================
@@ -4022,8 +4169,36 @@ LValue CodeGenFunction::EmitArraySubscriptExpr(const
ArraySubscriptExpr *E,
ArrayLV = EmitArraySubscriptExpr(ASE, /*Accessed*/ true);
else
ArrayLV = EmitLValue(Array);
+
auto *Idx = EmitIdxAfterBase(/*Promote*/true);
+ if (SanOpts.has(SanitizerKind::ArrayBounds)) {
----------------
rjmccall wrote:
Yeah. Specifically, I was thinking that you already have the address of this
flexible array member, and if the immediately containing struct is uniquely
allocated directly within the root type of the `__counted_by` path, you can
just find that offset statically and subtract to get a pointer to the root
type. But of course that only works if it *is* uniquely allocated directly
within the root type, which it isn't going to be in the general case if the
root type is just some lexically-enclosing struct, which ties this back to the
other conversation.
Stepping back for a second, I'm surprised you need to do so much from scratch
for flexible arrays. Don't the other `-fbounds-safety` features already have
some logic where they recognize e.g. a load from a `__counted_by` field of
pointer type and then emit the count expression? How do those code paths solve
this problem?
https://github.com/llvm/llvm-project/pull/73730
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