! for some reason some template names are not found

[mihaisebea]

Unfortunately is not easy to create a simple reproducible case.
It seems that SpecializationID is 0.
I will try to look more into this.

[MetanoKid]

Hi Mihai, thank you for another fix!

I guess the PR can be approved, but I'd like to have some more info on the issue before merging it.
Can you please answer these questions?

• When you collected the trace, which MSVC version was the project compiled with?
• Can you check whether those Unknown templates timeElapsed under the default time to be ignored in the BuildTimeline.json report? I think it's 10ms right now. If it is, it means we'd have this same issue in the timeline report if we passed the timeline_ignore_templates_under argument and it might mean it's a bug in the compiler. Otherwise that'd be an issue in this report.

Thanks 👍

[mihaisebea]

Hi @MetanoKid
I used Visual Studio 2019 16.7.2
Seems the default is indeed 10ms but I have templates that take well over 500ms.

As far as i'm debugging this, in this function:

void TemplateInstantiationsAnalyzer::OnTemplateInstantiation(const CppBI::Activities::TemplateInstantiation& templateInstantiation)
{

there are plenty instantiations that have PrimaryTemplateSymbolKey and SpecializationSymbolKey 0 (zero)
And this is what the event looks like.

[MetanoKid]

Hi Mihai!

I'm afraid GitHub doesn't notify when a comment gets updated and I didn't come back to you sooner. I really apologize.

In the meantime, I tried compiling Unreal Engine from source (because it's a huge project with a lot of templates) in Visual Studio 16.5.2 and 16.7.3, but I wasn't able to reproduce the issue you mention.
However, I tried forcing it by stopping vcperf in the middle of a compilation instead of waiting for it to finish, and that helped me reproduce it.

Long story short, TemplateInstantiation activities are recorded as templates get compiled, but they contain an identifier for that template (PrimaryTemplateSymbolKey and SpecializationSymbolKey, as reported by the SDK) and not its string representation. To get that info, we must wait for SymbolName events to happen.

Indeed, if these SymbolName events don't get emitted, we'll have these entries in the timeline report, which is what I expected when I asked you about it:

Because the SDK didn't emit the expected SymbolName events, we can't really know which template they refer to.
With that in mind, please check my suggestion in the inline comment and tell me what you think about it.

Thank you for your time and interest once again 🙂

[MetanoKid]

How about not registering the Unknown template name at all and switching to this?

auto itSpecializationTemplateName = m_symbolNames.find(pair.second.Specialization);
if (itSpecializationTemplateName == m_symbolNames.end())
{
    // a TemplateInstantiation activity has been recorded but its related SymbolName hasn't been emitted
    // we can't know which template it refers to, so we can only skip it
    continue;
}

After all, it won't be correctly registered in the BuildTimeline.json report either.
And this way users won't have an entry listed Unknown with the accumulated time of (probably) unrelated templates.