[MacRuby] #1439: Invalid offsets in structs

[MacRuby]

#1439: Invalid offsets in structs
-------------------------------+--------------------------------------------
 Reporter:  fjolnir@…          |       Owner:  lsansonetti@…        
     Type:  defect             |      Status:  new                  
 Priority:  critical           |   Milestone:                       
Component:  MacRuby            |    Keywords:  float struct offset  
-------------------------------+--------------------------------------------
 I expose a struct  from my framework (definition below). However when
 accessing/allocating it from ruby it seems the offsets are off by 4 bytes
 (as if macruby think it's supposed to be a double)

 Definition:
 {{{
 #ifndef __SCRIPTINGBRIDGE__
 union _vec3_t {
         float f[3];
         struct { float x; float y; float z; };
         struct { float r; float g; float b; };
         struct { vec2_t xy; float andY; };
 };
 typedef union _vec3_t vec3_t;
 #else
 typedef struct _vec3_t { float x; float y; float z; } vec3_t; //
 Bridgesupport ignores unions with anonymous structs apparently
 #endif
 }}}
 Example output:
 {{{
 irb(main):001:0> framework "./GLMath.framework"
 => true
 irb(main):002:0> v1 = vec3_create(1,2,3)
 => #<vec3_t x=1.0 y=3.0 z=NaN>
 irb(main):003:0> v2 = v1.class.new(4,5,6)
 => #<vec3_t x=4.0 y=5.0 z=6.0>
 irb(main):004:0> printVec3(v1)
 0x676f1310 - 0x676f1314 - 0x676f1318
 Vec3: [1.00, 0.00, 3.00]
 => nil
 irb(main):005:0> printVec3(v2)
 0x676f1310 - 0x676f1314 - 0x676f1318
 Vec3: [4.00, 0.00, 5.00]
 => nil
 }}}
 in the above example, vec3_create & printVec3 are C functions, shared
 using the scripting bridge.
 So when the struct is allocated from the c side, ruby only sees the first
 & last items, and the last item is on the offset of the second.
 when I then pass it to printVec3,  it gets the first and last items only
 (last item taken from the place of the second item, => offsets are double
 what they should be).
 then when I allocate it using FFI in ruby, it's correcly read from the
 ruby side, but when I pass it to a c function, it gets the first item in
 the correct place, then the second item in the place of the last.

 The type definitions in my bridge support  file are:
 {{{
 <struct name='vec3_t'
 type='{_vec3_t="x"f"y"f"z"f}'/>
 <function name='vec3_create' inline='true'>
 <arg type='f'/>
 <arg type='f'/>
 <arg type='f'/>
 <retval type='{_vec3_t=fff}'/>
 </function>
 <function name='printVec3'>
 <arg type='{_vec3_t=fff}'/>
 </function>
 }}}

 I really want to use MacRuby for my project, but this is kind of a deal
 breaker for me. I've tried using different packing attributes and all
 sorts of things, but nothing seems to fix this.

 Can I somehow make my bridgesupport file specify the correct offsets to
 work around this?

-- 
Ticket URL: <http://www.macruby.org/trac/ticket/1439>
MacRuby <http://macruby.org/>