How to Determine the Default C Standard Used by g ?

C Standard Detection in g

In C , the standard compiler version may affect the behavior and compatibility of your code. When compiling with g , understanding the default standard is crucial.

Consider the following code snippet:

#include <fstream>
#include <string>

int main() {
    std::string filename = "input.txt";
    std::ifstream in(filename);

    return 0;
}

If you compile this code on Windows using the g example.cpp command, it may fail due to linker errors related to converting from std::string to const char*. However, specifying a specific C standard using g -std=c 17 example.cpp resolves this issue.

To determine the default C standard used by g , you can execute the following command:

g++ -dM -E -x c++ /dev/null | grep -F __cplusplus

For example, using this command on the Ubuntu 4.8.4 version of g , you would get the output:

#define __cplusplus 199711L

This indicates that the default C standard for this version of g is C 98 (199711L represents the November 1997 revision of the C standard).

It is recommended to always specify the desired C standard explicitly when compiling with g . This ensures that the code conforms to the intended standard and avoids potential compatibility issues that may arise from using an outdated or undesired standard.

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