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

David Blaikie dblaikie at gmail.com
Tue Feb 3 15:29:13 PST 2015

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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