[cfe-dev] Get the number of bits of a bit field with libclang?

[Argyrios Kyrtzidis]

On May 22, 2012, at 12:35 PM, Jordy Rose wrote:

> 
> On May 22, 2012, at 15:28, Argyrios Kyrtzidis wrote:
> 
>> On May 22, 2012, at 11:42 AM, Jacob Carlborg wrote:
>> 
>>> Is it possible to get the number of bits of a bit field with libclang?
>>> 
>>> struct Foo
>>> {
>>>   int a : 1;
>>> };
>>> 
>>> I noticed I could traverse to the "value" of "a" and the type of the 
>>> cursor was CXCursor_IntegerLiteral. But is it possible to get the actual 
>>> value?
>> 
>> No, are you interested in submitting a patch ? I suggest something like "clang_Cursor_getBitWidthValue(CXCursor)" similar to how clang_Cursor_getNumArguments(CXCursor C) works, with the difference that it can return "unsigned" and 0 if the cursor is not a bitfield.
> 
> Unfortunately, C99 6.7.2.1p3 states that unnamed bit fields may have 0 width, and 6.7.2.1p11 explains that it's a way to separate packed units.
> 
> int a : 1;
> int : 0;
> int b: 1;
> // a and b will be in different bytes, possibly different words.
> 
> You'll need another sentinel value, a dual return, or maybe just an assert to make this work.

Good point, I suggest same behavior as clang_Cursor_getNumArguments (int with -1 for non bitfield).

> 
> Jordy