[cfe-dev] GNU runtime non-fragile ABI and cleanup

[David Chisnall]

On 30 Aug 2009, at 18:46, Fariborz Jahanian wrote:

> Did you want this in your patch?

No, this happened when I ran the test suite; there appears to be a bug  
in a pipe somewhere, because the test ran fine the first time then  
failed the second time because the file was full of nonsense.  I  
thought I'd reverted it (I had, but apparently after I created the  
diff).

> Few comments:
>
> +
> +    ObjCConstantStringClass = "NXConstantString";
>
> This is specific to Gnu runtime and initialization should happen for  
> when in Gnu-specific runtime mode.

I've made this change for now, but it breaks layering because the  
default to NXConstantString is for GCC compatibility (should be  
NSConstantString on the NeXT runtime, NSCFString for the NeXT runtime  
when -fconstant-cfstrings is provided or the target is Darwin) and so  
should be set in the driver, not in CodeGen.

> -OPTION("-pthread", pthread, Flag, INVALID, INVALID, "", 0, 0, 0)
> +OPTION("-pthread", pthread, Flag, INVALID, INVALID, "q", 0, 0, 0)
>
> Unrelated to this patch. Please provide a separate patch for this  
> (and a test case) if you want it.

Reverted; this was a quick hack from an earlier diff, I think someone  
else fixed this in the correct way.

> @@ -818,6 +824,9 @@
>   else if (GNURuntime)
>     Options.NeXTRuntime = 0;
>
> +  if (!ObjCConstantStringClass.empty())
> +    Options.ObjCConstantStringClass = ObjCConstantStringClass.c_str 
> ();
> +
>
> This should happen when in GNURuntime. For other runtimes please  
> issue a warning that option is not supported.

This should also be supported for the NeXT runtime - this option was  
created by NeXT for NeXTSTEP compatibility in OPENSTEP, when the  
constant string class was renamed from NXConstantString (NeXT  
namespace, used on NeXTSTEP) to NSConstantString (NeXT-Sun namespace  
used on OpenStep implementations including OPENSTEP).  From the Apple  
GCC docs:

>> -fconstant-string-class=class-name
>> Use class-name as the name of the class to instantiate for each  
>> literal string specified with the syntax @"...". The default class  
>> name is NXConstantString if the GNU runtime is being used, and  
>> NSConstantString if the NeXT runtime is being used (see below). The  
>> -fconstant-cfstrings option, if also present, will override the - 
>> fconstant-string-class setting and cause @"..." literals to be laid  
>> out as constant CoreFoundation strings.

There are other subtle details in the semantics of the NeXT-compatible  
implementation of this, which I will leave to you.

> Please provide a test case for this patch.

I've modified CodeGenObjC/constant-strings.m to test that this works.

Any other comments?

David