dwarf_loader: Don't stop processing after finding unsupported tag

After emitting a warning that a tag is not supported __die__process_tag
was returning NULL, making die__process_unit think that the problem
was insufficient memory.

Introduce a global variable 'unsupported_tag' and return it instead,
that way die__process_unit can distinguish ENOMEM from unsupported tags.

Reported-by: Thiago Macieira <[email protected]>
Tested-by: Thiago Macieira <[email protected]>
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

dwarf_loader.c

@@ -1539,6 +1539,8 @@ static struct tag *die__create_new_function(Dwarf_Die *die, struct cu *cu)
 	return function ? &function->proto.tag : NULL;
 }
 
+static struct tag unsupported_tag;
+
 static struct tag *__die__process_tag(Dwarf_Die *die, struct cu *cu,
 				      int top_level, const char *fn)
 {
@@ -1578,7 +1580,7 @@ static struct tag *__die__process_tag(Dwarf_Die *die, struct cu *cu,
 		tag = die__create_new_variable(die, cu);	break;
 	default:
 		__cu__tag_not_handled(die, fn);
-		tag = NULL;
+		tag = &unsupported_tag;
 		break;
 	}
 
@@ -1595,6 +1597,9 @@ static int die__process_unit(Dwarf_Die *die, struct cu *cu)
 		if (tag == NULL)
 			return -ENOMEM;
 
+		if (tag == &unsupported_tag)
+			continue;
+
 		long id = -1;
 		cu__add_tag(cu, tag, &id);
 		cu__hash(cu, tag);