[PATCH] D30423: [ubsan] Detect UB loads from bitfields

[Vedant Kumar via Phabricator via cfe-commits]

vsk added a comment.

In https://reviews.llvm.org/D30423#694003, @jroelofs wrote:

> I think this might miss loads from bitfield ivars.


I'll add a test that shows that this case is covered.

> Also, what about the conversion that happens for properties whose backing ivar is a bitfield? (or does that happen in the runtime? can't remember)

I'll also check that synthesized getters have the range check.



================
Comment at: test/CodeGenObjC/ubsan-bool.m:26
+  // OBJC:  [[ICMP:%.*]] = icmp ule i8 [[ASHR]], 1, !nosanitize
+  // OBJC: call void @__ubsan_handle_load_invalid_value
+
----------------
jroelofs wrote:
> vsk wrote:
> > arphaman wrote:
> > > Is it possible to avoid the check here since the bitfield is just one bit wide?
> > No, a user could do:
> > 
> > ```
> > struct S1 s;
> > s.b1 = 1;
> > if (s.b1 == 1) // evaluates to false, s.b1 is negative
> > ```
> > 
> > With this patch we get:
> > ```
> > runtime error: load of value -1, which is not a valid value for type 'BOOL' (aka 'signed char')
> > ```
> What if BOOL is an `unsigned char`, or a `char` that's not signed?
Good point, we don't need to emit the range check if the bitfield is an unsigned, 1-bit wide BOOL. Would you be OK with me tackling that in a follow-up patch?


https://reviews.llvm.org/D30423