__STDC_VERSION__ macro not always defined

[ilanbiala]

I'm trying to use this library in a project with g++, and it seems that __STDC_VERSION__ is not defined when compiling C++ (https://gcc.gnu.org/onlinedocs/cpp/Standard-Predefined-Macros.html). This seems like it poses an issue where:

1. https://github.com/j123b567/scpi-parser/blob/master/libscpi/inc/scpi/cc.h#L44-L55 does not define C99
2. https://github.com/j123b567/scpi-parser/blob/master/libscpi/inc/scpi/cc.h#L107-L109 then does not define HAVE_STDBOOL
3. https://github.com/j123b567/scpi-parser/blob/master/libscpi/inc/scpi/cc.h#L161-L163 then defines HAVE_STDBOOL to be 0
4. https://github.com/j123b567/scpi-parser/blob/ef7112d28859ff50f5b1d870fe933579e1d1fd49/libscpi/inc/scpi/types.h#L53-L55 then defines a typedef for bool, which causes a redeclaration error in C++:

../libscpi/inc/scpi/types.h:54:27: error: redeclaration of C++ built-in type 'bool' [-fpermissive]
   54 |     typedef unsigned char bool;
      |

Should __cplusplus be used instead if it is defined to determine which language standard to define for the rest of cc.h? __cplusplus should also have values like 199711L and 201103L.

[j123b567]

You can always define HAVE_STDBOOL=1 yourself - on command line or in scpi_user_config.h so you can try if it fixes the compilation.

Feel free to provide PR which solve this.

[MisterHW]

I think I'm getting away with using

#if (!HAVE_STDBOOL) && (!_GLIBCXX_HAVE_STDBOOL_H)
    typedef unsigned char bool;
#endif

p.s.: as per https://gcc.gnu.org/onlinedocs/libstdc++/libstdc++-html-USERS-4.2/c++config_8h.html , one should not use _GLIBCXX_HAVE_STDBOOL_H directly, but this might be a case where it's warranted.

[j123b567]

C++98 should have stdbool.h so should be fixed by #139

[j123b567]

Please reopen if it is still an issue.