On Thu, Oct 12, 2017 at 2:53 PM, Keith Miller <keith_mil...@apple.com> wrote:
> Hello WebKittens, > > As discussed previously, I’m preparing to start migrating WebCore to > unified-source builds. I was originally going to move over in one step but > I have since realized that is going to be super hard to rebase fast enough. > Instead I’ll move WebCore over incrementally. I have a full build of webkit > working locally with both CMake and Xcode. The debug build time on my MBP > went from ~25min to ~9min. There are still a bunch of files that don’t work > with unified sources (mostly .mm files) that I will try to fix later. > > I had to make a bunch of source changes in order to get things to work > (see: https://bugs.webkit.org/show_bug.cgi?id=178229): > > 1) Move all “using namespace <name>;” inside the WebCore namespace (they > used to be in the global namespace) and change to "using > WebCore::<type-name>;” in .mm files. > 2) Move a bunch of the soft linking library/framework macros out of the > .mm files since those caused name collision problems. > 3) Fix minor other naming collisions. > > It seems like we are already moving away from 2 with PAL so I’m hoping > that’s not contentious. > > The problem with 1 in a unified source world is generic names often > collide with system header names. For example, WebCore has a Rect class and > that collided with a system header type elsewhere. Thus, I propose that we > change our style rules to forbid "using namespace” in the global scope and > only allow them inside namespaces. We already have a stricter rule in > headers so it doesn’t seem like a big change to apply this rule to .cpp > files. Interestingly, it looks like JSC never followed the global namespace > “using namespace" rule we currently have. Obviously, we’d need to update > https://webkit.org/code-style-guidelines/, regardless of our final style > choice. > Forbidding "using namespace" in the global scope seems fine. That's just a bad practice anyway. - R. Niwa
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