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Re: [PATCH] Deduce automatically number of cores for -flto option.


Hi,

> We do not detect jobserver because of Dejagnu is not using it.
> And yes, we default to -flto=<numthreads> in LTO tests now. That's
> what is causing issues right now.

Why the error messages are 
make[4]: *** write jobserver: Bad file descriptor.  Stop.
make[4]: *** Waiting for unfinished jobs....
make[4]: *** write jobserver: Bad file descriptor.  Stop.
It seems to me that it is internal make from lto-wrapper trying to get
jobserver access?

> Works for me.

We probably also can give it a meaning controlling the default parameter
of -flto.
I.e. setenv GCC_LTO_PARALLELISM <numthreads/auto/jobserv>
which we will default to in case only -flto is passed to command line.

Make's jobserver is quite nice and easy to use. If it supported named
pipe and there was a small library which allowed to initialize jobserver
and connect to it, perhaps other tools needing parallelism during build
(GCC, ninja, llvm, ...) would be able to use common protocol.

Honza


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