Missing variable declaration in hlil

[yrp604]

Version and Platform (required):

• Binary Ninja Version: 3338-dev
• OS: Windows
• OS Version: 11

Bug Description: A variable seemingly comes out of nowhere

Steps To Reproduce: Please provide all steps required to reproduce the behavior:

1. Open KernelBase.dll
2. Load the pdb
3. Navigate to GetModuleHandleW
4. Look at the usage of arg_8 -- this variable should show up in the function signature, and as is just appears at it's use site without a corresponding def site in the function

Expected Behavior: Every variable that is used has a definition.

Screenshots:

Additional Information: KernelBase.dll.txt

[fuzyll]

User reports this still repros on latest dev and the container fix from last week doesn't affect it.

[yrp604]

This seems to be due to the calling convention allowing for the use of the register spill area as scratch space, documented here: https://devblogs.microsoft.com/oldnewthing/20110302-00/?p=11333

[plafosse]

as of 4.2 the code looks like this now which seems almost perfect.

[yrp604]

This isn’t fixed? Where is the declaration for result in your screenshot?

[plafosse]

🤦‍♂️ Yeah IDK what I was thinking

[D0ntPanic]

Fixed in 5.0.7156