[cfe-commits] r141261 - in /cfe/trunk: lib/CodeGen/CGDebugInfo.cpp test/CodeGenObjC/debug-info-crash-2.m

[jahanian]

On Oct 6, 2011, at 11:03 AM, Eric Christopher wrote:

>> 
>> Here is the meta-data to show that synthesized variable is no different than none-synthesized.
>> I used your test case but added a user declared ivar "IAddedThisIvar" to show this point.
>> 
>> l_OBJC_$_INSTANCE_VARIABLES_Foo:
>>       .long   32                      ## 0x20
>>       .long   2                       ## 0x2
>>       .quad   _OBJC_IVAR_$_Foo.IAddedThisIvar
>>       .quad   L_OBJC_METH_VAR_NAME_4
>>       .quad   L_OBJC_METH_VAR_TYPE_5
>>       .long   3                       ## 0x3
>>       .long   8                       ## 0x8
>>       .quad   _OBJC_IVAR_$_Foo._window
>>       .quad   L_OBJC_METH_VAR_NAME_6
>>       .quad   L_OBJC_METH_VAR_TYPE_5
>>       .long   3                       ## 0x3
>>       .long   8                       ## 0x8
>> 
> 
> Adding a variable makes the problem go away :)
> 
> That said, it appears that the order that we're processing the implementations matters here as well and that there's no variable in Foo__. If we process the implementation of Foo before Foo__ we won't show the problem. My current thought is that we're trying to lay out Foo as part of processing the type of Foo__ and since we haven't laid out the implementation of Foo we don't know about the synthesize yet and think there aren't any variables.

Order of implementation is their lexical order. In your example, Foo__'s meta-data is generated with no ivar, followed by metadata Foo
with two ivars. Foo__'s metadata only contains symbols for Foo's class meta data. It will not and cannot generate Foo's meta data on its own.

> 
> An earlier patch I had worked this up by looking up the implementation decl and using that as part of the layout request, but John didn't think that was correct but rather that we shouldn't be looking up the size in the non-fragile ABI.
> 

Offset that you see is the offset as seen by the compiler. It is not necessarily offset of the ivar in the object. Final offset is determined by the runtime.
In any case: 1) there is no distinction between user-declared ivar and those synthesized when it comes to debug info. 2) Your logic should
not depend on order of implementations and that both be available; as this is not the case in most situations.

- fariborz



> Thoughts?
> 
> -eric