How to unload a type library (.til) programmatically (preferably using IDC, but IDAPython is fine, too)?

Question

TL;DR: I want to do this programmatically using either IDC or IDAPython and failed to find an option that works for me (also scoured idc.idc).

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In order to explicitly load a type library I can use add_default_til() (formerly LoadTil()). However, there doesn't appear to be any counterpart to this function to unload a previously loaded type library. And that's what I am looking for.

My issue is that although %ProgramFiles%\IDA Pro 7.7\sig\pc\autoload.cfg does not list the ntddk64_win7 and ntapi64_win7 type libraries, they seem to get loaded implicitly somehow. Chances are (but I haven't found documentation to corroborate this; the only connection seems to be autoload.cfg) that this has to do with the following log lines:

Using FLIRT signature: Windows Driver Kit 7/10 64bit
Using FLIRT signature: Windows Driver Kit 7/10 64bit
Propagating type information...
Function argument information has been propagated
The initial autoanalysis has been finished.

Now, I'd like to unload those two and instead load ntddk64_win10 and ntapi64_win10 respectively (possibly re-running auto-analysis).

Alas, I haven't found a way to script this.

Bonus question: is there something that ties the FLIRT signatures to type libraries (.til) aside from autoload.cfg?

Answer 1

To unload a type library you can use del_til function from typeinf.hpp.

Usage with IDAPython:

import ida_typeinf

ida_typeinf.add_til("ntapi64_win7", ida_typeinf.ADDTIL_DEFAULT) # load a til file
ida_typeinf.del_til("ntapi64_win7") # unload a til file