On Apr 29, 2009, at 1:30 PM, Sebastian Redl wrote:
> Douglas Gregor wrote:
>> On Apr 29, 2009, at 10:30 AM, Sebastian Redl wrote:
>>
>>> Author: cornedbee
>>> Date: Wed Apr 29 12:30:04 2009
>>> New Revision: 70389
>>>
>>> URL: http://llvm.org/viewvc/llvm-project?rev=70389&view=rev
>>> Log:
>>> Have the parser communicate the exception specification to the
>>> action.
>>
>> Oooh, I have a feeling you're going to run into C++'s "shadow type
>> system" very soon :)
>>
> What? Are you talking about compatibility of functions and function
> pointers with exception specifications?
Yes. Exception specifications act like they are part of a function
pointer type in some cases, but from the type-identity perspective
they are not part of the function type.
>>>
>>> + // FIXME: Does an empty vector ever allocate? Exception
>>> specifications are
>>> + // extremely rare, so we want something like a
>>> SmallVector<TypeTy*, 0>. :-)
>>> + std::vector<TypeTy*> Exceptions;
>>
>> I've never seen an std::vector that allocates. Now, it might be worth
>> using a SmallVector<TypeTy*, 4>, just so that a one- or two-exception
>> exception specification doesn't need to allocate. Besides, stack
>> space
>> is cheap :)
> How often are non-empty exception specifications really used in
> real-world code? As far as I know, everyone avoids them. They're
> ignored
> by MSVC completely, and are a performance pessimization in exchange
> for
> an inadequate exception translation mechanism everywhere else.
Yes, non-empty are very, very rare . Either the std::vector or the
llvm::SmallVector is fine here.
- Doug
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