Reason for C++ member function hiding [duplicate]

by

Name lookup works by looking in the current scope for matching names, if nothing is found then it looks in the enclosing scope, if nothing is found it looks in the enclosing scope, etc. until reaching the global namespace.

This isn’t specific to classes, you get exactly the same name hiding here:

#include <iostream>

namespace outer
{
  void foo(char c) { std::cout << "outer\n"; }

  namespace inner
  {
    void foo(int i) { std::cout << "inner\n"; }

    void bar() { foo('c'); }
  }
}

int main()
{
  outer::inner::bar();
}

Although outer::foo(char) is a better match for the call foo('c') name lookup stops after finding outer::inner::foo(int) (i.e. outer::foo(char) is hidden) and so the program prints inner.

If member function name weren’t hidden that would mean name lookup in class scope behaved differently to non-class scope, which would be inconsistent and confusing, and make C++ even harder to learn.

So there’s no technical reason the name lookup rules couldn’t be changed, but they’d have to be changed for member functions and other types of name lookup, it would make compilers slower because they’d have to continue searching for names even after finding matching names in the current scope. Sensibly, if there’s a name in the current scope it’s probably the one you wanted. A call in a scope A probably wants to find names in that scope, e.g. if two functions are in the same namespace they’re probably related (part of the same module or library) and so if one uses the name of the other it probably means to call the one in the same scope. If that’s not what you want then use explicit qualification or a using declaration to tell the compiler the other name should be visible in that scope.

More Related Contents:

  1. How to find out how many bits are set (equal 1) in the product of two integers [closed]
  2. Why does dividing two int not yield the right value when assigned to double?
  3. How does guaranteed copy elision work?
  4. How do I see a C/C++ source file after preprocessing in Visual Studio?
  5. Image Processing: Algorithm Improvement for ‘Coca-Cola Can’ Recognition
  6. Where exactly does C++ standard say dereferencing an uninitialized pointer is undefined behavior?
  7. Serializing a class which contains a std::string
  8. What does OpenCV’s cvWaitKey( ) function do?
  9. static_assert dependent on non-type template parameter (different behavior on gcc and clang)
  10. Division in C++ not working as expected
  11. Good input validation loop using cin – C++
  12. C++ high precision time measurement in Windows
  13. Windows 7 timing functions – How to use GetSystemTimeAdjustment correctly?
  14. Why should I avoid std::enable_if in function signatures
  15. Is there a function to copy an array in C/C++?
  16. get absolute value without using abs function nor if statement
  17. C++ polymorphism without pointers
  18. Preventing a MEX file from crashing in MATLAB
  19. Can we use a user defined class for the key in a STL map?
  20. Is there any case where a return of a RValue Reference (&&) is useful?
  21. C++ : Creating an array with a size entered by the user
  22. Who defines C operator precedence and associativity?
  23. What is Linux’s native GUI API?
  24. Align cout format as table’s columns
  25. pair pair as key of unordered_map issue
  26. Convert Lat/Longs to X/Y Co-ordinates
  27. C++ Class wrapper around fundamental types
  28. Dependent name resolution & namespace std / Standard Library
  29. GCC std::thread not found in namespace std
  30. c++ global object

Leave a Comment