1634949 - error: aggregate initialization of type 'mozilla::dom::IpdlQueueBuffer' with user-declared constructors is incompatible with C++20 [-Werror,-Wc++20-compat]

Status: RESOLVED FIXED

(Core :: Graphics: CanvasWebGL, defect)

Description

[Sylvestre Ledru [:Sylvestre]]

with clang trunk

In file included from UnifiedProtocols11.cpp:83:
In file included from /var/lib/jenkins/workspace/firefox-clang-lld-last/obj-x86_64-pc-linux-gnu/ipc/ipdl/PCompositorBridge.cpp:26:
In file included from /var/lib/jenkins/workspace/firefox-clang-lld-last/obj-x86_64-pc-linux-gnu/ipc/ipdl/_ipdlheaders/mozilla/dom/PWebGLParent.h:20:
/var/lib/jenkins/workspace/firefox-clang-lld-last/obj-x86_64-pc-linux-gnu/dist/include/mozilla/dom/IpdlQueue.h:240:43: error: aggregate initialization of type 'mozilla::dom::IpdlQueueBuffer' with user-declared constructors is incompatible with C++20 [-Werror,-Wc++20-compat]
               toSendSync, IpdlQueueBuffer{mId, std::move(mSerializedData)})
                                          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.

Comment 1

[Sylvestre Ledru [:Sylvestre]]

David, could you please have a look?
thanks

Comment 2

[(Away)]

It's interesting that this only happens on trunk. The warning message dates back to clang 8 so we should have seen it sooner. Maybe the conditions for "has a user-declared constructor" have changed? The constructor for IpdlQueueBuffer looks pretty vanilla to me!

Comment 3

[David Parks [:handyman]]

I'll take clang's word for it and switch to a normal constructor. I can't keep track of all of the list constructor exceptions.

Comment 4

[David Parks [:handyman]]

Attachment: Bug 1634949: Avoid list-initializer construction in WebGL IpdlQueueBuffer r=jgilbert!

The list-initialization previously used is illegal for this case in C++20.

Comment 5

[Kelsey Gilbert [:jgilbert]]

Here's a fairly good rundown of the breaking change made in c++20:
https://stackoverflow.com/questions/57271400/why-does-aggregate-initialization-not-work-anymore-since-c20-if-a-constructor

Comment 6

[(Away)]

This error comes up in clang 10 as well.

Comment 7

[David Parks [:handyman]]

Actually managed to convince me it makes sense.

Comment 8

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/385f49adaf00
Avoid list-initializer construction in WebGL IpdlQueueBuffer r=jgilbert

Comment 9

[Kelsey Gilbert [:jgilbert]]

Yeah I'm not thrilled about it, but I see why they did it. I wish I had a way to trivially declare a defaulted aggregate constructor, though.

Comment 10

[Alexandru Michis [:malexandru]]

https://hg.mozilla.org/mozilla-central/rev/385f49adaf00

Comment 11

[BugBot [:suhaib / :marco/ :calixte]]

Set release status flags based on info from the regressing bug 1621762

Comment 13

[BugBot [:suhaib / :marco/ :calixte]]

The patch landed in nightly and beta is affected.
:handyman, is this bug important enough to require an uplift?
If not please set status_beta to wontfix.

For more information, please visit auto_nag documentation.

Comment 14

[David Parks [:handyman]]

Comment on attachment 9145649 [details]
Bug 1634949: Avoid list-initializer construction in WebGL IpdlQueueBuffer r=jgilbert!

Beta/Release Uplift Approval Request

• User impact if declined: None. This code is not live. The impact is to anyone investigating clang-trunk builds or in the event that clang-trunk is promoted while this is still in repo.
• Is this code covered by automated tests?: No
• Has the fix been verified in Nightly?: Yes
• Needs manual test from QE?: No
• If yes, steps to reproduce:
• List of other uplifts needed: None
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky): The code is not in any execution path (requires changing a config setting).
• String changes made/needed: N/A

Comment 15

[Pascal Chevrel:pascalc (PTO until April 26)]

Comment on attachment 9145649 [details]
Bug 1634949: Avoid list-initializer construction in WebGL IpdlQueueBuffer r=jgilbert!

Low risk and regressed in 77 nightly, uplift approved for beta, thanks.

Comment 16

[Sebastian Hengst [:aryx] (needinfo me if it's about an intermittent or backout)]

https://hg.mozilla.org/releases/mozilla-beta/rev/38713cb5f784