Rationale for accepting DIP 1028 as is

[Paul Backus]

On Wednesday, 27 May 2020 at 05:54:32 UTC, Walter Bright wrote:
> On 5/26/2020 1:32 PM, Paul Backus wrote:
>> The reason extern function declarations are particularly 
>> problematic is that changing them from @system-by-default to 
>> @safe-by-default can cause *silent* breakage in existing, 
>> correct code.
>
> Can you post an example of currently compiling and correctly 
> working code that will break?
>
> Setting aside use of __traits(compiles, ...).

I am paraphrasing an earlier post of mine in this thread:

https://forum.dlang.org/post/yvcjpcxfyyobqubjrrxv@forum.dlang.org

The breakage is that functions which are currently correctly 
considered @system will instead be considered @safe. As a result, 
future changes to @safe code are at risk of introducing memory 
corruption.

Strictly speaking, the breakage does not occur until those future 
changes are made, so it is more accurate to say that changing 
un-annotated extern declarations to @safe-by-default will put 
existing code *at risk* of silent breakage. Given the prevalence 
of such declarations in existing code (e.g. [1]), I think it is 
inevitable that this risk will in fact lead to breakage in 
practice, so I do not consider the distinction particularly 
important to draw in this context.

[1] https://github.com/dlang/druntime/pull/3117