rsmith added inline comments.
================
Comment at: lib/Sema/SemaChecking.cpp:4089-4090
@@ +4088,4 @@
+ if (BinOp->isAdditiveOp()) {
+ bool LIsInt = BinOp->getLHS()->EvaluateAsInt(LResult, S.Context);
+ bool RIsInt = BinOp->getRHS()->EvaluateAsInt(RResult, S.Context);
+
----------------
meikeb wrote:
> rsmith wrote:
> > What happens if one of these expressions is value-dependent? The evaluator
> > can crash or assert if given a value-dependent expression. If we don't
> > defer these checks in dependent contexts, you'll need to handle that
> > possibility somehow.
> >
> > Example:
> >
> > template<int N> void f(const char *p) {
> > printf("blah blah %s" + N, p);
> > }
> I think I don't understand what you are trying to tell me. Especially the
> example you provided does just fine and behaves as I expected. As far as I
> followed EvaluateAsInt it does not assert but returns false if we don't get a
> constexpr here. We warn under -Wformat-nonliteral for value-dependent string
> literals.
>
> Could you explain this more or provide an example that triggers an assert or
> explain what behavior is wrong regarding the provided example? Thanks!
We should not warn for that example, since (for instance) calling `f<0>` is
fine (we should warn for `f<11>`, though, since it has no format specifiers).
While `EvaluateAsInt` happens to not assert for that particular value-dependent
input, it does assert for some other value-dependent cases. It's not easy for
me to find you such a case, because Clang is currently careful to never call
this function on a value-dependent expression, but perhaps this will trigger an
assert:
struct S { constexpr S(int n) : n(n) {} int n; };
template<int N> void f(const char *p) {
printf("blah blah %s" + S(N).n, p);
}
https://reviews.llvm.org/D23820
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