DIP 1025--Dynamic Arrays Only Shrink, Never Grow--Community Review Round 1

Dennis dkorpel at gmail.com
Mon Nov 11 13:13:39 UTC 2019

On Monday, 11 November 2019 at 11:26:49 UTC, Nicholas Wilson 
> is functional identical, thus any issues present in 2 are also 
> present in 1. The suggestion that doing so in a loop would 
> create more garbage is false as it is functionally identical.

There is a difference: a = a ~ b is guaranteed to make a copy 
while a ~= b might just use spare capacity of the memory that 
slice `a` refers to.


This is what the dead/alive example is supposed to express.
It is still true however that the rationale is not very 
The first example indeed doesn't show any benefits of the DIP:

int[] slice = cast(int*)malloc(10 * int.sizeof)[0 .. 10];
slice = slice ~ 1; // now guaranteed to make a copy
free(slice.ptr); // Still oops

The following claim in the DIP is also unsubstantiated:

> This change is a necessary part of D evolving towards being 
> memory safe without using
> a GC.

I would like to see an example of memory corruption in `@safe` 
code that can happen because of slice appending.

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