As we all know that there is a this pointer for all objects, but if we want to use smart pointer, how to we use.

It turns out that it's not that easy by creating a share_ptr from this pointer, since we may have many shared_ptrs points to the same object with without knowing each other.

Taking this code as an example, if we create a share_ptr by dangerous function, we will have two share_ptrs pointing to the same object. Both sp1 and sp2 point to same object, and when the two exits it leads problem.

struct S
{
  shared_ptr<S> dangerous() {
    return shared_ptr<S>(this);  // don't do this!
  }
};

int main() {
  shared_ptr<S> sp1(new S);
  shared_ptr<S> sp2 = sp->dangerous();
  return 0;
}

How to fix this problem, use the std::enable_shared_from_this help class defined in, it is introduced in C++11.

struct S: enable_shared_from_this<S> {
  shared_ptr<S> dangerous() {
    return shared_from_this();
  }
};

int main() {
  shared_ptr<S> sp1(new S);
  shared_ptr<S> sp2 = sp->dangerous();  // not dangerous

  return 0;
}

#cpp #share_ptr

As a C++ programmer for many years, I never noticed the other style of logic operators in C++ until today.

When I review part of code witten by one of my colleague which is a mainly a Java programmer, and find he uses and other than && in if statement.

And I check cppreference, and find the C++ operator alternative.

Primary	Alternative
&&	and
&=	and_eq
&	bitand
|	bitor
~	compl
!	not
!=	not_eq
||	or
|=	or_eq
^	xor
^=	xor_eq
{	<%
}	%>
[	<:
]	:>
#	%:
##	%:%:

The reason for alternative operators is that the source code maybe not in ASCII set, and don't have the proper operators.

#cpp #programming #operator