[cfe-commits] [Patch] PR14922 - Improve Attr::printPretty

[Richard Smith]

On Mon, Jan 14, 2013 at 11:40 AM, Michael Han <fragmentshaders at gmail.com>wrote:

> Hi Richard,
>
> I think that is a great idea but I am not sure what value to pass to Attr
> when it's constructed in SemaDeclAttr.cpp. I was hoping to reuse the syntax
> enumerator value as the spelling list index but it does not work for all
> cases (e.g. alignment attribute in GNU syntax has two spellings.).
>
> Alternatively, at the time we construct an Attr, there is enough
> information (both the syntax and the actual spelling) we can use to print
> the attribute in full fidelity. We can pass the spelling string to the
> Attr, besides the syntax used as this patch did, so the printer will know
> which syntax and spelling to select. It would be more elegant to encode
> both information as a single index into the spelling list but I haven't
> figured out how to do that. Any suggestions on this?
>

You would need to teach TableGen to emit a function which maps the
attribute syntax, scope, and name to a spelling index (and to use the
spelling index when printing the attribute). You can then use that to add a
method to AttributeList to get the spelling index for an attribute.


> Cheers
> Michael
>
>
> On Fri, Jan 11, 2013 at 5:14 PM, Richard Smith <richard at metafoo.co.uk>wrote:
>
>> Hi,
>>
>> On Fri, Jan 11, 2013 at 3:53 PM, Michael Han <fragmentshaders at gmail.com>wrote:
>>
>>> Hi,
>>>
>>> Attached patch is to fix PR14922. Currently when print an attribute the
>>> GNU syntax will always be used, even if the attribute has no GNU syntax.The
>>> fix is to pass the syntax flag when constructing the Attr node and take
>>> that into consideration when printing the attribute. The name of actual
>>> attribute gets printed is read from table gen definition file so there is
>>> still some limitations, for example, when an attribute has multiple
>>> spellings, the first spelling is used; and the namespace of the attribute
>>> (in case it's a C++11 attribute) is not printed. I test the patch locally
>>> in my project which has access to Clang AST but I am not sure how to write
>>> a stand alone test to test the attribute pretty print.  After this patch
>>> gets in I'll send another patch which updates the SemaDeclAttr to pass the
>>> actual syntax flag from AttributeList to Attr.
>>
>>
>> I don't think this is the best approach: it still always uses the first
>> spelling, so it still won't produce the right string for
>> __attribute__((aligned(...))) versus __declspec(alignment(...)) versus
>> [[gnu::aligned(...)]] versus alignas(...).
>>
>> Since we already have a list of possible spellings for an attribute in
>> the attribute definition (which incorporates the syntax used), how about
>> just storing an index into that list on the Attr?
>>
>
>
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