Variably modified array at file scope

Question

I want to create a constant static array to be used throughout my Objective-C implementation file similar to something like this at the top level of my   m  file   static const int NUM TYPES   4  static int types NUM TYPES         1    2     3     4      I plan on using NUM TYPES later on in the file so I wanted to put it in a variable   However  when I do this  I get the error      Variably modified  types  at file scope    I gather that this may have something to do with the array size being a variable  I don t get this message when I put an integer literal there  like static int types 4     I want to fix this  but maybe I am going about it all wrong   I have 2 goals here    To have an array which is accessible throughout the file To encapsulate NUM TYPES into a variable so I don t have the same literal scattered about different places in my file   Any suggestions    EDIT  Found this in the C Faq  http   c-faq com ansi constasconst html

User · Answer

define NUM TYPES 4

User · Answer

As it is already explained in other answers  const in C merely means that a variable is read-only  It is still a run-time value  However  you can use an enum as a real constant in C   enum   NUM TYPES   4    static int types NUM TYPES         1  2  3  4

User · Answer

Imho this is a flaw in many c compilers  I know for a fact that the compilers i worked with do not store a  static const variable at an adress but replace the use in the code by the very constant  This can be verified as you will get the same checksum for the produced code when you use a preprocessors  define directive and when you use a static const variable   Either way you should use static const variables instead of  defines whenever possible as the static const is type safe

User · Answer

The reason for this warning is that const in c doesn t mean constant  It means  read only    So the value is stored at a memory address and could potentially be changed by machine code

User · Answer

It is also possible to use enumeration   typedef enum       typeNo1   1      typeNo2      typeNo3      typeNo4      NumOfTypes   typeNo4    TypeOfSomething

User · Answer

If you re going to use the preprocessor anyway  as per the other answers  then you can make the compiler determine the value of NUM TYPES automagically    define NUM TYPES  sizeof types   sizeof types 0   static int types          1    2     3     4

[c] Variably modified array at file scope

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