1316090 - clang-cl unresolved external symbol NormalizedConstraintSet::BaseRange::FinalizeMerge

Status: RESOLVED INCOMPLETE

(Core :: WebRTC, defect, P2)

Description

[(Away)]

Attachment: mediatrackconstraints

This is due to a recent regression in trunk clang: https://llvm.org/bugs/show_bug.cgi?id=30937

In the meantime this patch can be used as a workaround.

Comment 1

[(Away)]

Attachment: mediatrackconstraints

Bad qref!

Comment 2

[(Away)]

According to https://llvm.org/bugs/show_bug.cgi?id=30937#c1, casting from e.g. "StringRange NormalizedConstraintSet::*" to "BaseRange NormalizedConstraintSet::*" is undefined behavior, and even my workaround has sharp edges. This is unfortunate.

jib, is it possible to write this code in another way that doesn't depend on the pointer-to-member casts?

Comment 3

[Jan-Ivar Bruaroey [:jib] (needinfo? me)]

Yeah your workaround is no good according to that comment.

I should just back this out https://hg.mozilla.org/mozilla-central/rev/c83da3566e98 and use macros instead as someone originally suggested.

It's a shame this isn't supported, as member enumeration can be useful in protecting an algorithm against accidental maintenance mistakes. But it's not, so.

http://stackoverflow.com/questions/28156381/cannot-cast-member-pointer-to-derived-class-to-member-pointer-to-base-class

Comment 4

[Emma Humphries ☕️🎸🧞‍♀️✨ (she/they) [:emceeaich] (Pacific Time) use needinfo]

This is an assigned P1 bug without activity in two weeks. 

If you intend to continue working on this bug for the current release/iteration/sprint, remove the 'stale-bug' keyword.

Otherwise we'll reset the priority of the bug back to '--' on Monday, August 28th.

Comment 5

[Bulk Bug Changes for mreavy's org]

Mass change P1->P2 to align with new Mozilla triage process

Comment 6

[(Away)]

clang-cl no longer gets unresolved symbols for this coding pattern.

Per https://bugs.llvm.org/show_bug.cgi?id=30937#c3 our code is still incorrect, but it's pretty clear from the inactivity on this bug that we're not going to fix this without a blatant error in our face.