[링크] C++의 소스파일 확장자인 .cxx, .hpp, .h, .hxx 차이

출처 : http://forums.codeguru.com/showthread.php?397010-What-s-with-*.cxx-files-instead-of-*.cpp

http://kugistory.net/104

It is probably due to a project using libraries (in form of source code) that don't use the same naming convention the programmer(s) of the project.

There are at least four different extensions usable for C++ files:

• .C
  Not very popular since it requires a case-sensitive file system (otherwise, it would clash with old .c file names), and even a few modern OS are not case-sensitive.
• .c++
  Some OS or file systems don't support the + character in file names.
• .cpp
  That's very portable across file systems.
  But, it might be less consistent than .cxx
• .cxx
  Very portable across file systems (not more than .cpp)
  Using the name CXX for C++ is quite popular because CPP usually designates the C (and C++) pre-processor.
  For example, these environment variables/makefile macros
  
  • CPPFLAGS
    Represents the flags passed to the pre-processor.
  • CFLAGS
    Flags passed to the C compiler.
  • CXXFLAGS
    Flags passed to the C++ compiler.
  • LDFLAGS
    Flags passed to the linker.
  • CC
    The path to the C compiler.
  • CPP
    The path to the pre-processor.
  • CXX
    The path to the C++ compiler.
  • LD
    The path to the linker.
  
  That's why, with the above notations, it's very natural to give the .cxx extension to C++ files.

For headers, there are at least five extensions:

• .h
  Traditional C header files.
  Since the compiler doesn't do anything based on this extension, it can be used for C++ header files too.
  Furthermore, there are a lot of header files that are designed to be included by both C and C++ translation units.
  In that case, it's natural to give them this extension.
• .H, .hpp or .hxx
  That's very natural to give one of these extensions for C++ header files (being consistent with the name of C++ translation units).
  That's not a bad idea to use one of these name for pure C++ header files only (containing class definitions, or templates, or any other feature not supported by C).
• No extension
  That's internally used by a number of C++ compilers for iostream, vector, algorithm and all others new-style C++ headers.

There are probably other (less popular) extensions for headers.
Perhaps .cpp and .i