[PATCH] D24048: [Driver] [Darwin] Add sanitizer libraries even if -nodefaultlibs is passed

[Dmitri Gribenko via cfe-commits]

gribozavr added a subscriber: gribozavr.
gribozavr added a comment.

> If a user specifies "-fsanitize=<blah>" I think it is expected that the sanitizer library would be included on the link line.


I deeply disagree.

If the user asks for `-nodefaultlibs`, we should not add any libraries ourselves, because (a) this is what they asked for, and (b) they probably know what they are doing if they are using such a low-level flag.  (And they are probably doing something deeply system-specific and they can handle adding more low-level compiler options.)

There are issues with the behavior you are proposing.  If `-nodefaultlibs` adds some runtime libs, but not others, it is:

- confusing,
- inconsistent -- users can't predict the behavior of a given set of compiler options.  How would you document `-nodefaultlibs` with the semantics that you propose without explicitly explaining this special-case interaction with sanitizers?  If you can't, then it means that the design is not the right, intuitive one.
- The proposed semantics lead to an immediate feature request for a `-really-nodefaultlibs` option that does not add sanitizer libraries,
- The proposed semantics add to an existing mess of the random special-case driver behavior.

So the question becomes, what are you trying to do?  If you want to allow users to easily link in the sanitizer runtime even if they specify `-nodefaultlibs`, I think the user should explicitly opt into that via another driver flag (e.g., `clang -nodefaultlibs -fsanitize=address -flink-sanitizer-runtime=address`).  Then the command line is explicit about the intent, and each flag has the obvious meaning.


https://reviews.llvm.org/D24048