Add to comment for lambdas.

Add comments to tests, and add a test for non instantiated trivial ctor and one for lambdas.

Update ctor homing check, and add some test cases.

In D87808#2282223, @rnk wrote:

In D87808#2280197, @dblaikie wrote:

@rsmith What's the deal with these anonymous structs/unions? Why do they have copy/move constructors (are those technically called from the enclosing class's copy/move constructors?) but no default constructor to be called from the other ctors of the enclosing class?

Yes, I'm curious: copy and move constructors require an object of this type to already exist in memory. Is there a well-defined way of creating an object of this type in memory when it has no other constructors?

Maybe the issue is that this code is running into the lazy implicit special member declaration optimization. Maybe the class in question has an implicit, trivial, default constructor, but we there is no CXXConstructorDecl present in the ctors list for the loop to find.

whoops, sorry for weird formatting in the previous comment.

This is causing a link error in the windows chromium build:

Ah, yeah. I'm not really sure if there could be cases where there is no size. If there are, I guess we shouldn't make any changes here.

rebase

update test

remove assert; edit test case

ah sorry, this was relanded in b1009ee84fc0242bcebd07889306bf39d9b7170f.

Fix errors.

just reopening to update the diff.

In D86491#2235206, @MaskRay wrote:

Note that Harbormaster actually reported the check-clang-codegencxx issues B69369..

unfortunately not any thorough testing :) I just happened to notice it the last time I looked at this code

Simplify test and add comments.

Add unit test and comment.

I think that makes sense.

Oh no, I'll upload the file here since I'm not sure how to make the bug visible again: https://reviews.llvm.org/F12619177

Ok, I think the actual object file diff comes from this file: https://github.com/chromium/chromium/blob/master/sandbox/linux/syscall_broker/broker_command.cc
I checked that the test fails if I only build this object file with this change.

Actually, I've looked into it more and I think that isn't the correct object file. I'm bisecting to figure out which object file change causes the test failure. Sorry about that!

Sorry, I was hoping the object file diff would be clearer. If it could be reverted in the meantime, that would be helpful. I'm not sure if I'll be able to make an actual reproducer, but I'll at least try to narrow down the object file change.

I haven't been able to make a simple reproducer, but I attached a reproducer for compiling the object file here: https://crbug.com/1114852.

Add more extensive check that -fuse-ctor-homing only does something when -debug-info-kind=limited

In D85799#2214330, @dblaikie wrote:

If possible, could you test the negative cases too? That -fuse-ctor-homing doesn't override -debug-info-kind=line-tables-only or no -debug-info-kind at all?

Yep, just added a line to the existing ctor homing test case.

Add test case.

This is causing test failures / crashes in several chromium android tests (https://crbug.com/1114852). I'm not really familiar with this code, but it seems like after this change, there are some lines missing in the assembly.

whoops, forgot about this patch; not sure who to add as reviewer?

remove change to add class types to retained types list,

In D84870#2182463, @dblaikie wrote:

I think it'd be good to separate these two issues/patches.

In part because I'm curious whether, even with a trivial ctor - if we did the retained types thing - would that be enough?

more cleanup