Function already defined error in C++

by

By default, these functions have external linkage. That means each translation unit has functions called double round(double r) and float round(float r), which causes a name collision at link time.

Some possible solutions are:

  1. Declare the functions as static, which implies internal linkage
  2. Inline the functions
  3. Move the implementation out of the header and into a c/c++ file

Read more here:
What is external linkage and internal linkage?

By the way, include guards protect a single translation unit from including a header file multiple times. That’s a different issue that what you’re seeing here.

More Related Contents:

  1. Difference between using std::vector and include<vector>
  2. Using includes with c++ shared libraries
  3. C++ #include guards
  4. What is an undefined reference/unresolved external symbol error and how do I fix it?
  5. Detecting superfluous #includes in C/C++?
  6. Eclipse CDT: Symbol ‘cout’ could not be resolved
  7. Include header files using command line option?
  8. How should I detect unnecessary #include files in a large C++ project?
  9. Undefined symbols “vtable for …” and “typeinfo for…”?
  10. Should I include or in C++ programs?
  11. Is it a good idea to wrap an #include in a namespace block?
  12. C++ Header order [closed]
  13. undefined reference to `__gxx_personality_sj0`
  14. How to tell where a header file is included from?
  15. Circular C++ Header Includes
  16. Unresolved external symbol LNK2019
  17. Multiple definition of inline functions when linking static libs
  18. How to define several include path in Makefile
  19. When can you omit the file extension in an #include directive?
  20. Difference between using #include and #include in C++
  21. When is #include library required in C++?
  22. Include all files in a directory?
  23. Using pthread in c++
  24. Is the backslash acceptable in C and C++ #include directives?
  25. How does #include work in C++?
  26. cmath vs math.h (And similar c-prefixed vs .h extension headers)
  27. Referencing memory operands in .intel_syntax GNU C inline assembly
  28. #include absolute path syntax in c/c++
  29. Do you know tool building tree of include files in project\file?
  30. compiler cannot recognize my class in c++ – cyclic dependency

Leave a Comment