[PATCH] D93822: [clang][Sema] Add diagnostics for implicit widening of multiplication result

[Roman Lebedev via Phabricator via cfe-commits]

lebedev.ri added inline comments.


================
Comment at: clang/test/Sema/implicit-widening-of-pointer-offset-in-array-subscript-expression.c:24
+void t1(char *base, int a, int b) {
+  // FIXME: test `[a * b]base` pattern?
+}
----------------
dblaikie wrote:
> lebedev.ri wrote:
> > dblaikie wrote:
> > > lebedev.ri wrote:
> > > > dblaikie wrote:
> > > > > Question is unclear - is there uncertainty about whether this should be tested? Or is this a false negative case? In which case I'd probably include the test showing no diagnostic and mention it could be fixed/improved?
> > > > I may be misremembering things, but IIRC `a[b]` and `b[a]` is the same thing,
> > > > but i'm not sure how to exercise the second spelling.
> > > > I.e. i'm just not sure how to write a test for it.
> > > > I may be misremembering things, but IIRC a[b] and b[a] is the same thing,
> > > Yep, that's the case - `a[b]` where one of them is a pointer and teh other is an integer, is equivalent to `*(a + b)`, so that means it's the same as `b[a]`.
> > > 
> > > I guess you'd write it the same as t0, but with the expressions reversed? `return *(a * b)[base];`
> > That's what i tried, and it does't work - https://godbolt.org/z/as4vP4
> Sorry, my mistake - the `*` was wrong. This works: https://godbolt.org/z/j9jqx3
Aha, thanks.


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  https://reviews.llvm.org/D93822/new/

https://reviews.llvm.org/D93822