[LLVMdev] Assertion in the linker on Mac OS X

[Jacob Carlborg]

This post might be a bit off topic but I'm hoping there's someone here 
that can help me.

I'm working on implementing support for the Objective-C ABI in the D 
programing language. I've based my work on the work made by another 
developer a couple of years ago. Most of the code is already in place 
and I'm now trying to make sure everything works after the merging the 
latest changes from the D compiler.

The problem I have is when linking some code that calls an Objective-C 
method. As far as I understand the object file is supposed to contain a 
section __message_refs, in the __OBJC segment. This section contains 
pointers to C strings, which contain the names of the Objective-C 
selectors (methods). The C strings are stored in the __cstring __TEXT 
section and segment. As far as I can see the these sections looks to 
have the correct flags and contents.

The problem is I'm getting an assertion in the linker:

http://www.opensource.apple.com/source/ld64/ld64-134.9/src/ld/parsers/macho_relocatable_file.cpp

Line 5024, in Objc1ClassReferences<A>::targetCString. I'm pretty sure 
that the value of "fit->binding" should be 
"ld::Fixup::bindingByContentBound" but instead it is 
"ld::Fixup::bindingDirectlyBound". The definition of these enums are 
located here:

http://www.opensource.apple.com/source/ld64/ld64-134.9/src/ld/ld.hpp

Line 358, in Fixup::TargetBinding.

This is the result of "dumpobj", a tool shipped with the D compiler, on 
the D object file that fails to link:

http://pastebin.com/uPNZ8DpA

This is the dump of a corresponding Objective-C object file:

http://pastebin.com/NjbRRdZM

The following is a dump using a pre compiled alpha release of the D 
compiler that the developer I'm basing my work on released in 2011. This 
does not have this problem:

http://pastebin.com/rjjT1LBU

I'm running Mac OS X 10.8.3. All code is compiled as 32bit.

-- 
/Jacob Carlborg