CPP 1.3 MAILINGLIST Avatar
  1. OMG Issue

CPP13 — fixed-length _var assignment from pointer

  • Key: CPP13-29
  • Legacy Issue Number: 3247
  • Status: open  
  • Source: Triodia Technologies Pty Ltd ( Michi Henning)
  • Summary:

    the new mapping for _var types for fixed-length underlying types shows:

    T_var &operator=(T *t) {
    if (t != m_ptr)

    { delete m_ptr; m_ptr = t; }

    return *this;
    }

    This guards against self assignment when a pointer is assigned to the _var.

    I don't think this is right:

    • Assigning a pointer to a _var that already owns what the pointer
      points at is almost certainly an error:

    MyStruct * p = ...;
    MyStruct_var v = p; // OK

    // ...

    v = p; // Almost certainly an error

    • We don't do the same thing elsewhere. On page 1-13:

    A_var &operator=(const A_var& a)

    { reset(p); return *this; }

    This is inconsistent: assignment of a _ptr to a _var reference
    is not safe against self assignment, so assignment of a pointer
    to the _var for a fixed-length type shouldn't be either.

    Note that the other assignment operators are just fine – I'm only objecting
    to testing for self-assignment for operator= with a pointer as the RHS.
    (A nice compiler could even insert an assertions if a _var is assigned the
    same thing that it already points at.)

  • Reported: CPP 1.1 — Tue, 25 Jan 2000 05:00 GMT
  • Updated: Fri, 6 Mar 2015 20:57 GMT