Re: [PATCH] dissect: add support for _Generic

[Oleg Nesterov <oleg@xxxxxxxxxx>]

On 07/29, Luc Van Oostenryck wrote:
>
> OTOH, I wonder what can be done without first evaluating
> (the type of) the controlling expression and the types of the map
> (if I understand correctly, evaluation is avoided in dissect).

Yes. I'll try to think a bit more, but so far I think I'll simply
send the patch below.

Test-case:

	void func(void)
	{
		_Generic(a,
			int:		b,
			void:		c,
			default:	d,
		) = e;
	}

output:

   1:6                    def   f func                             void ( ... )
   3:18  func             ---   v a                                bad type
   4:33  func             -w-   v b                                bad type
   5:33  func             -w-   v c                                bad type
   6:33  func             -w-   v d                                bad type
   7:13  func             -r-   v e                                bad type


Of course, technically this is wrong, it looks as if all 3 variables are
modified. But not that bad imo, dissect doesn't even try to be "precise",
and this output still looks useful for the indexing/etc.

Oleg.


--- a/dissect.c
+++ b/dissect.c
@@ -342,7 +342,6 @@ again:
 	case EXPR_TYPE:		// [struct T]; Why ???
 	case EXPR_VALUE:
 	case EXPR_FVALUE:
-	case EXPR_GENERIC:
 
 	break; case EXPR_LABEL:
 		ret = &label_ctype;
@@ -472,6 +471,17 @@ again:
 		} while ((expr = expr->down));
 	}
 
+	break; case EXPR_GENERIC: {
+		struct type_expression *map;
+
+		do_expression(U_VOID, expr->control);
+
+		for (map = expr->map; map; map = map->next)
+			ret = do_expression(mode, map->expr);
+		if (expr->def)
+			ret = do_expression(mode, expr->def);
+	}
+
 	break; case EXPR_SYMBOL:
 		ret = report_symbol(mode, expr);
 	}