BridgeSupport's type and type64

BridgeSupport describes the system's frameworks in .xml files. This is used by RubyCocoa to call C functions and understand C enums, constants and structs. It looks like this :
  <function name='NSRunAlertPanel' variadic='true'>
    <arg name='title' declared_type='NSString*' type='@'/>
    <arg printf_format='true' name='msgFormat' declared_type='NSString*' type='@'/>
    <arg name='defaultButton' declared_type='NSString*' type='@'/>
    <arg name='alternateButton' declared_type='NSString*' type='@'/>
    <arg name='otherButton' declared_type='NSString*' type='@'/>
    <retval declared_type='NSInteger' type='i' type64='q'/>

gen_bridge_metadata.rb analyzes the frameworks and outputs this description. type and type64 are in fact type encodings, straight from the compiler's @encode function !

To generate a .bridgesupport file, feed gen_bridge_metadata.rb a framework path and it will :

  • analyze the framework's header files
  • collect enum, constant, struct definitions
  • build dummy C files asking for type encodings (printf of the type's @encode output) and constant values
  • compile those dummy files
  • execute them then parse the output, yielding the compiler's type encodings of structs and functions plus constant values

Once done, the .bridgesupport file can be generated. All of this is done without the framework's sources — just by parsing its headers. Both hacky and elegant !

Sample log

BridgeSupport handling QuartzCore shows a log of gen_bridge_metadata.rb describing the frameworks.

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