Default value of dynamic bool array in C++ -

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• does new[] call default constructor in c++? 3 answers

i need create bool array unknown length passed parameter. so, have following code:

void foo (int size) {      bool *boolarray = new bool[size];      (int = 0; < size; i++) {              if (!boolarray[i]) {                  cout << boolarray[i];              }     } } 

i thought boolean array initializing false values...

then, if run code in eclipse (on ubuntu), works fine me, function prints values because !boolarray[i] return true (but values not false values, garbage values). if run in visual studio, values garbage values too, function not print value (because !boolarray[i] returns false). why array values not false values default?!? , why !boolarray[i] returns false in visual studio returns true in eclipse?!?

i read question: set default value of dynamic array, if change code following, works fine me (in eclipse , in visual studio)! have no idea why.

void foo (int size) {      bool *boolarray = new bool[size]();      (int = 0; < size; i++) {              if (!boolarray[i]) {                  cout << boolarray[i];              }           } } 

sorry bad english!

thanks in advance!

adding () pod instantiation, invokes value initialization in c++03 , later. in c++98 invoked default initialization. both reduce zero initialization pod types, , booleans 0 false.

e.g., if s pod struct, , have variable

s o; 

then can 0 doing

o = s(); 

no need unsafe , ugly memset.

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by way, std::vector<bool> higher level alternative raw array of bool, due what's seen premature optimization has bit odd behavior: supports implementation each boolean value represented single bit, , dereferencing iterator doesn't give reference bool 1 might expect general std::vector. better alternative e.g. std::vector<my_bool_enum>, my_bool_enum defined. or std::vector<char>. ;-)

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regarding

“and why !boolarray[i] returns false in visual studio returns true in eclipse?!?”

it's visual c++ chooses efficiency, not initializing doesn't have to, while compiler used in eclipse (presumably g++) initialize though doesn't have , isn't requested do.

i prefer visual c++ behavior here 2 reasons:

• a main idea in c++ you don't pay don't use, , visual c++ behavior here in line idea.

• zero-initialization can give users false impression code works, when in fact it's not portable.