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Predefined symbols in C51

Scott Hughes

Where can I find a list of predefined symbols for C51? I'm trying to write a set of portable library routines and I can't figure out how to tell that the file is being compiled by C51..

So I can do something like:
#ifdef __keil_c51__
//keil specific routines
#endif

I'm using an old version of the compiler, v5.10.

Thanks in advance..

Scott

  • 0 in reply to Scott Hughes

    No, #ifdef __C51__ is exactly what you want!
    This is a pre-processor construct which tests whether or not the pre-processor symbol __C51__ is defined; it does not expand the symbol!

    This is the standard way to check what model of compiler you have; eg,

    #if defined __C51__
//Keil-specific stuff
#elif defined __BORLANDC__
//Borland-specific stuff
#elif defined _MSC_VER
//MSVC-specific stuff
#else
#error Unsupported compiler
#endif

    Having determined that the compiler version symbol is defined, you could then further test its value for version-specific requirements.

    Note that uVision's syntax colouring does not recognise the 'defined' keyword!

  • 0 in reply to Andrew Neil

    I found that symbol in the version 5 handbook also... But I'm not sure if it's useful or not.

    I need:
    #ifdef __C51__
    //Keil-specific stuff
    #endif

    but, since __C51__ returns the version number, that becomes:
    #ifdef 5
    //Keil-specific stuff
    #endif

    So I could do something like:
    #if __C51__>0
    //Keil-specific stuff
    #endif

    But that wouldn't work on other compilers because the symbol wouldn't be defined at all.

    Is there another way to use this symbol to get what I want?

    Thanks for your help!

  • 0

    In the v6.03 manual, "C51 Compiler User's Guide 03.2000," it's on p112, entitled "Predefined Macro Constants"

    __C51__ gives you the version of C51

    There's also a NOEXTEND directive, which disables all the Keil extensions to ANSI C.

    Don't forget that you'll need to consider byte ordering, data sizes, etc, as well as the 'C' language extensions!