Saturday, March 3, 2012

10 implicit translations by c++ compiler

See also posts on the "same" topic.

Note many inefficient implicit conversions are selectively, optionally "optimized away" by various compiler options. This adds even more complexity.

# proxy classes (like in [[more effC++]]) rely heavily on implicit translations
# smart pointer are drop-in replacement for raw pointers, and always relies on implicit compiler translations.
# "--any literal string--" anywhere in source code is implicitly converted to a char*const
# unnamed temporary object creation by compiler. [[more eff c++]]
# RVO
# [[c++ primer]] here are 3 identical func declarations because all array params are implicitly converted to ptr param. This is still very relevant because arrays are far more widely used than vectors (C is widespread) --
  void f(int * )
  void f(int[] )
  void f(int[5] )

#51 [[effC++]] Item 19 points out that if your Rational class overloads operator* with a Rational argument, then "aRational * 2" still works because compiler converts it first into
  aRational.operator*(2); // then it needs to convert 2 to a Rational object, so it converts the call into

  const Rational temp(2);
  aRational.operator*(temp);

#50) if f() declares a param of type Animal, you can pass in a Shape variable, if there's a converter. (See effC++ Item 26). Applies to any LHS=RHS expression like

** Type5 var2 = var3ofUnrelatedType // you get either a Type5 conversion ctor or a conversion method in UnrelatedType, 

#10) overloading the arrow operator ie "->". See P19/23 [[boost]]. IBM explains -- The statement x->f() is interpreted as (x.operator->())->f()

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