[Newbie][Intrusive] - Beginners question
Hey everybody, I looked into the boost intrusive container and played around with it a bit. I tried the following code: struct animal : public boost::intrusive::list_base_hook<> { std::string name; int legs; animal(std::string n, int l) : name{std::move(n)}, legs{l} {} }; int main(int argc, char **argv) { std::vector<animal> test; boost::intrusive::list<animal> wuff; for(int n = 0; n < 5; n++) { test.push_back(animal("Katze", 4)); } for(int n = 0; n < 5; n++) { wuff.push_back(test[n]); } for(int n = 0; n < 15; n++) { wuff.push_back(test[n]); } for(auto elem : wuff) { printf("%s\n", elem.name.c_str()); } } This code does crash! I guess this is because "test" relocated the memory and therefor "wuff" lost its references. I would expect the same result if I would have a std::list with pointers to animal structures - this is why I wonder what the benefit of an intrusive container is compared to the same container with just pointers in it. Hope someone can explain me this! Thank you in advance and kind greetings Björn Als GmbH eingetragen im Handelsregister Bad Homburg v.d.H. HRB 9816, USt.ID-Nr. DE 114 165 789 Geschäftsführer: Dr. Hiroshi Nakamura, Dr. Robert Plank, Markus Bode, Heiko Lampert, Takashi Nagano, Junichi Tajika, Ergin Cansiz.
On 2020-10-21 14:33, Gaier, Bjoern via Boost-users wrote:
Hey everybody,
I looked into the boost intrusive container and played around with it a bit. I tried the following code: struct animal : public boost::intrusive::list_base_hook<> { std::string name; int legs;
animal(std::string n, int l) : name{std::move(n)}, legs{l} {} };
int main(int argc, char **argv) { std::vector<animal> test; boost::intrusive::list<animal> wuff;
for(int n = 0; n < 5; n++) { test.push_back(animal("Katze", 4)); }
for(int n = 0; n < 5; n++) { wuff.push_back(test[n]); }
because `test` has 5 elems:
for(int n = 0; n < 15; n++) <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< { wuff.push_back(test[n]); }
for(auto elem : wuff) { printf("%s\n", elem.name.c_str()); } }
This code does crash! I guess this is because "test" relocated the memory and therefor "wuff" lost its references. I would expect the same result if I would have a std::list with pointers to animal structures - this is why I wonder what the benefit of an intrusive container is compared to the same container with just pointers in it.
Hope someone can explain me this! Thank you in advance and kind greetings Björn Als GmbH eingetragen im Handelsregister Bad Homburg v.d.H. HRB 9816, USt.ID-Nr. DE 114 165 789 Geschäftsführer: Dr. Hiroshi Nakamura, Dr. Robert Plank, Markus Bode, Heiko Lampert, Takashi Nagano, Junichi Tajika, Ergin Cansiz.
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Oh gosh.... how could I oversee THAT? >o< Allright... now it works and I understand the difference.... Thank you >o< -----Original Message----- From: i.nixman@autistici.org <i.nixman@autistici.org> Sent: 21 October 2020 16:55 To: boost-users@lists.boost.org Cc: Gaier, Bjoern <Bjoern.Gaier@horiba.com> Subject: Re: [Boost-users] [Newbie][Intrusive] - Beginners question On 2020-10-21 14:33, Gaier, Bjoern via Boost-users wrote:
Hey everybody,
I looked into the boost intrusive container and played around with it a bit. I tried the following code: struct animal : public boost::intrusive::list_base_hook<> { std::string name; int legs;
animal(std::string n, int l) : name{std::move(n)}, legs{l} {} };
int main(int argc, char **argv) { std::vector<animal> test; boost::intrusive::list<animal> wuff;
for(int n = 0; n < 5; n++) { test.push_back(animal("Katze", 4)); }
for(int n = 0; n < 5; n++) { wuff.push_back(test[n]); }
because `test` has 5 elems:
for(int n = 0; n < 15; n++) <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< { wuff.push_back(test[n]); }
for(auto elem : wuff) { printf("%s\n", elem.name.c_str()); } }
This code does crash! I guess this is because "test" relocated the memory and therefor "wuff" lost its references. I would expect the same result if I would have a std::list with pointers to animal structures - this is why I wonder what the benefit of an intrusive container is compared to the same container with just pointers in it.
Hope someone can explain me this! Thank you in advance and kind greetings Björn Als GmbH eingetragen im Handelsregister Bad Homburg v.d.H. HRB 9816, USt.ID-Nr. DE 114 165 789 Geschäftsführer: Dr. Hiroshi Nakamura, Dr. Robert Plank, Markus Bode, Heiko Lampert, Takashi Nagano, Junichi Tajika, Ergin Cansiz.
_______________________________________________ Boost-users mailing list Boost-users@lists.boost.org https://lists.boost.org/mailman/listinfo.cgi/boost-users
Als GmbH eingetragen im Handelsregister Bad Homburg v.d.H. HRB 9816, USt.ID-Nr. DE 114 165 789 Geschäftsführer: Dr. Hiroshi Nakamura, Dr. Robert Plank, Markus Bode, Heiko Lampert, Takashi Nagano, Junichi Tajika, Ergin Cansiz.
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i.nixman＠autistici.org