Bug 39626 – WebCorePrefix.h should not include wtf/UnusedParam.h

• Status: RESOLVED
• Resolution: INVALID
• Component: WebCore Misc.

[Eric Seidel (no email)]

WebCorePrefix.h should not include wtf/UnusedParam.h

This causes confusion like:
https://bugs.webkit.org/show_bug.cgi?id=39623#c5

Chromium doesn't use a prefix header so that they can support distcc 3 push mode which doesn't support prefix headers (but is much much faster than distcc 2).

Until Apple's XCode supports distcc 3 push mode (which it might soon?) the rest of WebKit maybe doesn't care, but removing this one include would make this type of failure less common.

[Mark Mentovai]

Xcode 3.2.2 supports distcc pump mode. It allows for prefix headers, but disables precompilation, so there isn’t much advantage to the prefix header (and there may in fact be a disadvantage). The advantage of letting the distcc server do preprocessing generally outweighs having a precompiled prefix header.

[Alexey Proskuryakov]

Do I understand it right that such a change would:
1) prevent confusion like cited above (I guess I'm still confused, as I don't understand how it's related to unreachable code);
2) have no change on chromium build speed;
3) make builds slower for others?

[Mark Mentovai]

I don’t know. I’m trying to figure out this bug report, but in the current trunk, WebCorePrefix.h doesn’t #include wtf/UnusedParam.h, or anything else in wtf, or anything else in all of JavaScriptCore (except when defined(ANDROID)).

I think a few distinct concerns have been conflated here. Eric, what’s your intent?

[Eric Seidel (no email)]

I also dug through the WebCorePrefix.h chain and failed to find how wtf/UnsuedParam was getting included.  Maybe it was't through WebCorePrefix, in which case this bug is invalid.  However something has caused this build error twice in the last week for Chromium when folks (like myself) have used UNUSED_PARAM on mac and its built fine, and then it fails to build on the chromium bots.  I suspected prefix headers, but that may not be the cause.

[Mark Mentovai]

Does it work properly in the Chromium Mac and Apple WebKit build but not the other platforms, or does it only work in the Apple WebKit build and not in the Chromium Mac build?

[Eric Seidel (no email)]

I don't think I have enough information to continue a useful bug report now my original theory failed. :)  I think I'll wait for this to come up again and try attacking it then.

Thank you both for your input.