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Diffstat (limited to 'clang/docs')
| -rw-r--r-- | clang/docs/LanguageExtensions.rst | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/clang/docs/LanguageExtensions.rst b/clang/docs/LanguageExtensions.rst index 1917e2b73c2..e8826b5b360 100644 --- a/clang/docs/LanguageExtensions.rst +++ b/clang/docs/LanguageExtensions.rst @@ -1255,6 +1255,23 @@ Further examples of these attributes are available in the static analyzer's `lis Query for these features with ``__has_attribute(ns_consumed)``, ``__has_attribute(ns_returns_retained)``, etc. +objc_msg_lookup_stret +--------------------- + +Traditionally, if a runtime is used that follows the GNU Objective-C ABI, a +call to objc_msg_lookup() would be emitted for each message send, which would +return a pointer to the actual implementation of the method. However, +objc_msg_lookup() has no information at all about the method signature of the +actual method. Therefore, certain features like forwarding messages cannot be +correctly implemented for methods returning structs using objc_msg_lookup(), as +methods returning structs use a slightly different calling convention. + +To work around this, Clang emits calls to objc_msg_lookup_stret() instead for +methods that return structs if the runtime supports this, allowing the runtime +to use a different forwarding handler for methods returning structs. + +To check if Clang emits calls to objc_msg_lookup_stret(), +__has_feature(objc_msg_lookup_stret) can be used. Function Overloading in C ========================= |
