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Partially process a file using a preprocessor

We inherited a very minimized project (500kloc) with the conditional logic of the lot of conditional logic of the preprocessor, most of which is no longer relevant, and I want to clear it.

Can I use the preprocessor¹ to extend only some conditional logic and leave all other macros of the preprocessor, define and enable only at the output?

¹ Here, by "preprocessor", I really mean "any tool", or the standard C preprocessor, then I can install it, or even a hacked Perl or Python script.

For example, suppose we have this code set:

#include <foo>
#define baz
#define bar(a) do{(a)+1} \
               while(0)
#ifdef X
  #if Y > 20
    #if Z > 5
      so_far_so_good = true;
    #endif
    #ifdef baz
    something();
    #endif
  #else
    otherthing();
  #endif
#else
  #if Z > 10
    wow().this.is.bad;
  #endif
#endif

, (, , , ), CPP, , , . . :

cpptreadlight -DY=22 --only=Y

:

#include <foo>
#define baz
#define bar(a) do{(a)+1} \
               while(0)
#ifdef X
    #if Z > 5
      so_far_so_good = true;
    #endif
    #ifdef baz
    something();
    #endif
#else
  #if Z > 10
    wow().this.is.bad;
  #endif
#endif


cpptreadlight -DY=22 -DZ=8 -DX --only=Y,baz,Z

:

#include <foo>
#define bar(a) do{(a)+1} \
               while(0)
#ifdef X
      so_far_so_good = true;
    something();
#else
#endif

, X , , --only. , baz --only , .

: , ( gsub , , ):

function escape_tr() { 
   gsub "#(define|include)" '@@@\1' < $1 | 
     (echo '#include "simple.h"' && gsub '\\$' "%%%") | 
       cpp -C -P -DY=301 -DZ > $1.new 
}

, , , simple.h. , #line .

, , #define . , , , . . .

#if, #else #endif , regex. , cpp, .

, , , , - . , , .

+5
2

unifdef", , .

+8

boost.wave

boost.wave:

, Wave :

  • ++ (ISO/IEC 14882: 1998) 1 C99 (INCITS/ISO/IEC 9899: 1999).
  • [4] (: -)
  • STL / Boost ( )
  • ++.
0

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