[cfe-dev] Getting "wrong" ObjCMethodDecl-reference from ObjCMessageExpr

Hendrik vP variadic.template at googlemail.com
Sat May 5 14:12:18 PDT 2012

Sounds plausible, thank you!

2012/5/5 John McCall <rjmccall at apple.com>:
> On May 5, 2012, at 10:17 AM, Hendrik vP wrote:
>> while playing around with libClang and trying to extract some
>> statistics of objective-c-code, I encountered some strange behavior on
>> ObjCMessageExpressions.
>> ObjCMessageExpr-instances have a getMethodDecl-method, which I'm
>> expecting to return the _exact_ ObjCMethodDecl-instance if clang is
>> able to deduce it - or null, if clang has not the ability to do so.
> The compiler never has the ability to deduce the exact method that a
> message send goes to, because it's supported behavior to do things
> like replace methods at runtime or patch the class pointer or whatever.
> ObjCMessageExpr points to the method that the message send was
> type-checked against.  The specified behavior in the case of a message
> send to 'id' is to type-check against the first method with that selector
> that was declared in the file.  Finding a method to type-check against
> is important because many, many methods do not return a type
> compatible with 'id'.  Using the first method is also important because
> (IIRC) Cocoa manages to declare two methods with incompatible
> return types using the 'length' selector, and it's critical that we silently
> pick the one from NSString.
> John.

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