aaron.ballman added inline comments.
================
Comment at: include/clang/Basic/DiagnosticSemaKinds.td:7417-7421
@@ -7416,4 +7416,7 @@
InGroup<Varargs>;
-def warn_va_start_of_reference_type_is_undefined : Warning<
- "'va_start' has undefined behavior with reference types">, InGroup<Varargs>;
+def warn_va_start_type_is_undefined : Warning<
+ "'va_start' has undefined behavior with "
+ "%select{types that undergo default argument promotion|reference types|"
+ "an object declared with the register storage class}0">,
+ InGroup<Varargs>;
def err_first_argument_to_va_arg_not_of_type_va_list : Error<
----------------
rsmith wrote:
> I'm not sure that
>
> 'va_start' has undefined behavior with an object declared with the
> register storage class
>
> is clear enough about what object it's talking about. Can you explicitly
> state that the problem is with the type of the parameter name passed to
> `va_start` here, somehow?
How about: "'va_start' has undefined behavior with a parameter declared with
the 'register' keyword"?
Then again, we could reword the entire diagnostic and I wouldn't be sad. I
notice that it's using the plural "types" already instead of the singular form,
for instance. How about:
"Passing %select{an object of reference type|an object that undergoes default
argument promotion|a parameter declared with the 'register' keyword}0 to
'va_start' is undefined behavior"
================
Comment at: lib/Sema/SemaChecking.cpp:2722
@@ -2720,2 +2721,3 @@
ParamLoc = PV->getLocation();
+ IsRegister = PV->getStorageClass() == SC_Register;
}
----------------
rsmith wrote:
> Where is this restriction specified? Does this only apply to C?
7.16.1.4p3:
If the parameter parmN is declared with the register storage class ... the
behavior is undefined.
I think this may only apply in C, actually, because [support.runtime]p3 does
not mention it in its description (even as far back as C++03). Whether that's
an explicit omission (to make va_start() more powerful than in C) or an
oversight is kind of moot since register was removed in C++17. Thoughts?
http://reviews.llvm.org/D19244
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