清除c/c++代码中条件编译部分的程序，帮助阅读源代码，生成好的tags

#include <stdio.h> #include <stdlib.h> #include <ctype.h> #include <list> #include <set> #include <stack> #include <string> #include <iostream> using namespace std; /* * size of the buffer for a line limits to 8KB * if a line is longger than 8KB, it will be interrupted. */ #define BUFSIZE 1024*8 /* * let set the macro bigger than 255 to avoid ascii chars. * and, make it can adapt bit or/and operate. */ #define DEFINE 256 #define ELIF 512 #define ELSE 1024 #define ENDIF 2048 #define IF 4096 #define IFDEF 8192 #define IFNDEF 16384 #define NORMAL 32768 #define UNDEF 65536 #define OTHERS 131072 #define EQUAL 300 #define NEQUAL 301 #define ENDS 302 #define PASS_SPACE2(buf,i) while( ++i<buf.length() && isspace( buf[i]) ); /* * yytext is the value for some token. * there are two global variables. */ string yytext; /* save the result of lex analyze. */ int lineno = 1; /* current line number. */ int comment_flag = 0; /* whether to delete or comment the undefined parts. */ /* * function eatword * push every char which construct the word into yytext. * this function only push strings into yytext, never clear it. */ int eatword(string& buf, unsigned int& i){ /* first pass spaces. */ if ( isspace(buf[i]) ) { PASS_SPACE2(buf,i); } /* check if it is a word or a char. */ /* if it's word */ if ( isalpha(buf[i]) || buf[i] == '_' ) { yytext.push_back( buf[i] ); i++; while ( i<buf.length() && ( isalnum(buf[i]) || buf[i] == '_' ) ) { yytext.push_back( buf[i] ); i++; } /* check if keyword. */ if ( yytext.compare("if") == 0 ) { return IF; }else if( yytext.compare( "define" ) == 0 ){ return DEFINE; }else if( yytext.compare( "elif" ) == 0 ){ return ELIF; }else if( yytext.compare( "else" ) == 0 ){ return ELSE; }else if( yytext.compare( "endif" ) == 0 ){ return ENDIF; }else if( yytext.compare( "ifdef" ) == 0 ){ return IFDEF; }else if( yytext.compare( "ifndef" ) == 0 ){ return IFNDEF; }else if( yytext.compare( "undef" ) == 0 ){ return UNDEF; }else { return OTHERS; } }else if( buf[i] == '=' || buf[i] == '!' ){ yytext.push_back( buf[i] ); if ( buf[++i] == '=' ) { yytext.push_back( '=' ); i++; return (buf[i-2] == '=') ? EQUAL : NEQUAL; }else { return buf[i-1]; } }else if( i == buf.length() ){ return ENDS; }else { /* it's a char */ yytext.push_back( buf[i] ); /* * important: this function has the responsibility to modify the i to next position * because i is the reference type. * we make the contract that we only modified i in this function. */ i++; return buf[i-1]; } } /* * analyze a whole line. * important: * yytext is cleared here, and in function lex,it only push chars into it. * * this function returns an int or a char. */ int parse_line( string& buf, set<string>& env ){ yytext.clear(); /* var i can modified only by function lex !!!!!!! */ unsigned int i = 0; int first_word = eatword( buf, i ); /* check if it start with # */ if ( first_word != '#' ) { return NORMAL; }else { yytext.clear(); /* i++; */ first_word = eatword( buf, i ); } switch( first_word ){ case DEFINE: yytext.clear(); /* get next word into yytext. */ eatword( buf, i ); /* * this section reserved for next develop of macro launching. */ #if 0 /* look forward for a char */ if ( buf[i] == '(' ) { stack<int> s; s.push( 1 ); yytext.push_back( '(' ); i++; while ( !s.empty( ) ) { int tmp = eatword( buf, i ); if ( tmp == ')' ) { s.pop( ); }else if( tmp == '(' ){ s.push(1); } } } #endif return DEFINE; case ELIF: case IF: yytext.clear(); eatword( buf, i ); if ( yytext.compare( "defined" ) == 0 ) { yytext.clear(); eatword( buf, i ); return first_word == IF ? IFDEF : ELIF|IFDEF; }else if( yytext[0] == '!' ){ eatword( buf, i ); if ( yytext.compare( "!defined" ) == 0 ){ yytext.clear(); eatword( buf, i ); return first_word == IF ? IFNDEF : ELIF|IFNDEF; }else { return first_word; } }else { int x1 = (env.find( yytext )!=env.end()) ? 1 : 0; yytext.clear(); int oper = eatword( buf, i ); if ( oper != EQUAL && oper != NEQUAL && oper != ENDS ) { printf( "error: lack of != or == at line %d\n",lineno ); cout<<buf<<endl; exit(1); }else if( oper == ENDS ){ (x1 != 0)? yytext.push_back('1') : yytext.push_back('0'); return first_word; } yytext.clear(); eatword( buf, i ); int x2 = (env.find( yytext ) != env.end()) ? 1 : 0; int comp_res = (oper == EQUAL) ? (x1 == x2) : (x1 != x2); yytext.clear(); (comp_res != 0) ? yytext.push_back('1') : yytext.push_back('0'); return first_word; } case IFDEF: case IFNDEF: yytext.clear(); eatword( buf, i ); return first_word; case UNDEF: yytext.clear(); eatword( buf, i ); return UNDEF; default: return first_word; /* other preprocess command. */ } } void killpp4( list<string>& l, set<string>& env ){ /* * top of status stack is the latest saved elif_flag. */ stack<int> status; list<string>::iterator iter; /* * this var is used for if...elif...elif...end. * because in these sections only one section could be execute, * if one section in if...elif...elif...end structure has * ever executed, let's mark it. * init it to 0 */ int ever_true = 0; /* * this var is used for determine the current status is defined or * not defined, the former the line reserved, and the latter the line ignored. */ int elif_flag = 1; lineno = 1; for( iter = l.begin(); iter != l.end(); ++lineno ){ int result = parse_line( *iter, env ); switch( result ){ case IF: status.push( elif_flag ); if( yytext[0] == '0' ) elif_flag = 0; else elif_flag = 1; if( elif_flag != 0 ) ever_true = 1; elif_flag &= status.top(); break; case IFDEF: status.push( elif_flag ); elif_flag = env.find( yytext ) != env.end(); if( elif_flag != 0 ) ever_true = 1; elif_flag &= status.top(); break; case IFNDEF: status.push( elif_flag ); elif_flag = env.find( yytext ) == env.end(); if( elif_flag != 0 ) ever_true = 1; elif_flag &= status.top(); break; case ENDIF: if( !status.empty() ){ elif_flag = status.top(); status.pop(); /* when a select structure ends, reset ever_true to 0 */ ever_true = 0; }else { printf("syntax error at line %d\n",lineno); cout<<*iter<<endl; exit(1); } break; case ELSE: elif_flag = !elif_flag; elif_flag &= !ever_true; if( status.top() == 0 ) elif_flag = 0; break; case ELIF: if( elif_flag != 0 ) elif_flag = 0; else if ( yytext[0] != '0' ) { elif_flag = 1; } elif_flag &= !ever_true; if( elif_flag != 0 ) ever_true = 1; if( status.top() == 0 ) elif_flag = 0; break; case ELIF|IFDEF: if ( elif_flag != 0 ) { elif_flag = 0; }else if( env.find( yytext ) != env.end() ){ elif_flag = 1; } elif_flag &= !ever_true; if( elif_flag != 0 ) ever_true = 1; if( status.top() == 0 ) elif_flag = 0; break; case ELIF|IFNDEF: if ( elif_flag != 0 ) { elif_flag = 0; }else if( env.find( yytext ) == env.end() ){ elif_flag = 1; } elif_flag &= !ever_true; if( elif_flag != 0 ) ever_true = 1; if( status.top() == 0 ) elif_flag = 0; break; } if ( elif_flag ) { switch( result ){ case DEFINE: env.insert( yytext ); break; case UNDEF: if ( env.find( yytext ) != env.end() ) { env.erase( yytext ); } break; } }else { if ( comment_flag ) { (*iter).insert(0,"/* "); (*iter).append(" */"); iter++; }else { l.erase( iter++ ); } continue; } /*