ahatanak added inline comments.
================
Comment at: clang/lib/Sema/SemaExpr.cpp:5917
if (auto *BE = dyn_cast<BlockExpr>(Arg->IgnoreParenNoopCasts(Context)))
BE->getBlockDecl()->setDoesNotEscape();
----------------
rjmccall wrote:
> ahatanak wrote:
> > rjmccall wrote:
> > > We need to be checking that the parameter type is a block pointer type.
> > > A parameter of a type like `id` or `void*` does not have the enhanced
> > > semantics of `noescape` for blocks.
> > >
> > > The inevitable weird C++ test case is:
> > >
> > > ```
> > > struct NoescapeCtor {
> > > NoescapeCtor(__attribute__((noescape)) void (^)());
> > > };
> > > struct EscapeCtor {
> > > EscapeCtor(void (^)());
> > > };
> > >
> > > void helper1(NoescapeCtor a);
> > > void test1() { helper1(^{}); } // <- should be noescape
> > >
> > > void helper2(NoescapeCtor &&a);
> > > void test2() { helper2(^{}); } // <- should be noescape
> > >
> > > void helper3(__attribute__((noescape)) EscapeCtor &&a);
> > > void test3() { helper3(^{}); } // <- should not be noescape
> > > ```
> > >
> > > You should probably also test that calls to function templates behave
> > > according to the instantiated type of the parameter. I expect that that
> > > should just fall out from this implementation, which I think only
> > > triggers on non-dependent calls.
> > I understand why the blocks should or shouldn't be `noescape` in the C++
> > example, but I'm not sure I understand the comment about `id` and `void*`.
> >
> > Do you mean the `DoesNotEscape` bit shouldn't be set in the following
> > example?
> >
> > ```
> > void helper(__attribute__((noescape)) id);
> >
> > void test() {
> > S s;
> > helper(^{ (void)s; });
> > }
> > ```
> The [noescape
> documentation](https://clang.llvm.org/docs/AttributeReference.html#id357)
> says:
>
> > Additionally, when the parameter is a block pointer, the same restriction
> > applies to copies of the block.
>
> That's the restriction that makes the `noescape` block optimization sound,
> and it doesn't apply when the parameter does not have block pointer type. So
> yes, `DoesNotEscape` shouldn't be set in that example.
Ah, I see.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D101097/new/
https://reviews.llvm.org/D101097
_______________________________________________
cfe-commits mailing list
cfe-commits@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
