don't want to create a new object when you declare a pointer, you can set it to NULL, because dereferenceing a null pointer is safe, it just breaks you program. Whereas dereferencing an arbitrary pointer has unpredictable results (sometimes worse than a SIGSEGV). -- /Xian 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.