Arrays scoping in threads

How are arrays scoped in C? When do 开发者_JAVA百科they ever get destroyed? (Note, also talk about if they can be passed even in p_threads)

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They're scoped just like normal variables:

// in a function
int arrayA[300];
{
    float arrayB[100];
    // arrayA and arrayB available here
}
// arrayB out of scope, inaccessible.
// arrayA still available.

If you were to pass the array to a function, it would be valid as long as the array was still in scope at the calling site.

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Arrays are scoped like any other primitive, struct or union. Nothing ever gets destroyed in C, though arrays can go out of scope.

Also, just like other types, arrays can be allocated on the heap by calling malloc() to allocate enough space to hold the desired number of elements, and treating the returned void * as a pointer to the first element. Such an array will be valid until you call free().

WRT Pthreads, again the rules are just as for any other type. If you define an array as an automatic (function-scope) variable, it will go out of scope as soon as the function returns; you cannot safely pass a pointer to such an array to another thread. But if you allocate an array on the heap, then you can pass a pointer to this array (to anything inside the array) anywhere you please, including another thread. Of course, you still need to ensure thread-safe access to the contents using appropriate synchronisation mechanisms.

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There's absolutely no difference in scoping and lifetime rules between arrays and any other named entities in C language. I.e. arrays are not special in any way when it comes to scope and lifetime. They behave in that regard just like an ordinary int variable would.