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may i declare an array with a global element in C?
Can i declare with a const type? It runs on Xcode, however I fear it isn't correct, because glob is not a const type (same thought on static type).

#include <stdio.h> #include <stdilib.h> int glob; void main (){ int const con; static int stat; int arr[glob]; int arr2[con]; int arr3[stat]; }

In addition, I'm in need of practicing finding mistakes in C code and correcting them for a test (CS student) and could not find a resource for it.

thank you in advance.

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    int const con; is useless, as the variable(!) is not initialised. C does not have symbolic constants like C++ or Pascal. They are all different languages. And writing const after the type is an obsolescence feature; write const int i = ...; instead. Commented Feb 22, 2016 at 22:16
  • Just to make clear: if you expect the array to resize when the variables change, you are wrong. Commented Feb 22, 2016 at 22:32
  • I've changed my mind. This is the real duplicate: stackoverflow.com/q/18848537/3745896 Commented Feb 22, 2016 at 22:38
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    int glob; ...int arr[glob] is invalid ref as glob is 0. Commented Feb 22, 2016 at 22:41

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Globals and statics are automatically initialized to 0 if an initializer isn't provided. The variable con local to main however isn't, so its value is undefined.

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22 Comments

there is another problem here. You can't declare arrays of size zero. But this is not the question.
@River - int const con;, does it not?
Actually con is uninitialised, resulting in UB. Even worse, it cannot get a value assigned. stat is not.
@River - Oh jeez, brain fart. Fixed.
@Michi: Because he fell into the same trap as I did? And because he did not really answer the actual question.
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may i declare an array with a global element in C?

With C99 and optionally in C11, variable length arrays (VLA) are supported.
Array length must be more than 0.

int glob; void main (){ int arr[glob]; // bad array length 0 int arrX[glob+1]; // OK array length > 0

Can i declare with a const type?

With VLA, yes, it is irrelevant if the type of the array size is const or not.

// Assume VLAs are allowed int a[5]; // OK 5 is a constant const int b = 4; int c[b]; // OK int d = 7; int e[d]; // OK

With non-VLA, the array size must be a constant. A variable, const or not, is no good.

// Assume VLAs not allowed int a[5]; // OK 5 is a constant const int b = 4; int c[b]; // No good, b is not a constant.

In addition, I'm in need of practicing finding mistakes in C code and correcting them for a test

Enable all warnings of your compiler is step 1.

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