winrt::impl::error_ok and friends are duplicated in each translation unit

[dmachaj]

I was running a binary size analysis tool on our optimized binary and the "wasteful duplication" analysis flagged winrt::impl::error_ok and all of the other errors in that same block. These are constexpr so they are in the readonly segment, as expected, but they are duplicated. According to this tool they are 4 bytes each, duplicated 42 times, and add up to 168 bytes each. That adds up to roughly 3KB of our final binary being copies of these error codes.

This can be fixed by changing constexpr to inline constexpr. That syntax will result in them being de-duped to a single copy. It requires C++17, but cppwinrt already requires that so it shouldn't be a problem.

[matbech]

@dmachaj I'm curious, what binary size analysis tool are you using?

[dmachaj]

There is an internal tool that helps with this task. I asked the owner of the tool and I'm not able to share any details regarding the tool at this time :(. Sorry.

[sylveon]

Shame, such a tool sounds really useful

[kennykerr]

https://careers.microsoft.com/ 😋

[AlexBAV]

When I saw this issue, my first impulse was to ask the same question as @matbech.

But then I remembered Bruce Dawson (https://randomascii.wordpress.com/) was once referring to similar tool and after some googling I found that it is called ShowGlobals and is part of Google Chromium repository. You can clone and compile it.

As a hint, the following command will probably need to be executed (in elevated command prompt) before using it:

regsvr32 "C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview\DIA SDK\bin\amd64\msdia140.dll"

The actual path to DIA DLL may differ.

[sylveon]

Seems like the tool is public now: https://www.microsoft.com/en-us/p/sizebench/9ndf4n1wg7d6

[kennykerr]

Yep!