What does a C++ identifier ending in $_## mean?

Question

In trying to understand a .so from an Android game made with Cocos2d-x, I've come across identifiers like the following (after demangling):

SceneActionMap::updateTalkMode(float)::$_37 SceneActionMap::onTouchEndedTalk(cocos2d::Touch*, cocos2d::Event*)::$_38

I'm still a little shaky on ELF & the C++ ABI, but these names are found in .rodata and are referred to by some kind of structure in .data.rel.ro that seems RTTI related.

What kind of entities are $_37 and $_38? Are these anonymous functions generated by the NDK, or are they some kind of metadata about other functions?

Answer 1

its a lambda function, as example stack trace in google https://github.com/Microsoft/vscode-cpptools/issues/2117