Question

I am using bcc32 command line compiler from Borland Embarcadero. Consider this program:

    int main(int, char **)
    {
        try
        {
            std::string *a = new string(0xf0000000, ' ');
            ...
            delete a;
        }
        catch(const std::bad_alloc &)
        {
            ...
        }
    }

When the std::string constructor throws a memory exception, the stack is unwound and control is passed to the catch-block. Gnu compilers build in code to delete the memory allocated for the std::string object ‘auto-magically’, as was stated by someone who commented on the answer in Who deletes the memory allocated during a "new" operation which has exception in constructor? which I wrote. I ran the program in http://ideone.com/IRxHX and the result is that nobody frees the memory allocated by ‘operator new’ if an exception is thrown before the result of ‘new’ is stored in an lvalue. In the above case the variable ‘a’.

Questions are:
1 Is there a way to delete the memory generated by ‘new’ in case of an exception, as a part of the stack unwind procedure?
2 What does the C++ standard demand from compilers in this case

Answer 1

Either your compiler is broken, or something else funny is going on. The implementation is required to free the memory:

5.3.4/17:

If any part of the object initialization described above terminates by
throwing an exception and a suitable deallocation function can be
found, the deallocation function is called to free the memory in which
the object was being constructed, after which the exception continues
to propagate in the context of the new- expression. If no unambiguous
matching deallocation function can be found, propagating the exception
does not cause the object’s memory to be freed.