Analysis reverts function back to pure after changing the function type

[VisualEhrmanntraut]

Version and Platform (required):

• Binary Ninja Version: 4.3.6874-dev
• OS: macOS
• OS Version: 15.3.1 (24D70)
• CPU Architecture: M3

Bug Description:
If the purity of a function is changed to false, it will be reverted to true on analysis.

Steps To Reproduce:

1. Find pure function
2. Set to non-pure
3. Reanalyse
4. Observe

Expected Behavior:
It should keep the manual change.

[xusheng6]

Thanks for the bug report! However, I am unable to reproduce this on files that I have locally, so I guess it might be something related to the specific file you are working with. Could you please provide us with the file so that we can look into it?

[VisualEhrmanntraut]

@xusheng6 It seems to rather be if I change the function type and not reanalysing

[VisualEhrmanntraut]

Screen.Recording.2025-02-18.at.11.02.12.mov

[VisualEhrmanntraut]

Might be because of this:

>>> demangle_generic(bv.arch, current_symbol.raw_name)[0].pure
BoolWithConfidence(value=False, confidence=0)

[xusheng6]

I think what is happening here is that you set the type of the function, and the property whether a function is a pure function is part of the type, so in other words, you have changed it.

I see that the .pure of the function type is False, but it also has a confidence of 0. I am not sure whether that leads to the analysis to believe the user provided purity is to be ignored, thus auto-analysis took over and set it to True

[VisualEhrmanntraut]

There is still an issue to be fixed, setting the function type with the "Change Type" dialogue also causes that behaviour.

[xusheng6]

@VisualEhrmanntraut can you DM me the file on slack so that we can look into it?

[VisualEhrmanntraut]

Probably not but I will try making a minimal reproduction database for you

[VisualEhrmanntraut]

I sent it. All you need to reproduce the issue is hit Y to change the function type, and then just hit enter. You will see the function goes back to being pure even though it was changed manually to not pure.

[xusheng6]

Simplified repro steps:

1. Create a new binary data, paste 00058052c0035fd6 into it
2. Create a function at 0x0, using the ios-aarch64 platform
3. In the edit function property dialog, uncheck the box for pure
4. Observe the function is not marked with pure
5. Press Y to change the type, e.g., to bool sub_0
6. Observe the function becomes pure again