Changing a variable to a constant.

This is a discussion on Changing a variable to a constant. within the C Programming forums, part of the General Programming Boards category; Hi, I have a question about changing a variable to a constant. My problem arrises using Texas Instruments' CCS3.1 compiler. ...

  1. #1
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    Changing a variable to a constant.

    Hi,
    I have a question about changing a variable to a constant.

    My problem arrises using Texas Instruments' CCS3.1
    compiler. The following boiled down code builds finely in Microsofts VC6, but not in CCS:

    Code:
    void main(){
    	 const int bufsize = 2;
    	 int splitbuf[bufsize]; //line 5.
    }
    In CCS I get the following error message:

    "arrTest.c", line 5: error: expression must have a constant value

    Does anyone have a suggestion for a workaround, that will make it possible for me to change a variable into a constant so my program will compile in CCS?

    Best regards, Esben.

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    The const keyword actually means "read only" in C. For true constants, C programmers usually use #define's - constant symbol, or, you could hard-code a constant value into your source code but the former is more used, for good reasons.

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    Hi xeddiex,
    thanks for your reply. I am aware of the #define option. I guess my problem needs a bit more specification:

    My code looks more simular to the following:

    Code:
    #define BUFSIZE(x,y) ((x)+(y))
    void main(){
    	const int x = 2;
    	const int y = 3;
    	const int bufsize = BUFSIZE(x, y);   
    	int splitbuf[bufsize]; 
    }
    It will work in VC6 if I remember to declare all the integers as const, but CCS ...buhuu... still sees 'bufsize' as a variable.

    Provided this new information, does anyone have an idea how to make my bufsize constant?

    Best regards, Esben.

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    I think you're compiling in C++. Make sure your file extension ends in .c, not .cpp.

  5. #5
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    #define X 2
    #define Y 3
    int splitbuf[BUFSIZE(X,Y)];

    > It will work in VC6 if I remember to declare all the integers as const
    This is what happens when you learn an implementation rather than the language.
    When you move to another compiler, it's always the same old "but it works on...." questions.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

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    DOH! Thanks for the enlightenment.

    So now the question is if there is a bug in the original open source c code, that is not noticed by the MSVC... Guess I gotta look into that.

    Thanks again!
    So long.

  7. #7
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    > So now the question is if there is a bug in the original open source c code
    There's a pretty good chance (the void main isn't a good sign in itself).

    Compiling with a new compiler not only shows up all the compiler extensions which were previously used, it's also likely to show up various memory problems which just happened to go unnoticed in the old system, but due to different alignment, ordering and initialisation state cause all sorts of problems in the new system.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

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