[webkit-dev] New EWS Non-Unified builder

[Don.Olmstead at sony.com]

When the Mac CMake build is in a working state I'd request an EWS that is Non-Unified as well since Mac builds cover more code.

-----Original Message-----
From: Alex Christensen via webkit-dev <webkit-dev at lists.webkit.org> 
Sent: Thursday, April 29, 2021 8:16 AM
To: dpino <dpino at igalia.com>
Cc: webkit-dev at lists.webkit.org
Subject: Re: [webkit-dev] New EWS Non-Unified builder

I’d be excited to have this.  Those build failures have been bothering me ever since we started using unified builds.  We would have a way to see more problems in our code that are currently hidden.

> On Apr 28, 2021, at 11:45 PM, dpino via webkit-dev <webkit-dev at lists.webkit.org> wrote:
> 
> Hi everyone,
> 
> In Igalia we have been discussing the need of deploying a new builder 
> which builds WebKit using non-unified sources, and we know that at 
> least the folks at Sony are also in favor.
> 
> One side effect of Unified Source building is that it hides 
> compilation errors. The kinds of errors that usually get hidden by 
> unified builds are missing headers inclusions and missing definitions 
> of functions declared inline; the latter being tricky to debug because 
> it results in mysterious linker errors. This is caused by unified 
> builds stashing several .cpp files together for compilation, so the 
> definitions and header inclusions done in one “leak” into the others. 
> As for missing header inclusion errors, a source file might include a 
> header definition as a co-lateral effect of being stashed together 
> with another file that indeed includes the missing header.
> 
> These hidden compilation errors may arise later at some point if 
> unified source files are stashed together in a different manner.
> 
> The current situation is requiring periodical maintenance. You can 
> check build fixes commits due to unified source compilation with:
> 
>    $ git log --pretty=short --grep "Non-unified"
> 
> Here are some examples:
>    https://urldefense.com/v3/__https://bugs.webkit.org/show_bug.cgi?id=222652__;!!JmoZiZGBv3RvKRSx!t22i0IAUrm1zV3LCteGHgJVUHzashK_F9tqjACa4ZTS_y9h8CnFZ7s60jhM-e_2Uo6c$ 
>    https://urldefense.com/v3/__https://bugs.webkit.org/show_bug.cgi?id=222755__;!!JmoZiZGBv3RvKRSx!t22i0IAUrm1zV3LCteGHgJVUHzashK_F9tqjACa4ZTS_y9h8CnFZ7s60jhM-cnURaLI$ 
>    
> https://urldefense.com/v3/__https://bugs.webkit.org/show_bug.cgi?id=22
> 1701__;!!JmoZiZGBv3RvKRSx!t22i0IAUrm1zV3LCteGHgJVUHzashK_F9tqjACa4ZTS_
> y9h8CnFZ7s60jhM-qQl-arU$
> 
> A new builder which builds WebKit with non-unified Source will highly 
> help to improve this situation. Compilation errors will be detected as 
> soon as possible and will save a lot of time not only for the 
> developers who are currently doing this manual maintenance but for 
> anyone who would like to build WebKit, and may stumble on compilation 
> errors accidentally introduced due to unified sources.
> 
> While correct compilation of the codebase can only be guaranteed with 
> non-unified source builds, we do not propose switching the current EWS 
> compilation builders to non-unified because it's slower and the EWS 
> LayoutTests and API test bots use the products built by the EWS 
> builders — we do not want to delay getting results from those. That's 
> why we are proposing a new builder: it will run on parallel, resulting 
> in no slowdown for the other EWS builders, which will keep using 
> unified builds.
> 
> How this new builder will impact developers? The EWS LayoutTest bots 
> take at least 1 hour to complete a build. We think that as long as 
> this new EWS Non-Unified builder is within that time budget, this new 
> EWS wont' slow down development speed.
> 
> Thoughts?
> 
> Best regards,
> 
> Diego
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