I'm still wrapping my head around this, but we're doing some heavy macro programming in swift/Parse/Tokens.def. We define macros such as KEYWORD and then include the file, which allows different things to happen based on what macros we've defined beforehand.
Because it's using macros, subsequent includes of Tokens.def will have those same old macros defined unless they are subsequently undefined. That is actually happening in the bottom of the Tokens.def now, but apparently that wasn't always the case and there is some leftover code floating around that tries to deal with it. Sometimes (see SyntaxModel.cpp lines 98-100) we then #undef the macro afterward, in effect manually cleaning up after ourselves. In Lexer.cpp line 546 we define KEYWORD just to redefine it to be empty on line 602 presumably to avoid the previous definition stepping on our toes in the next couple of lines. Of course, the include already cleaned that up. I think we should go through and try to be more consistent with this. Tokens.def should have a comment block explaining exactly which macros will be checked and just specifying they'll all be undefined afterward, and all include usages should get rid of empty defines and undefines. Does that make sense? _______________________________________________ swift-dev mailing list swift-dev@swift.org https://lists.swift.org/mailman/listinfo/swift-dev
