Memory does not support stack allocated memory 2 (original) (raw)

At the end of rule 2, this page says:

The DisplayBufferToConsole method now works with virtually every buffer type imaginable: T[], storage allocated with stackalloc, and so on. You can even pass a String directly into it!

There are two issues here:

  1. Memory<T> can't be used with memory allocated on the stack. One link that talks about this, which appears to be the main source for this article, can be seen here. This link says:

Memory<T> cannot be backed by "transient" unmanaged memory; e.g., it is forbidden to back a Memory<T> with stackalloc.

You can also verify for yourself that the following code will not compile:

Memory<int> mem = stackalloc int[10];
  1. The 2nd issue is that a string can't be passed directly into DisplayBufferToConsole. If this is tried, then the C# compiler complains:

Error CS1503 Argument 1: cannot convert from 'string' to 'System.Memory'

Maybe whoever wrote this intended to provide a converter to translate a string into a Memory<T> type. But, if so, it is not present.

I am using the latest version of VS 2019 Community - 16.10.4, which I recently upgraded to. I am also using .NET 6, preview 5 (or maybe preview 6 if it is included with the latest VS 2019 16.10.4 update).

In any case, I would recommend changing the text to read:

The DisplayBufferToConsole method now works for any type of memory allocated on the heap. Memory<T> can't be used with memory allocated on the stack with stackalloc. This is only supported with Span<T>.

The Memory Struct article should also mention that Memory<T> can't be used on stack allocated memory.

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