Re: [Boost-build] allowing targets to fail

Subject: Re: [Boost-build] allowing targets to fail
From: Rene Rivera (grafikrobot_at_[hidden])
Date: 2017-04-01 12:51:15

On Sat, Apr 1, 2017 at 6:53 AM, Stefan Seefeld via Boost-build <
boost-build_at_[hidden]> wrote:

> On 31.03.2017 13:35, Steven Watanabe via Boost-build wrote:
> > AMDG
> >
> > On 03/31/2017 11:14 AM, Stefan Seefeld via Boost-build wrote:
> >> Ah, interesting ! So this provides a mechanism to capture a target's
> >> result while still letting if fail. But it seems this comes at a price:
> >> To be able to capture results of individual target builds, I need to
> >> submit them individually (via "UPDATE_NOW"), which precludes
> >> parallelization.
> >> If I submit multiple targets at once, I only get the overall success
> >> back. Correct ?
> >   Yep.  As a workaround, you can batch them, and
> > then call UPDATE_NOW again individually to get
> > the results.  UPDATE_NOW never tries to build
> > any target more than once, no matter how many times
> > it is called from the same b2 process.
>
> I'm actually wondering whether that's (necessary) true: Is the bjam
> engine thread-safe ? If I run `b2 -j 8`, may I invoke UPDATE_NOW from
> one action and expect other targets to continue to be built in parallel
> ? Would that break ? Or would that serialize the execution ?
>

None of the above. Yes, the engine is parallel-safe. But that is irrelevant
for this question. All targets are built with the same mechanism at the low
level. The differences for UPDATE_NOW are when it executes the actions and
how it waits for them. Regular action execution happens after the
parsing/evaluation of the b2 files during the make stages. UPDATE_NOW
happens during the parsing/evaluation and blocks it until the actions
complete. So there's no question about thread safety, or parallel safety,
since b2 is single threaded anyway.

-- 
-- Rene Rivera
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