[clang] [clang][ptrauth] Warn about the use of a weak signing schema (PR #157779)

[Kristof Beyls via cfe-commits]

kbeyls wrote:

Thanks for this contribution @martinuy !

My first thought when seeing this warning is that potentially many developers who happen to be targeting a platform with pointer authentication may not understand well enough why a particular signing schema is weak and how they could or should change it.

Side thought: Would this warning only trigger on variables where a developer has explicitly added something to the source code to request a non-default signing schema? (In that case, chances are higher that the developer may be able to understand the warning well).

Basically, I'm wondering if there already is clang documentation that explains why a particular signing schema may be weak. If not, I'm wondering if it could be added somewhere. The most obvious place might be to somehow add it somewhere to https://clang.llvm.org/docs/PointerAuthentication.html?
I'm assuming that a developer who does not understand the warning well may do a web search with the produced warning, and ideally they should find a reasonable explanation when doing so.


https://github.com/llvm/llvm-project/pull/157779