Setting a New Handler

Setting a New Handler

The function std::set_new_handler() installs a function to be called when the global operator new or the global operator new[] fail. By default, operator new throws an exception of type std::bad_alloc in the event of a failure (note that Visual C++ still retains the traditional version of new, which doesn’t throw an exception in this case). set_new_handler() and its associated typedef’s are declared in the header as follows:

 typedef void (*new_handler) ();new_handler set_new_handler( new_handler new_p );

set_new_hanlder() returns the address of the current handler and installs an overriding handler.

The following program overrides the default behavior of the global operators new and new[]. Instead of throwing an std::bad_alloc exception, it invokes the user-defined function my_handler():

 #include using namespace std;class my_exception{};void my_hanlder(){  cerr << "allocation failure!" << endl; throw my_exception();}int main(){ set_new_handler(my_handler); try {  int *p = new int[2000000000]; // will probably fail   delete[] p;//we get here only if the allocation succeeded } catch (my_exception & e) { // with the exception }}
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