Merge branch 'variadic-enumerators'

This adds several changes to enumerator_t and linked_list_t to improve
portability.  In particular to Apple's ARM64 iOS platform, whose calling
convention for variadic and regular functions are different.  This means
that assigning a non-variadic function to a variadic function pointer,
as we did with our enumerator_t::enumerate() implementations and several
callbacks, will result in crashes as the called function will access the
arguments differently than the caller provided them.

To avoid this issue the enumerator_t interface is now fully variadic.
A new mandatory method is added, venumerate(), that takes a va_list with
the arguments provided while enumerating.  enumerate() is replaced with
a generic implementation that prepares a va_list and calls the
enumerator's venumerate() implementation.  As this allows passing the
arguments of one enumerator to another it avoids the five pointer hack
used by enumerator_create_nested() and enumerator_create_cleaner().
To simplify the implementation of venumerate() a helper macro is provided
that assigns values from a given va_list to local variables.

The signature of the callback passed to enumerator_create_filter() has
also changed significantly.  It's now required to enumerate over the
original enumerator in the callback as this avoids the previous in/out
pointer hack. The arguments to the outer enumerator are provided in a
va_list.

Similar changes to avoid such five pointer hacks affect the signatures
of the callbacks for linked_list_t's invoke_function() and find_first()
methods.  For the latter the return type also changed from status_t to
bool, which is important as SUCCESS is defined as 0, so checks for ==
SUCCESS will now fail.

1 files changed, 8 insertions, 4 deletions

diff --git a/src/libcharon/plugins/android_dns/android_dns_handler.c b/src/libcharon/plugins/android_dns/android_dns_handler.c
index 160a145d3..68bbaecb2 100644
--- a/src/libcharon/plugins/android_dns/android_dns_handler.c
+++ b/src/libcharon/plugins/android_dns/android_dns_handler.c
@@ -182,12 +182,15 @@ METHOD(attribute_handler_t, release, void,
 }
 
 METHOD(enumerator_t, enumerate_dns, bool,
-	enumerator_t *this, configuration_attribute_type_t *type, chunk_t *data)
+	enumerator_t *this, va_list args)
 {
+	configuration_attribute_type_t *type;
+	chunk_t *data;
+
+	VA_ARGS_VGET(args, type, data);
 	*type = INTERNAL_IP4_DNS;
 	*data = chunk_empty;
-	/* stop enumeration */
-	this->enumerate = (void*)return_false;
+	this->venumerate = return_false;
 	return TRUE;
 }
 
@@ -198,7 +201,8 @@ METHOD(attribute_handler_t, create_attribute_enumerator, enumerator_t *,
 	enumerator_t *enumerator;
 
 	INIT(enumerator,
-		.enumerate = (void*)_enumerate_dns,
+		.enumerate = enumerator_enumerate_default,
+		.venumerate = _enumerate_dns,
 		.destroy = (void*)free,
 	);
 	return enumerator;