c++ - Is it not possible to construct instances in a loop without a pointer? -


this code explode, right? loop exits, original instances die inner members if weren't pods, method do_stuff requires access members of b throw segmentation fault, correct?

void foo() {   std::vector<b> bar;   (int = 0; < 7; i++)     bar.push_back(b(i, i, i));   bar[3].do_stuff(); }

so, there way without using pointer? or have this:

void foo() {   std::vector<b*> bar;   (int = 0; < 7; i++)     bar.push_back(new b(i, i, i));   bar[3]->do_stuff();   (int = 0; < 7; i++)     delete bar[i]; }

the first code better second one.

the b instances movedsince c++11/copiedpre-c++11 vector, not fall out of scope after loop — after vector falls out of scope.

if want absolutely optimal performance, this:

void foo() {   std::vector<b> bar;   bar.reserve(7);   (int = 0; < 7; i++)     bar.emplace_back(i, i, i);   bar[3].do_stuff(); }

this guarantee 1 reallocation, , elements constructed directly inside vector (instead of moving or copying them there) per marc glisse's comments.


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