On Mon, Jun 07, 2021 at 12:52:15PM +0200, Peter Zijlstra wrote:

On Sun, Jun 06, 2021 at 03:26:16PM -0500, Segher Boessenkool wrote:

quoted

I am saying that if you depend on that some C code you write will result
in some particular machine code, without actually *forcing* the compiler
to output that exact machine code, then you will be disappointed.  Maybe
not today, and maybe it will take years, if you are lucky.

(s/forcing/instructing/ of course, compilers have feelings too!)

And hence the request for a language extension. Both compilers have a
vast array of language extensions that are outside of the C spec (thank
you!), so can we please get one more?

I don't see why not?  It will need to be well-defined, so that it *can*
be implemented.  And ideally it will be useful for other applications as
well.  Finally, it should "play nice" with other extensions and language
features.


Segher