Re: Improving math function wrappers

[Florian Weimer <fweimer at redhat dot com>]

On 03/16/2017 02:52 PM, Wilco Dijkstra wrote:
> While the wrappers may be bypassed when building with -Ofast, this uses C header
> magic (ie. it doesn't work in languages other than C and C++). Given other languages
> don't even have the concept of errno, C99 doesn't require it, and no application ever
> reads errno, it is inefficient to force the use of the wrappers in almost all cases.

What's the expensive part?  Computing what errno value to set, or 
obtaining the location of errno?

We have recently removed the PID cache from the TCB.  We could store the 
errno value there, instead of going through __errno_location.  (Code 
outside glibc would still use __errno_location, of course.)

Florian