Re: [PATCH] rust: introduce sfile macro for easier code tracing

[Timur Tabi <ttabi@nvidia.com>]

On Wed, 2025-06-04 at 00:15 +0200, Miguel Ojeda wrote:
> On Wed, Jun 4, 2025 at 12:05 AM Timur Tabi <ttabi@nvidia.com> wrote:
> > 
> > But won't that cause the functions to always be compiled and exist in the kernel, even if
> > sfile!()
> > is never used?
> 
> Not necessarily, why?

If I move the function outside of the macro, I need to declare the function as "pub".  If I don't do
this, then other modules that use kernel::sfile won't compile.

But in doing so, the function is compiled as a stand-alone function, even though the macro doesn't
actually use it.  The compiler apparently re-inlines the function in the macro call.  

Compare the two:

Without pub: https://rust.godbolt.org/z/T9YKs3c1r
With pub: https://rust.godbolt.org/z/qEb3x7vbj

I've never actually seen a compiler do this, to be honest, but it makes a lot of sense.  If you
compare the example::main function on both links, they are identical.  But the version with "pub"
also has a full implementation of rfind_const() that is just not used.