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Since accessing the memory allocated by `malloc` beyond the size given to the call is undefined behaviour (which means that the standard poses *no* restriction to the behaviour of a program that does this), and since there's no standard way to determine the length of the allocated block, the compiler is indeed allowed to allocate more memory, since there is no standard conforming way for a program to determine whether the allocation was larger than requested.
Note that the standard does not need to give explicit permission for the compiler/standard library to do so, since it already has implicitly given permission by declaring access of that memory as undefined behaviour.

Since accessing the memory allocated by `malloc` beyond the size given to the call is undefined behaviour (which means that the standard poses *no* restriction to the behaviour of a program that does this), and since there's no standard way to determine the length of the allocated block, malloc is indeed allowed to allocate more memory, since there is no standard conforming way for a program to determine whether the allocation was larger than requested.
Note that the standard does not need to give explicit permission for the compiler/standard library to do so, since it already has implicitly given permission by declaring access of that memory as undefined behaviour.

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