Re: How are rustc -Z flags enabled during build?

[Daniel Xu <dxu@dxuuu.xyz>]

Hi Gary, Miguel,

On Thu, Sep 02, 2021 at 07:50:44AM +0200, Miguel Ojeda wrote:
> Hi Daniel,
> 
> On Thu, Sep 2, 2021 at 1:11 AM Daniel Xu <dxu@dxuuu.xyz> wrote:
> >
> > When I try to run it outside of kbuild, I get:
> >
> >     error: the option `Z` is only accepted on the nightly compiler
> >
> > How does kbuild use the -Z features on a stable rustc?
> 
> As Gary points out, it is an environment variable being set in the
> top-level `Makefile` nearby the other flags. I considered adding it to
> the command-line instead so that copy-pasting the lines is easier,
> even if it means being a bit more verbose.
> 
> In any case, note that it is an escape hatch intended to be internal
> to the compiler (which explains the error message not mentioning it)
> and thus should be avoided unless a project has very special
> constraints.
> 
> Our goal is to drop its usage as soon as it is feasible, but it will
> take a while. It is also why we only maintain support for a given
> `rustc` version for the moment.
> 
> Cheers,
> Miguel

Thanks! I knew there must've been some magic somewhere :) .

Daniel