CODEWITHSUNDEEP
ccompiler-constructionstaticextern
dragon135
dragon135

Reputation: 1376

How to declare not yet defined static variable in C

How to declare static variable prior to its definition? The use case is there is other global variable is using it before it is defined. And I don't want to move the definition to top.

Example code:

extern static int a; //compiler error, but I need to declare 'a' because it is used below by 'x'

typedef struct{
 int * dd;
}X;

static X x={&a}; //this variable needs to use 'a'

static int a=5; //this is where 'a' defined

Above code is compile error.

=== Update ====

Well, I found the solution myself. Just remove the extern keyword.

Upvotes: 0

Views: 175

Answers (3)

ashutosh
ashutosh

Reputation: 79

You cannot have two storage classes used on one single variable. Doing this will flag an error

Upvotes: 0

Spundun
Spundun

Reputation: 4034

Read http://www.learncpp.com/cpp-tutorial/43-file-scope-and-the-static-keyword/

In your example, the variable is declared static in the file scope. This means that it's available to all the code in the file.

In such a case it doesn't make sense to define it below the code that it uses. You should simply move it to the top of the file.

Also checkout Forward declaring static C struct instances in C++ if you have a need to do this for some reason. May be the solution provided there could be adapted to fit your larger goal.

Upvotes: 1

Pranit Kothari
Pranit Kothari

Reputation: 9841

You are trying to use two storage classes at a time. Thats problematic. Use static int a;, and you can access it in your file, just make sure you are defining it above the code you are using it.

Upvotes: 2

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