[PATCH] Support native mach-o names in MachOFormat.h

[Nick Kledzik]

Chip,

I talked to Michael Spencer and Jim Grosbach off-list and they both think switching Support/MachO.h to use the documented mach-o names is a good idea.   You said you’ve been sitting on the patch a while.  What has been holding you back from getting the patch in?  I’d like it to go in, to help me with my lld work.

-Nick

On Aug 19, 2013, at 3:54 PM, Charles Davis <cdavis5x at gmail.com> wrote:
> On Aug 19, 2013, at 4:22 PM, Nick Kledzik wrote:
> 
>> Wow, that was fast Charles!
> Yeah, I've been sitting on those patches for a while.
>> 
>> I did not know that Support/MachO.h even existed!
> Outside of LLDB, hardly anyone does. They added it, and AFAIK they're the only ones that use it right now. (These patches will obviously change that.)
>>  Why does Object/MachOFormat.h and it both define the same things differently?
> I don't know, and that's why I wanted to get rid of one. I suspect that whoever added Object/MachOFormat.h probably didn't know about Support/MachO.h either.
>>   There was some recent changes to ELF headers to layer them.  Is there something analogous we need to do for mach-o?
> We used to do something similar--we had the MachOObject class that does about the same thing as the ELFFile class (i.e. it was a low-level interface to a Mach Object), except without the heavy template meta-programming. MachOObjectFile was then just a thin wrapper around it, just as ELFObjectFile is now just a wrapper around ELFFile. But Rafael Espíndola got rid of that a while back, saying something about the InMemoryStruct template not working right. (He also wanted to add the kind of template meta-programming to Mach-O that ELF was using for its structs, but that got shot down.)
> 
> Chip
> 
>> 
>> -Nick
>> 
>> On Aug 19, 2013, at 3:14 PM, Charles Davis <cdavis5x at gmail.com> wrote:
>>> On Aug 19, 2013, at 4:02 PM, Eric Christopher wrote:
>>> 
>>>> Probably wouldn't take much to fix up all the name uses and leave out
>>>> the conditional?
>>> I have two patches; one does what Nick's patch does, but to <llvm/Support/MachO.h>, and also updates everything using it in LLVM to use the new names, and one that strips out the now-redundant <llvm/Object/MachOFormat.h> header and changes everything using *that* to use the new names.
>>> 
>>> Chip
>>> <0001-Support-MachO-Add-a-bunch-of-defines.patch><0002-Move-everything-depending-on-Object-MachOFormat.h-ov.patch>
>>> 
>>>> 
>>>> -eric
>>>> 
>>>> On Mon, Aug 19, 2013 at 2:57 PM, Nick Kledzik <kledzik at apple.com> wrote:
>>>>> [+patch]
>>>>> 
>>>>> include/llvm/Object/MachOFormat.h is odd in that it makes up new names for the public mach-o format structs and constants (e.g. it defines LCT_Segment instead of LC_SEGMENT). LLVM does not handle ELF this way.  LLVM defines SHT_PROGBITS just like the standard ELF header (although llvm puts them into a namespace).  This current set up makes it hard to reconcile the public mach-o documentation with llvm source code.
>>>>> 
>>>>> This patch adds all the standard mach-o names for structs and constants in the llvm::object::mach_o namespace.  All the existing names remain, but I put them inside #ifndef LLVM_NO_OLD_MACH_O_NAMES, so that if someone wanted to switch to the standard names they could define LLVM_NO_OLD_MACH_O_NAMES, do a full build, and update whatever failures are seen.
>>>>> 
>>>>> This issue came up during a code review of lld, as to why lld was defining it own mach-o constants instead of using the ones in llvm.
>>>>> 
>>>>> -Nick
>>>>> 
>>>>> 
>>>>> 
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>>>> 
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