[cfe-dev] Lexing empty macros

[Emerson Murphy-Hill]

I'm having a bit of difficulty with the lexer.  It's been working  
dandy for me for the most part, but has some problems when lexing over  
macro expansions that are empty.

Defining this macro:

#ifndef MyMacro
#define MyMacro int g;
#endif

and lexing over this:

MyMacro int x;

is no problem.  But defining the macro thusly:

#ifndef MyMacro
#define MyMacro
#endif

or:

#ifndef MyMacro
#define MyMacro /*some comment*/
#endif

causes a EXC_BAD_ACCESS here:

#0	clang::TokenLexer::isAtEnd at TokenLexer.h:122
#1	clang::TokenLexer::Lex at TokenLexer.cpp:279
#2	clang::Preprocessor::Lex at Preprocessor.h:262
#3	clang::Preprocessor::HandleMacroExpandedIdentifier at  
PPMacroExpansion.cpp:205
#4	clang::Preprocessor::HandleIdentifier at Preprocessor.cpp:532
#5	clang::Lexer::LexIdentifier at Lexer.cpp:534
#6	clang::Lexer::LexTokenInternal at Lexer.cpp:1314
#7	clang::Lexer::Lex at Lexer.h:141

(Actually, in the comment case, I'm not entirely sure if the comment  
gets expanded or simply removed by the preprocessor before expansion.)

This problem seems odd because the source file is getting parsed by  
clang correctly the first time around (for instance, I can run the  
clang driver and emit HTML, no problem).  But when I make a new lexer  
(re-using the preprocessor from the original parsing), I get the above  
errors.  Is there some lexer or preprocessor setting that I'm missing?

Thanks,

Emerson


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