[PATCH] Change how we deal with (implicit) -fno-rtti + -fsanitize=vptr

[Filipe Cabecinhas]

This is getting a bit hard to reason about.

Here are the pieces:

- Default RTTI behavior for target (depends on other arguments like the type of input file)
- RTTI related options (explicit)
- Sanitizer options (explicit (vptr) or implicit (undefined))

SanitizerArgs _wants_ to hide details like “which sanitizers exist/are enabled”, which means it will have to sort out whether to warn/error or not by itself (it needs to know if there's an explicit RTTI-related argument) .

The RTTI-related code needs to know if C++ exceptions are on to decide if it implicitly turns on RTTI or not (this implies knowing not just the arguments, but also the input file).

To decide whether we need additional args for RTTI or not, and which ones to pass, we need to know the RTTI-related arguments passed and the input type (actually, we need IsCXX(Input)).

Easiest (kind of hacky) solution: Add enough arguments to getSanitizerArgs and to the SanitizerArgs constructor to allow it to decide whether to warn/error due to the vptr sanitizer (We'd parse the RTTI-related args, and use those results (enabled/disabledexplicitly/disabledimplicitly + an RTTI-related arg, if necessary) when calling getSanitizerArgs()).

Easy (kind of hacky) solution (with a major drawback): Make it easy to, via SanitizerArgs, add/remove sanitizers. It would be hard to know if the vptr sanitizer was enabled explicitly or via -fsanitize=undefined, with this solution (we'd have to re-parse everything, if we wanted to keep it working that way).

Non-hacky solutions: Sorry, couldn't think of one. Additional ones included stashing stuff in the ToolChain object… It doesn't seem like it's the proper thing to do.


http://reviews.llvm.org/D7525

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