CODEWITHSUNDEEP
c++static
keety
keety

Reputation: 17441

Function Scoped Static Non Pod Object Initialization

I was under the impression that Function Scoped Non-Pod structures are intialized the first time the function is invoked. However on VS-2010 it appears if the constructor throws an exception the constructor is invoked each time until a successful construction.

Is this behavior implementation specific or something the standard guarantees ?

Below is contrived example to demonstrate the behaviour :

#include <iostream>
#include <string>
using namespace std;

//dummy resource class
class Resource {
 public:
 Resource() {
   cerr<<"Allocate Resource "<<endl;
 }

~Resource() {
   cerr<<"Free Resource"<<endl;
 }
};

//dummy class which will be statically instantiated
class Dummy {
  public:

 Dummy()  {
   cerr<<"in Dummy"<<endl;
   throw(string("error"));
  }

  Resource res;

};

//main program
int main()  {

 for(int i = 0;i<3;i++) {
   try {
     //create a static object  throw and exception
     static Dummy foo;
   }
   catch ( std::string &e) {
     cerr<<"Caught exception:"<<e<<endl<<endl;
   }   
 }
 return 1;
}

Output:

Iteration:0

Allocate Resource

Static Object Constructor

Free Resource

Caught exception:error

Iteration:1

Allocate Resource

Static Object Constructor

Free Resource

Caught exception:error

Iteration:2

Allocate Resource

Static Object Constructor

Free Resource

Caught exception:error**

Upvotes: 0

Views: 180

Answers (1)

ildjarn
ildjarn

Reputation: 62975

I was under the impression that Function Scoped Non-Pod structures are intialized the first time the function is invoked.

Sure, but think about what 'initialized' means – if the constructor throws, the object is not initialized because there is no object. Consequently, the next time the object declaration is encountered, it will (attempt to) be initialized again.

Upvotes: 4

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