Re: Large writable variables

On 2018-10-16 12:19:55 -0400, Robert Haas wrote:
> On Tue, Oct 16, 2018 at 12:06 PM Andres Freund <andres(at)anarazel(dot)de> wrote:
> > But yea, it definitely should have a big red warning
> > label.
>
> That's all I'm asking. And the warning label shouldn't just say "use
> with caution!" but should rather explain how to know whether you're
> doing the right thing.

I'm thinking of something like:

/*
* Macro that allows to cast constness away from a variable, but doesn't
* allow changing the underlying type. Enforcement of the latter
* currently only works for gcc like compilers.
*
* Please note IT IS NOT SAFE to cast constness away if the variable will ever
* be modified (it would be undefined behaviour). Doing so anyway can cause
* compiler misoptimizations or runtime crashes (modifying readonly memory).
* It is only safe to use when the the variabble will not be modified, but API
* design or language restrictions prevent you from declaring that
* (e.g. because a function returns both const and non-const variables).
*/

Greetings,

Andres Freund