nicholas marked 2 inline comments as done.
================
Comment at: lib/Sema/SemaInit.cpp:3514-3518
@@ +3513,7 @@
+static void CheckForNullPointerDereference(Sema &S, const Expr *E) {
+ // Check to see if we are dereferencing a null pointer. If so,
+ // and if not volatile-qualified, this is undefined behavior that the
+ // optimizer will delete, so warn about it. People sometimes try to use this
+ // to get a deterministic trap and are surprised by clang's behavior. This
+ // only handles the pattern "*null", which is a very syntactic check.
+ if (const UnaryOperator *UO = dyn_cast<UnaryOperator>(E->IgnoreParenCasts()))
----------------
rsmith wrote:
> This comment doesn't make sense for this case. Binding a reference to a
> dereferenced null pointer isn't something that people would expect to trap.
> But the idea is the same: we might delete people's code and they're probably
> not expecting that.
We don't delete it, generally we "create a null reference" which is exactly
what some programmers expect, when they think that references are just
syntactically different pointers.
================
Comment at: lib/Sema/SemaInit.cpp:3519-3522
@@ +3518,6 @@
+ // only handles the pattern "*null", which is a very syntactic check.
+ if (const UnaryOperator *UO = dyn_cast<UnaryOperator>(E->IgnoreParenCasts()))
+ if (UO->getOpcode() == UO_Deref &&
+ UO->getSubExpr()->IgnoreParenCasts()->
+ isNullPointerConstant(S.Context, Expr::NPC_ValueDependentIsNotNull)
&&
+ !UO->getType().isVolatileQualified()) {
----------------
rsmith wrote:
> It seems -- borderline -- worth factoring out these four lines between here
> and SemaExpr. Maybe `isProvablyEmptyLvalue` or similar, if you feel inclined
> to do so?
I'll pass. Initially I thought the two CheckForNullPointerDereference functions
might be the same but for a diag::ID argument, but they're growing more and
more different.
As for `isProvablyEmptyLvalue` we would still need to get the UO for the
diagnostic anyways.
http://reviews.llvm.org/D19851
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