Creating arrays

[keen mountain]

I know that arrays either need to have a defined sized, int array[7], or you can just give it data and it will determine the size, int array[]= {1,2,3}, but can I just do int array[];?

[hasty imp]

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[keen mountain]

Also am I allowed to set the size of an array based on a variable like int array[x]? I saw that someone just used malloc when they needed to set a dynamic size

[wooden jasper]

yes?

idk about this tho int array[]= {1,2,3}

[timber path]

It's best practice to malloc and free arrays of variables size. And no, int arr[]; should be replaced with int *arr
More compiker friendly

[keen mountain]

Wdym replaced? How is that used?

[timber path]

An undefined array is problematic with most compilers. A pointer in the other hand can be un initialized pointer in the other hand will not cause problems unless you forget to point it at something later

A pointer and an array are the same semantically

[frank plover]

assuming you meant declaring such array outside of a function / struct declarations - you can, such array will be an incomplete type and must be supplied a size later. see https://en.cppreference.com/w/c/language/type#Incomplete_types & https://en.cppreference.com/w/c/language/array#Arrays_of_unknown_size

[frank plover]

Also am I allowed to set the size of an array based on a variable like int array[x]?
those are called VLAs (Variable Length Arrays). some compilers supports them, some don't. they are generally discouraged though useful in some cases (type declarations for allocations mostly). see https://en.cppreference.com/w/c/language/array#Variable-length_arrays

because they are generally discouraged, it might be best to use *alloc & friends for dynamic allocations (or the functionallity of any established allocator really)