[LLVMdev] Removing std::vector from APIs (was Re: Mutating the elements of a ConstantArray)

Chris Lattner clattner at apple.com
Thu May 14 10:08:41 PDT 2009

On May 14, 2009, at 4:56 AM, Jay Foad wrote:

> 2009/4/1 Chris Lattner <clattner at apple.com>:
>> As far API design goes, we're in a mixed state.  I'd strongly prefer
>> to get rid of std::vector from the various interfaces, f.e.  
>> creating a
>> constant array currently requires passing in an std::vector.  For
>> these sorts of interfaces, we should migrate to passing in a  
>> "Constant
>> *const* / unsigned" pair.  This allows use with a C array, a
>> SmallVector, std::vector, or any other container with sequential
>> storage.
> I've made a start on this for the constructors of StructType and
> FunctionType. I've attached the patch so far, which is just enough to
> build lib/VMCore/. Before I continue with it:


> 1. Is this still the way you want to go?


> 2. Do you care about breaking out-of-tree code that creates struct or
> function types? I'm happy to convert cfe and llvm-gcc myself.

Nope, we expect people with out of tree code to update themselves.

> 3. Are there any logistical problems with committing a wide-reaching
> patch like this?

I don't think so.

> 3. Any comments on the patch itself?

The one major thing to be aware of is that it isn't safe to use &V[0]  
when V is an empty std::vector (though it is safe for smallvector).   
When converting code, just be careful so that this doesn't break {} or  

One minor thing is that StructType::get(NULL, 0) looks somewhat  
strange to me.  How about adding a zero-argument version of "get" that  
returns the empty struct?  That would allow code to use  

Thanks for working on this Jay!

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