什么是C ++ 03宏？

Question

I'm trying to compile a library using -std=c++03 , but compilation is failing because nullptr_t is not defined.

How can I guarantee C++03 instead of C++11 compilation using a hard-coded macro?

Thanks in advance.

Answer 1

The only version detection present in the standard is the value of the macro __cplusplus : 201103 for C++11 (ISO/IEC 14882-2011 §16.8/1) and 199711 for C++98 (ISO/IEC 14882-1998 §16.8/1). C++03 didn't apparently deserve its own number and uses 199711 as well (ISO/IEC 14882-2003 §16.8/1). If this seems inadequate to you as a means of feature detection, you're not alone .

In any case, you will probably need to consult the documentation of the library in question to determine how to configure it for pre-C++11 if such is even possible.

Answer 2

Unfortunately I don't know of any macros that work for all compilers. For g++ and clang there is a macro named __GXX_EXPERIMENTAL_CXX0X__ that is only defined in c++11, so you can do

#ifndef __GXX_EXPERIMENTAL_CXX0X__
  // Do some c++03 specific code
#endif