Open Radar

 
Summary:
Invoking with NSInvocation a method returning a double (or CGFloat) value on an arm64 device returns 0 instead of the result returned by the method.

Steps to Reproduce:
1. With Xcode create an empty application
2. In the AppDelegate class, set the code as in the attached file CDVAppDelegate.m:
- define a simple method getAFloat as:

     - (CGFloat) getAFloat {
         return 1.0;
     }

 - in method application:didFinishLaunchingWithOptions: add the following code

    SEL methodSelector = @selector(getAFloat);
    NSMethodSignature* methodSignature = [self methodSignatureForSelector:methodSelector];
    NSInvocation* invocation = [NSInvocation invocationWithMethodSignature:methodSignature];
    
    [invocation setTarget:self];
    [invocation setSelector:methodSelector];
    [invocation invoke];
    
    CGFloat returnValue = 0.0;
    [invocation getReturnValue:&returnValue];
    
    NSLog(@"Invocation return value: %f; getAFloat return value: %f", (double)returnValue, [self getAFloat]);

3. run the application


Expected Results:
The app log should display:
Invocation return value: 1.000000; getAFloat return value: 1.000000

Actual Results:
The app log actually displays:
Invocation return value: 0.000000; getAFloat return value: 1.000000

Version:
iOS version: 7.0.4 (11B554a)

Notes:
The problem may be located in the class NSMethodSignature, as displaying the description of variable methodSignature in the sample code prints an incorrect result offset:

(lldb) po methodSignature
<NSMethodSignature: 0x170079640>
    number of arguments = 2
    frame size = 224
    is special struct return? NO
    return value: -------- -------- -------- --------
        type encoding (d) 'd'
        flags {isFloat}
        modifiers {}
        frame {offset = 80, offset adjust = 248, size = 16, size adjust = 0}
        memory {offset = 0, size = 8}
    argument 0: -------- -------- -------- --------
        type encoding (@) '@'
        flags {isObject}
        modifiers {}
        frame {offset = 0, offset adjust = 0, size = 8, size adjust = 0}
        memory {offset = 0, size = 8}
    argument 1: -------- -------- -------- --------
        type encoding (:) ':'
        flags {}
        modifiers {}
        frame {offset = 8, offset adjust = 0, size = 8, size adjust = 0}
     



Configuration:
Xcode Version 5.0.2 (5A3005)
device: iPad Air (Model A1475)

-------------------------------

Additional note - 16-Nov-2013 06:07 PM

It seems confirmed that the issue lays in the NSSignature class:
When running the program in the simulator in mode "iPad retina (64 bits), the description of the methodSignature instance gives a correct offset for the return value:

po methodSignature
<NSMethodSignature: 0x109062040>
    number of arguments = 2
    frame size = 224
    is special struct return? NO
    return value: -------- -------- -------- --------
        type encoding (d) 'd'
        flags {isFloat}
        modifiers {}
        frame {offset = 16, offset adjust = 0, size = 16, size adjust = -8}
        memory {offset = 0, size = 8}
    argument 0: -------- -------- -------- --------
        type encoding (@) '@'
        flags {isObject}
        modifiers {}
        frame {offset = 0, offset adjust = 0, size = 8, size adjust = 0}
        memory {offset = 0, size = 8}
    argument 1: -------- -------- -------- --------
        type encoding (:) ':'
        flags {}
        modifiers {}
        frame {offset = 8, offset adjust = 0, size = 8, size adjust = 0}
        memory {offset = 0, size = 8}