Re: [cdt-dev] empty AST macro expansions

["Schorn, Markus" <Markus.Schorn@xxxxxxxxxxxxx>]

Hi Andrew,
I think you are right, IASTNode.getNodeLocations() should return the macro expansion, even if it expands to the empty token. Please file a bug containing a code-snippet that illustrates the problem. I will look into the issue.
Markus.

-----Original Message-----
From: cdt-dev-bounces@xxxxxxxxxxx [mailto:cdt-dev-bounces@xxxxxxxxxxx] On Behalf Of Andrew Eidsness
Sent: Tue, 29. 01. 2013 13:02
To: CDT General developers list.
Subject: Re: [cdt-dev] empty AST macro expansions

I actually want to know if a particular node was created as the result of a particular macro's expansion.  I.e., Instead of getting all expansions of the target macro (as shown in this code sample), I would like to find out if my IASTNode, referenced my target macro.

Oh, perhaps you mean that I can get all the references, and then use #getImageLocation on each to see if it is contained within the #getImageLocation of the IASTName of my target node?

-Andrew

On 13-01-29 01:43 AM, Schorn, Markus wrote:
> If you are looking for references of a macro you can simply use :
>
> IASTPreprocessorMacroDefinition macroDef= ...
> IBinding macro = macroDef.getName().resolveBinding();
> IASTName[] references= IASTTranslationUnit.getReferences(macro);
>
> Markus.
>
> -----Original Message-----
> From: cdt-dev-bounces@xxxxxxxxxxx [mailto:cdt-dev-bounces@xxxxxxxxxxx] 
> On Behalf Of Andrew Eidsness
> Sent: Mon, 28. 01. 2013 22:52
> To: cdt-dev@xxxxxxxxxxx
> Subject: [cdt-dev] empty AST macro expansions
>
> I'm trying to use the AST to discover whether a specific macro was used to create a particular node in the AST.  I'm calling IASTNode.getNodeLocations and looking for instances of IASTMacroExpansionLocation that reference the target macro.
>
> This works if the macro expands to a real value, but does not work when the expansion is to nothing.  E.g., expansions of the first macro are found, expansions of the second are not:
>
> 	#define FOUND     found
> 	#define NOT_FOUND
>
> The reason for the difference is the implementation of LocationCtxContainer.collectLocations.
>
> In both cases, the LocationCtxMacroExpansion is present in the fChildren list.  However, in the NOT_FOUND case, the child's fSequenceNumber is the same as childEndSequenceNumber (since length is 0).
>
> Approximately:
>
> 	if (sequenceNumber<  child.fSequenceNumber) {
> 	// ...
> [159]		sequenceNumber= child.fSequenceNumber;
> 	}
>
> 	// ...
> [164]	if (sequenceNumber<  childEndSequenceNumber) {
> 		child.collectLocations( // ...
>
> The loop's counter, sequenceNumber, is advanced (on line 159), which is before the check to see if the child is within the target range (on line 164).
>
> The questions that I have are:
>
> 	1) Is there a better way to do what I want?  The expansion that I'm looking for is stored in the node's fChildren list, maybe there is a different way to access it?
>
> 	2) Is this a bug or a feature?  :-)  Is there other code that depends on empty expansions being removed from the result?
>
> If it is a bug, then I could submit a patch to fix it.  My first ideas are:
> 	a) empty expansions should be given a sequenceLength of 1 when the 
> LocationCtxMacroExpansion is created, or
>
> 	b) the sequenceNumber counter should not be incremented until the child is fully processed.
>
> -Andrew
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