(clang) How to parse macros themselves, getting an ast where possible? -

hi i'm using clang extract information c files. , i'm trying extract values of macros.

e.g. i'd want value '13' or ast (+ (* 3 4) 1):

#define some_constant 3*4+1 

or macro function, i'd want ast e.g. (some_macrofunc (x y) (+ (add4 x) (* y 9))) :

int add4(int q) {return q+4;} #define some_macrofunc(x,y) add4(x)+y*9 

so far i've managed iterate through macros via 'preprocessor' class's macro_begin() , macro_end() functions.

then i've gotten macro names, , 'macroinfo' class i've been able whether macro functionlike (including param names) or not. i've got access tokens in macro, able token kind e.g: string_literal, identifier, comma, l_paren, r_paren, etc.

so 2 things:

1. how access actual value of tokens, rather kinds.

2. is there way generate ast macros given tokens? 1 way thought parse source code, extract macros, , using names, add code including macros source , reparse ast.

e.g. like:

char *tempsome_constant = some_constant;     void tempsome_macrofunc(char *x, char *y) {some_macrofunc(x,y);} 

though method seems hacky, , have trouble macros aren't statement or expression like.

thanks.

edit: clarify want expanded body (until no macros left, non macro tokens) of each macro.

edit2 solved what:

if anyones interested intend expand body of macro manually.

"preprocessor.getspelling(token)" token value.

"preprocessor.getidentifiertable().get(stringref(spelling))" identinfo token.

and using "clang\lib\lex\ppmacroexpansion.cpp" reference.

still thinking how pass parser without reparsing whole source tree, shouldn't difficult figure out.

thanks ira baxter discussion, helped me iron out problem.

i working on similar. use clang front end collecting context (w.r.t. class, function etc.) in macro defined , use (pseudo) expression parser figure out if macro-body valid expression or not. ultimate goal transform macro c++ declaration. got paper accepted icsm-2012 explains how achieve this.

the tools -the demacrofier- used rid of macros hosted here

ira baxter's examples insightful in way macros used. however, %age of macros less \ref(an empirical analysis of c preprocessor use ernst et al.). currently, focusing more on common cases.