[PATCH] Initial pass at API design for DebugInfo/PDB

Zachary Turner zturner at google.com
Tue Feb 3 15:52:18 PST 2015

Fair enough, it's not a huge deal either way.  I've made this and some of
the other suggested changes locally.

I'm a little bit more comfortable with this design I have now, especially
now that it works directly with llvm::dyn_cast<> and llvm::isa<>.  Anyone
have any major objections or concerns?  I will probably try to go in with
this sometime tomorrow if not.

On Tue Feb 03 2015 at 3:29:14 PM David Blaikie <dblaikie at gmail.com> wrote:

> On Tue, Feb 3, 2015 at 3:25 PM, Zachary Turner <zturner at google.com> wrote:
>> I was thinking it might still be useful for people who knew what they
>> were doing and who wanted to write some implementation-specific code to be
>> able to get at the native native interface.  Like in this case a raw COM
>> pointer.  In theory this shouldn't ever be necessary, but it's hard to say
>> without knowing anything about implementation strategies other than DIA how
>> much compatibility someone would be able to achieve, and if there ever
>> might be things that are only possible to implement in terms of one API but
>> not the other.  So I didn't want to prematurely remove the possibility to
>> get at the native interface, for example by writing
>> static_cast<DIASymbol*>(PDBSymbol::getRawSymbol())->someDIAOnlyMethod().
> I tend to err on the other side - we can always add more API if we find a
> use for it. No need to pay for things we're not using in the interim. But
> ultimately up to you.
> - David
>> On Tue Feb 03 2015 at 3:19:11 PM David Blaikie <dblaikie at gmail.com>
>> wrote:
>>> On Tue, Feb 3, 2015 at 3:11 PM, Zachary Turner <zturner at google.com>
>>> wrote:
>>>> ================
>>>> Comment at: include/llvm/DebugInfo/PDB/IPDBRawSymbol.h:193
>>>> @@ +192,3 @@
>>>> +  virtual bool isVirtualInheritance() const = 0;
>>>> +  virtual bool isVolatileType() const = 0;
>>>> +};
>>>> ----------------
>>>> dblaikie wrote:
>>>> > How're these functions going to communicate failure?
>>>> Undefined in theory, probably false in practice.  You shouldn't call
>>>> methods on the raw interface unless you know it's a valid method.
>>>> For the purposes of a dumper who wanted to detect unknown / unexpected
>>>> fields, that knowledge could all be encapsulated in the implementation of
>>>> the raw interface.  For example, you could have PDBSymbol::dump() which
>>>> calls RawSymbol->dump(), and that particular implementation can go to the
>>>> native API instead of calling the friendly accessors.
>>> Ah - that's a bit different from what I was thinking from our previous
>>> discussion.
>>> If it's undefined behavior, then it might be appropriate to hide
>>> PDBRawSymbol from users entirely - they might as well be casting down to
>>> the specific type and using those functions instead, perhaps? (I was
>>> thinking clients would be able to use PDBRawSymbol and just call all the
>>> functions and swallow the failures when they would call the wrong functions)
>>> - David
>>>> http://reviews.llvm.org/D7356
>>>>   http://reviews.llvm.org/settings/panel/emailpreferences/
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