21 lines
1.3 KiB
HTML
21 lines
1.3 KiB
HTML
<p>
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Up until now all our data has been allocated on the stack.
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This is fine for most purposes, but limits our ability to hold memory globally, instead of local to a function.
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When a function returns, all of its local data gets popped of the stack and can't be used later.
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Also the stack is smaller than the heap. So even if you only need a giant block of memory in a function, you should allocate it on the heap.
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</p>
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<p>
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To allocate memory on the heap, you use functions like malloc. You have to specify the size in bytes you want to allocate.
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Because the heap doesn't know, when you don't need your data anymore, you have to free it yourself. Otherwise this memory can't be used
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by other processes. This is commonly called a memory leak. To free the memory you call functions like free. You have to pass the pointer to
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the memory you want to free.
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</p>
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<p>
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Unfortunately the heap is slower than the stack. So if you see yourself allocating lots of stuff in a row, maybe think about allocating it in one go and
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use pointer-arithmetic to get pointers with the right offsets.
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</p>
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<p>
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In the following code we have a function that builds an array with all numbers of the Fibonacci sequence up until the n-ths one using the fib-function from earlier in
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the course. But when you run it you will notice that something is wrong. Try to fix it.
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</p>
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