aaron.ballman added inline comments.
================
Comment at: test/Sema/riscv-interrupt-attr.c:23
+ // expected-note
{{repeated RISC-V 'interrupt' attribute is here}}
+__attribute__((interrupt("user"))) void foo8() {}
+__attribute__((interrupt("supervisor"))) void foo9() {}
----------------
apazos wrote:
> aaron.ballman wrote:
> > apazos wrote:
> > > aaron.ballman wrote:
> > > > aaron.ballman wrote:
> > > > > Do you intend for functions without a prototype to be accepted?
> > > > > foo8() can be passed an arbitrary number of arguments, which is a bit
> > > > > different than what I thought you wanted the semantic check to be.
> > > > This question remains outstanding.
> > > The checks are validating both function definitions and function
> > > prototypes like these:
> > > _attribute__((interrupt)) void foo1() {}
> > > __attribute__((interrupt)) void foo(void);
> > > Not sure what the confusion is.
> > Ah, now I see where the confusion is.
> >
> > In C, an empty parameter list declares a function without a prototype;
> > functions without prototypes can accept any number of arguments. To declare
> > a function that accepts no arguments, you must have a prototype for the
> > function and the parameter list is void. In C++, all functions are
> > prototyped and an empty parameter list is equivalent to a parameter list of
> > void. The word "prototype" doesn't mean "forward declaration". e.g.,
> > ```
> > // C code
> > void foo1(); // Declaration; no prototype; accepts any number of arguments.
> > void foo2() {} // Definition; no prototype; accepts any number of arguments.
> > void foo3(void); // Declaration; prototype; accepts no arguments.
> > void foo4(void) {} // Definition; prototype; accepts no arguments.
> >
> > foo2(1, 2, 3); // ok
> > foo4(1, 2, 3); // error
> > ```
> > Because a function without a prototype can accept any number of arguments,
> > I think you want to diagnose such a function signature.
> Thanks for clarifying.
>
> I checked GCC behavior and it is less strict. For the example below, it
> silently accepts the interrupt attribute.
>
> extern int foo2();
> __attribute__((interrupt)) void foo();
> void foo() {
> foo2();
> }
>
> while in LLVM we would be rejecting with the message:
> RISC-V 'interrupt' attribute only applies to functions that have no
> parameters.
>
> I find the reuse of the message confusing.
>
> If we want stricter rule then we probably also need a specific message for
> the missing prototype.
>
> I checked GCC behavior and it is less strict. For the example below, it
> silently accepts the interrupt attribute.
Does it drop the attribute?
> If we want stricter rule then we probably also need a specific message for
> the missing prototype.
If GCC silently drops the attribute in this case then we definitely want a more
strict rule. We already have a good diagnostic for this:
`warn_attribute_wrong_decl_type` with the expected type diagnostic index being
`ExpectedFunctionWithProtoType`.
https://reviews.llvm.org/D48412
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