CODEWITHSUNDEEP
c++gcc
ArtificiallyIntelligent
ArtificiallyIntelligent

Reputation: 977

How to tell default c++ version (without explicit flag) for my compiler?

I am using gcc (GCC) 4.4.7 20120313 (Red Hat 4.4.7-4)

Where to look for it? I know how to add flags to force a particular standard with GNU extension.

Upvotes: 0

Views: 699

Answers (3)

ecatmur
ecatmur

Reputation: 157484

You can use the predefined macro __cplusplus:

$ echo __cplusplus | g++ -E -x c++ -c -
# 1 "<stdin>"
# 1 "<built-in>"
# 1 "<command-line>"
# 1 "<stdin>"
199711L

Explanation of command line arguments:

  • -E - only run preprocessor
  • -x c++ - input file is a C++ source file (necessary for __cplusplus to be defined)
  • -c - - read from stdin

Alternatively, the -dM option will dump all predefined macros:

$ g++ -dM -E -x c++ /dev/null | grep __cplusplus
#define __cplusplus 199711L

Upvotes: 1

Josh Kelley
Josh Kelley

Reputation: 58442

Like Jesper Juhl said, checking the docs is probably best.

If you want, though, you can also ask your compiler.

#include <iostream>

using namespace std;

int main(int, char**) {
  cout << __cplusplus << endl;
  return 0;
}

From the GCC docs on predefined macros, this will output one of the following:

199711L for the 1998 C++ standard, 201103L for the 2011 C++ standard, 201402L for the 2014 C++ standard, or an unspecified value strictly larger than 201402L for the experimental languages enabled by -std=c++1z and -std=gnu++1z.

Upvotes: 3

Jesper Juhl
Jesper Juhl

Reputation: 31478

Have you tried reading the documentation? man g++ is one place to start... But, to answer the question; that gcc version compiles as C++98 by default (actually, the GNU variant).

If you want to detect the C++version in use without reading documentation or without specifying -std=, then you could just try compiling some code using only C++98, some using C++03 features, C++11 features and C++14 features and see which one(s) it accept. But just reading the docs is easier.

Upvotes: 1

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