Bugzilla Bug 209272

erlang uses the kpoll flag but contains a typo. This is the case at least with
12.2.0 and 12.2.1.


Reproducible: Always

Steps to Reproduce:




Apparently fixing this typo does not cause erl to recognize kpoll:

#erl
Erlang (BEAM) emulator version 5.6.1 [source] [smp:1] [async-threads:0] [hipe]
[kernel-poll:false]

..even though configure recognized the option, but still selected "epoll".
Might just be a problem with the erl output though.
The typo needs to be fixed in any case.

Created an attachment (id=142912) [edit]
fix for USE="kpoll" typo to pass the correct option to configure

This typo was there since this...

  24 Feb 2007; Christian Faulhammer <opfer@gentoo.org>
  +erlang-11.2.3-r1.ebuild:
  added smp and kpoll USE flags to enable/disable those features, adjusted
  some bits; thanks to Max Loparyev <max@city.veganet.ru>

nearly one year and nobody noticed.

Fixed.

Great, thanks. FWIW I figured out the kpoll mystery - you have to start erl
with "+K true" to explicitly make it use kpoll:
holger>erl +K true     
Erlang (BEAM) emulator version 5.6.1 [source] [smp:1] [async-threads:0] [hipe]
[kernel-poll:true]

so the flag works and all is good. :)

(In reply to comment #3)
> Great, thanks. FWIW I figured out the kpoll mystery - you have to start erl
> with "+K true" to explicitly make it use kpoll:

 How can this be activated by default?  Because someone requesting USE=kpoll
wants it to work out of the box.

Good question. The easiest/non-intrusive way seems to be to define a default
environment variable as documented in man erl. There are two, ERL_FLAGS
(appended to the end of the commandline) and ERL_AFLAGS (prepended to the
beginning) so it seems ERL_AFLAGS is a good candidate for setting defaults.
Overriding works too:

holger>unset ERL_FLAGS 
holger>unset ERL_AFLAGS
holger>erl
Erlang (BEAM) emulator version 5.6.1 [source] [smp:1] [async-threads:0] [hipe]
[kernel-poll:false]

holger>export ERL_AFLAGS="+K true"
holger>erl                        
Erlang (BEAM) emulator version 5.6.1 [source] [smp:1] [async-threads:0] [hipe]
[kernel-poll:true]

holger>erl +K false               
Erlang (BEAM) emulator version 5.6.1 [source] [smp:1] [async-threads:0] [hipe]
[kernel-poll:false]

Looks like a reasonable approach instead of patching around in the source,
right? The argument handling can be found in erts/etc/common/erlexec.c:main but
that seems to be the wrong place to force +K. A quick read through the various
erl_poll.(c,h) files didn't show any simple switches either.