On 7/31/19 11:12 AM, Jan Hubicka wrote:
>> and see that in some cases jobserver is 0 and in other cases jobserver is 1.
>> Examples of both:
>> 0 kw -j2 --jobserver-auth=3,6 -- 
>> total 0
>> lrwx------. 1 jakub jakub 64 Jul 31 10:41 0 -> /dev/pts/4
>> l-wx------. 1 jakub jakub 64 Jul 31 10:41 1 -> pipe:[75026106]
>> lr-x------. 1 jakub jakub 64 Jul 31 10:41 10 -> /usr/src/gcc/obj/gcc/libgcc_s.so
>> lr-x------. 1 jakub jakub 64 Jul 31 10:41 13 -> /usr/lib64/libc.so
>> lr-x------. 1 jakub jakub 64 Jul 31 10:41 18 -> /usr/src/gcc/obj/gcc/libgcc_s.so
>> l-wx------. 1 jakub jakub 64 Jul 31 10:41 2 -> /tmp/ccX4y4r3.le
>> l-wx------. 1 jakub jakub 64 Jul 31 10:41 9 -> pipe:[46167136]
>> 1 kw -j2 --jobserver-auth=3,6 -- 
>> total 0
>> lrwx------. 1 jakub jakub 64 Jul 31 10:41 0 -> /dev/pts/4
>> l-wx------. 1 jakub jakub 64 Jul 31 10:41 1 -> /tmp/cchSvmBt
>> lr-x------. 1 jakub jakub 64 Jul 31 10:41 10 -> /usr/lib64/crtn.o
>> lrwx------. 1 jakub jakub 64 Jul 31 10:41 2 -> /dev/pts/4
>> lr-x------. 1 jakub jakub 64 Jul 31 10:41 3 -> /usr/lib64/crt1.o
>> lr-x------. 1 jakub jakub 64 Jul 31 10:41 4 -> /usr/lib64/crti.o
>> lr-x------. 1 jakub jakub 64 Jul 31 10:41 5 -> /usr/src/gcc/obj/gcc/crtbegin.o
>> lr-x------. 1 jakub jakub 64 Jul 31 10:41 6 -> /usr/src/gcc/obj/gcc/testsuite/gcc/c_lto_20081125_0.o
>> lr-x------. 1 jakub jakub 64 Jul 31 10:41 7 -> /usr/src/gcc/obj/gcc/testsuite/gcc/c_lto_20081125_1.o
>> lr-x------. 1 jakub jakub 64 Jul 31 10:41 8 -> /usr/src/gcc/obj/gcc/crtend.o
>> l-wx------. 1 jakub jakub 64 Jul 31 10:41 9 -> pipe:[46167136]
>>
>> so, if one is lucky enough and at least one of the two file descriptors in
>> MAKEFLAGS --jobserver-auth= is closed, it will work fine, but if they are
>> open, even when they have nothing to do with make, it will fail miserably.
> 
> I see, so the problem is that lto-wrapper is executed via plugin from
> gold which already used the file descriptors for something else?
> 
> This seems a bit of problem since gold opens it before we get to
> lto-plugin (most probably) so i do not see how to reliably detect
> presence of make server.

Thank you Jakub for debugging!

> 
> I think the gcc binary can look for jobserv environment, detect jobserv
> and if it is not available remove jobserver option from it prior going
> to ld.  I think this works since I think link-time gcc can only be
> executed via gcc/g++/gfortran... wrappers.

Do you mean something like what I'm attaching?

Anyway, the auto-detection of jobserver seems very ugly to me :/
I tend to remove the support and start working on a proper implementation
that can be used not only by make build system.

Martin

> 
> (unlike lto plugin invoked implicitly for ar/nm etc).
> 
> Honza
>>
>> As a partial workaround, I wonder if jobserver_active_p couldn't check (with
>> fstat/fstat64) if the file descriptors are pipes.  It will still not be 100%
>> reliable, as when you are unlucky the file descriptor could be some
>> completely unrelated pipe, but at least better than the current state.
>>
>> 	Jakub