search

ianlancetaylor / demangle

C++ symbol name demangler written in Go
BSD 3-Clause "New" or "Revised" License
166 stars 24 forks source link

Support demangling __Z (two underscores) automatically #22

Open xPaw opened 1 month ago

xPaw commented 1 month ago

There's this code:

https://github.com/ianlancetaylor/demangle/blob/81f5be970ecae4046912a026004100b0535be16e/demangle.go#L153-L156

I don't see why it can't support double underscores by itself either. Currently it requires manually stripping the underscore, but then it breaks demangling strings that already have only one underscore.

For example: echo "__Znwm" | c++filt -_

ianlancetaylor commented 1 month ago

On any given system, the C++ compiler will generate either __Znwm or _Znwm. It would be incorrect to discard a leading underscore on systems that don't add a leading underscore. So it should never be the case that manually stripping an underscore can break demangling strings. You should strip a leading underscore if your symbols have leading underscores, and not strip it if you don't.

xPaw commented 1 month ago

Is there a practical case where this could cause issues?

This tool in particular does it automatically (it also handles Windows symbols by itself too, so there's that) https://github.com/nico/demumble

ianlancetaylor commented 1 month ago

In my opinion doing it automatically is unwise. It will do the wrong thing in some cases. It should never be ambiguous whether a symbol might or might not be a mangled name.