tbaeder added inline comments.
================
Comment at: clang/lib/AST/ExprConstant.cpp:12951-12954
+ // ObjC's @encode()
+ if (isa<ObjCEncodeExpr>(E->getLHS()->IgnoreParenImpCasts()) ||
+ isa<ObjCEncodeExpr>(E->getRHS()->IgnoreParenImpCasts()))
return Error(E);
----------------
tahonermann wrote:
> tbaeder wrote:
> > tahonermann wrote:
> > > A comment to explain this change would be helpful. It isn't intuitive
> > > (for me anyway) why Objective-C's `@encode` would require special
> > > handling here. Was this needed to avoid a test failure?
> > In `../clang/test/CodeGenObjC/encode-test-4.m`:
> >
> > ```
> > int a(void) {
> > return @encode(int) == @encode(int) &&
> > @encode(Color) == @encode(long) &&
> > @encode(PrintColor) == @encode(int);
> > }
> > ```
> >
> > The comparisons need to be rejected here and are folded to a `1` later on,
> > it seems. Letting the comparison happen will lead to a `0`.
> Apologies, I meant it would be helpful to add a comment to the code :)
>
> I think `@encode(...)` expressions should be treated the same as string
> literals; the former is lowered to the latter; both contribute to the string
> table.
You mean the special case for them here should go away?
I've tracked this down to `CodeGenFunction::ConstantFoldsToSimpleInteger()`.
Without this special case for endcode expressions, we will return `true` here
and fold the comparison to `false`, so we will just emit that.
This is a funny case though, which also exists in C++. With this patch, `"a" ==
"a"` evaluates to `true`, as one would expect.
However, `"a" == "a" && "b" == "b"` will evaluate to `false`.
That's pretty wrong so I think the patch needs more work.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D137826/new/
https://reviews.llvm.org/D137826
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