Because the name of a direct method must be agreed upon by the caller
and the implementation, certain bad practices that one can get away with
when using dynamism are fatal with direct methods.
To avoid really weird and unscruttable linker error, tighten the
front-end error reporting.
Rule 1:
Direct methods can only have at most one declaration in an @interface
container. Any redeclaration is strictly forbidden.
Today some amount of redeclaration is tolerated between the main
interface and categories for dynamic methods, but we can't have that.
Rule 2:
Direct method implementations can only be declared in a matching
@interface container: when implemented in the primary @implementation
then the declaration must be in the primary @interface or an
extension, and when implemented in a category, the declaration must be
in the @interface for the same category.
Also fix another issue with ObjCMethod::getCanonicalDecl(): when an
implementation lives in the primary @interface, then its canonical
declaration can be in any extension, even when it's not an accessor.
Add Sema tests to cover the new errors, and CG tests to beef up testing
around function names for categories and extensions.
Radar-Id: <rdar://problem/58054563>
Differential Revision: https://reviews.llvm.org/D71694
ObjCMethodDecl::getCanonicalDecl() for re-declared readwrite properties,
only looks in the ObjCInterface for the declaration of the setter
method, which it won't find.
When the method is a property accessor, we must look in extensions for a
possible redeclaration.
Radar-Id: rdar://problem/57991337
Differential Revision: https://reviews.llvm.org/D71588
This commit sets the Self and Imp declarations for ObjC method declarations,
in addition to the definitions. It also fixes
a bunch of code in clang that had wrong assumptions about when getSelfDecl() would be set:
- CGDebugInfo::getObjCMethodName and AnalysisConsumer::getFunctionName would assume that it was
set for method declarations part of a protocol, which they never were,
and that self would be a Class type, which it isn't as it is id for a protocol.
Also use the Canonical Decl to index the set of Direct methods so that
when calls and implementations interleave, the same llvm::Function is
used and the same symbol name emitted.
Radar-Id: rdar://problem/57661767
Patch by: Pierre Habouzit
Differential Revision: https://reviews.llvm.org/D71091
__attribute__((objc_direct)) is an attribute on methods declaration, and
__attribute__((objc_direct_members)) on implementation, categories or
extensions.
A `direct` property specifier is added (@property(direct) type name)
These attributes / specifiers cause the method to have no associated
Objective-C metadata (for the property or the method itself), and the
calling convention to be a direct C function call.
The symbol for the method has enforced hidden visibility and such direct
calls are hence unreachable cross image. An explicit C function must be
made if so desired to wrap them.
The implicit `self` and `_cmd` arguments are preserved, however to
maintain compatibility with the usual `objc_msgSend` semantics,
3 fundamental precautions are taken:
1) for instance methods, `self` is nil-checked. On arm64 backends this
typically adds a single instruction (cbz x0, <closest-ret>) to the
codegen, for the vast majority of the cases when the return type is a
scalar.
2) for class methods, because the class may not be realized/initialized
yet, a call to `[self self]` is emitted. When the proper deployment
target is used, this is optimized to `objc_opt_self(self)`.
However, long term we might want to emit something better that the
optimizer can reason about. When inlining kicks in, these calls
aren't optimized away as the optimizer has no idea that a single call
is really necessary.
3) the calling convention for the `_cmd` argument is changed: the caller
leaves the second argument to the call undefined, and the selector is
loaded inside the body when it's referenced only.
As far as error reporting goes, the compiler refuses:
- making any overloads direct,
- making an overload of a direct method,
- implementations marked as direct when the declaration in the
interface isn't (the other way around is allowed, as the direct
attribute is inherited from the declaration),
- marking methods required for protocol conformance as direct,
- messaging an unqualified `id` with a direct method,
- forming any @selector() expression with only direct selectors.
As warnings:
- any inconsistency of direct-related calling convention when
@selector() or messaging is used,
- forming any @selector() expression with a possibly direct selector.
Lastly an `objc_direct_members` attribute is added that can decorate
`@implementation` blocks and causes methods only declared there (and in
no `@interface`) to be automatically direct. When decorating an
`@interface` then all methods and properties declared in this block are
marked direct.
Radar-ID: rdar://problem/2684889
Differential Revision: https://reviews.llvm.org/D69991
Reviewed-By: John McCall
Erik Pilkington