[cfe-dev] Distinguish between array parameters and pointer parameters in the AST.

[steve naroff]

On Feb 20, 2009, at 12:22 PM, Roberto Bagnara wrote:

> steve naroff wrote:
>> On Feb 20, 2009, at 11:26 AM, Paolo Bolzoni wrote:
>>> dear cfe list,
>>>
>>> According to the clang AST the two parameters' type of this function
>>> declaration are the same:
>>>
>>> int f(int a[], int* b);
>>>
>>> while it makes sense, I'd like to distinguish.
>>> Is it not possible?
>>>
>> Not currently. Here is a comment from  
>> Sema::Sema::ActOnParamDeclarator():
>>  // Perform the default function/array conversion (C99  
>> 6.7.5.3p[7,8]).
>>  // Doing the promotion here has a win and a loss. The win is the  
>> type for
>>  // both Decl's and DeclRefExpr's will match (a convenient  
>> invariant for the
>>  // code generator). The loss is the orginal type isn't preserved.  
>> For example:
>>  //
>>  // void func(int parmvardecl[5]) { // convert "int [5]" to "int *"
>>  //    int blockvardecl[5];
>>  //    sizeof(parmvardecl);  // size == 4
>>  //    sizeof(blockvardecl); // size == 20
>>  // }
>>  //
>>  // For expressions, all implicit conversions are captured using the
>>  // ImplicitCastExpr AST node (we have no such mechanism for Decl's).
>>  //
>>  // FIXME: If a source translation tool needs to see the original  
>> type, then
>>  // we need to consider storing both types (in ParmVarDecl)...
>>  // HTH,
>
> Thanks Steve.  In our case we need to see the original type: there are
> coding rules that we need to check where the distincion is crucial.
> For instance:
>
> int f(int a[], int* b) {
>   a[0] = 0;     /* Compliant. */
>   b[5] = 0;     /* Not Compliant: as b was not declared as an array,
>                                   MISRA rule 17.4 is violated.  */
> }
>
> How difficult would be to address the FIXME above?

Actually, I think it's already been done:-)

See OriginalParmVarDecl, which is a subclass of ParmVarDecl.

Does this solve your problem?

snaroff



>
> Best,
>
>   Roberto
>
> -- 
> Prof. Roberto Bagnara
> Computer Science Group
> Department of Mathematics, University of Parma, Italy
> http://www.cs.unipr.it/~bagnara/
> mailto:bagnara at cs.unipr.it

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