gulfem marked an inline comment as done.
gulfem added inline comments.
================
Comment at: clang/include/clang/Basic/Attr.td:1435
+ let Spellings = [GCC<"leaf">];
+ let Subjects = SubjectList<[Function]>;
+ let Documentation = [Undocumented];
----------------
aaron.ballman wrote:
> gulfem wrote:
> > aaron.ballman wrote:
> > > gulfem wrote:
> > > > aaron.ballman wrote:
> > > > > gulfem wrote:
> > > > > > aaron.ballman wrote:
> > > > > > > Should this attribute also be supported on things like ObjC
> > > > > > > method decls or other function-like interfaces?
> > > > > > Do I need to do anything else to support this attribute in
> > > > > > Objective-C as well?
> > > > > > I think we should support it in all the C languages family.
> > > > > >I think we should support it in all the C languages family.
> > > > >
> > > > > That's already happening automatically -- there's a C and C++
> > > > > spelling available for it and the attribute doesn't specify that it
> > > > > requires a particular language mode or target.
> > > > >
> > > > > > Do I need to do anything else to support this attribute in
> > > > > > Objective-C as well?
> > > > > You can add multiple subjects to the list here, so you can have this
> > > > > apply to `Function, ObjCMethod` for both of those. Another one to
> > > > > consider is whether this attribute can be written on a block
> > > > > declaration (like a lambda, but with different syntax). Beyond that,
> > > > > it's mostly just documentation, devising the test cases to ensure the
> > > > > ObjC functionality behaves as expected, possibly some codegen
> > > > > changes, etc.
> > > > AFAIK, users can specify function attributes in lambda expressions.
> > > > Lambda functions can only be accessed/called by the functions in the
> > > > same translation unit, right?
> > > > Leaf attribute does not have any effect on the functions that are
> > > > defined in the same translation unit.
> > > > For this reason, I'm thinking that leaf attribute would not have any
> > > > effect if they are used in lambda expressions.
> > > > Do you agree with me?
> > > > AFAIK, users can specify function attributes in lambda expressions.
> > >
> > > I always forget that you can do that for declaration attributes using
> > > GNU-style syntax...
> > >
> > > > Lambda functions can only be accessed/called by the functions in the
> > > > same translation unit, right?
> > >
> > > Not necessarily, you could pass one across TU boundaries like a function
> > > pointer, for instance. e.g.,
> > > ```
> > > // TU1.cpp
> > > void foo() {
> > > auto l = []() { ... };
> > > bar(l);
> > > }
> > >
> > > // TU2.cpp
> > > void bar(auto func) {
> > > func();
> > > }
> > > ```
> > > Not necessarily, you could pass one across TU boundaries like a function
> > > pointer, for instance. e.g.,
> > As I mentioned before, leaf attribute is specifically intended for library
> > functions and I think all the existing usage of leaf attribute is in the
> > library function declarations. For this reason, I think we do not need to
> > support them for lambdas. Is that reasonable?
> >
> > For this reason, I think we do not need to support them for lambdas. Is
> > that reasonable?
>
> Is this considered a library function?
>
> ```
> struct S {
> void f(); // Is this a library function?
> void operator()(); // How about this?
> };
> ```
> If the answer is "no", then I think we only need to support `FunctionDecl`
> and nothing else (not even `ObjCMethodDecl`, which is like a member function
> for ObjC). If the answer is "yes", then it's not clear to me whether lambdas
> should or should not be supported given that the attribute on the lambda
> expression is attached to the function call operator for the lambda
> declaration.
> If the answer is "no", then I think we only need to support `FunctionDecl`
> and nothing else (not even `ObjCMethodDecl`, which is like a member function
> for ObjC). If the answer is "yes", then it's not clear to me whether lambdas
> should or should not be supported given that the attribute on the lambda
> expression is attached to the function call operator for the lambda
> declaration.
I see your point @aaron.ballman. I would say the second one is not really a
library function.
@jdoerfert also suggested to allow leaf attribute only on declarations.
I can add FunctionDecl, so we only allow leaf attribute on function
declarations, not on function definitions or member functions.
Does that sound good to both of you?
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D90275/new/
https://reviews.llvm.org/D90275
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