Path Xcode 5空项目在标头搜索路径设置中具有未知路径

路径是

/Applications/Xcode.app/Contents/Developer/toolschains/xcodefault.xctoolschain/usr/include

那里有一个FlexLexer.h。不知道为什么需要此路径或此头文件。以下是FlexLexer.h的源代码：

// -*-C++-*-
// FlexLexer.h -- define interfaces for lexical analyzer classes generated
// by flex

// Copyright (c) 1993 The Regents of the University of California.
// All rights reserved.
//
// This code is derived from software contributed to Berkeley by
// Kent Williams and Tom Epperly.
//
//  Redistribution and use in source and binary forms, with or without
//  modification, are permitted provided that the following conditions
//  are met:

//  1. Redistributions of source code must retain the above copyright
//  notice, this list of conditions and the following disclaimer.
//  2. Redistributions in binary form must reproduce the above copyright
//  notice, this list of conditions and the following disclaimer in the
//  documentation and/or other materials provided with the distribution.

//  Neither the name of the University nor the names of its contributors
//  may be used to endorse or promote products derived from this software
//  without specific prior written permission.

//  THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
//  IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
//  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
//  PURPOSE.

// This file defines FlexLexer, an abstract class which specifies the
// external interface provided to flex C++ lexer objects, and yyFlexLexer,
// which defines a particular lexer class.
//
// If you want to create multiple lexer classes, you use the -P flag
// to rename each yyFlexLexer to some other xxFlexLexer.  You then
// include <FlexLexer.h> in your other sources once per lexer class:
//
//  #undef yyFlexLexer
//  #define yyFlexLexer xxFlexLexer
//  #include <FlexLexer.h>
//
//  #undef yyFlexLexer
//  #define yyFlexLexer zzFlexLexer
//  #include <FlexLexer.h>
//  ...

#ifndef __FLEX_LEXER_H
// Never included before - need to define base class.
#define __FLEX_LEXER_H

#include <iostream>
#  ifndef FLEX_STD
#    define FLEX_STD std::
#  endif

extern "C++" {

struct yy_buffer_state;
typedef int yy_state_type;

class FlexLexer {
public:
    virtual ~FlexLexer()    { }

    const char* YYText() const  { return yytext; }
    size_t YYLeng() const   { return yyleng; }

    virtual void
        yy_switch_to_buffer( struct yy_buffer_state* new_buffer ) = 0;
    virtual struct yy_buffer_state*
        yy_create_buffer( FLEX_STD istream* s, int size ) = 0;
    virtual void yy_delete_buffer( struct yy_buffer_state* b ) = 0;
    virtual void yyrestart( FLEX_STD istream* s ) = 0;

    virtual int yylex() = 0;

    // Call yylex with new input/output sources.
    int yylex( FLEX_STD istream* new_in, FLEX_STD ostream* new_out = 0 )
        {
        switch_streams( new_in, new_out );
        return yylex();
        }

    // Switch to new input/output streams.  A nil stream pointer
    // indicates "keep the current one".
    virtual void switch_streams( FLEX_STD istream* new_in = 0,
                    FLEX_STD ostream* new_out = 0 ) = 0;

    int lineno() const      { return yylineno; }

    int debug() const       { return yy_flex_debug; }
    void set_debug( int flag )  { yy_flex_debug = flag; }

protected:
    char* yytext;
    size_t yyleng;
    int yylineno;       // only maintained if you use %option yylineno
    int yy_flex_debug;  // only has effect with -d or "%option debug"
};

}
#endif // FLEXLEXER_H

#if defined(yyFlexLexer) || ! defined(yyFlexLexerOnce)
// Either this is the first time through (yyFlexLexerOnce not defined),
// or this is a repeated include to define a different flavor of
// yyFlexLexer, as discussed in the flex manual.
#define yyFlexLexerOnce

extern "C++" {

class yyFlexLexer : public FlexLexer {
public:
    // arg_yyin and arg_yyout default to the cin and cout, but we
    // only make that assignment when initializing in yylex().
    yyFlexLexer( FLEX_STD istream* arg_yyin = 0, FLEX_STD ostream* arg_yyout = 0 );

    virtual ~yyFlexLexer();

    void yy_switch_to_buffer( struct yy_buffer_state* new_buffer );
    struct yy_buffer_state* yy_create_buffer( FLEX_STD istream* s, int size );
    void yy_delete_buffer( struct yy_buffer_state* b );
    void yyrestart( FLEX_STD istream* s );

    void yypush_buffer_state( struct yy_buffer_state* new_buffer );
    void yypop_buffer_state();

    virtual int yylex();
    virtual void switch_streams( FLEX_STD istream* new_in, FLEX_STD ostream* new_out = 0 );
    virtual int yywrap();

protected:
    virtual size_t LexerInput( char* buf, size_t max_size );
    virtual void LexerOutput( const char* buf, size_t size );
    virtual void LexerError( const char* msg );

    void yyunput( int c, char* buf_ptr );
    int yyinput();

    void yy_load_buffer_state();
    void yy_init_buffer( struct yy_buffer_state* b, FLEX_STD istream* s );
    void yy_flush_buffer( struct yy_buffer_state* b );

    int yy_start_stack_ptr;
    int yy_start_stack_depth;
    int* yy_start_stack;

    void yy_push_state( int new_state );
    void yy_pop_state();
    int yy_top_state();

    yy_state_type yy_get_previous_state();
    yy_state_type yy_try_NUL_trans( yy_state_type current_state );
    int yy_get_next_buffer();

    FLEX_STD istream* yyin; // input source for default LexerInput
    FLEX_STD ostream* yyout;    // output sink for default LexerOutput

    // yy_hold_char holds the character lost when yytext is formed.
    char yy_hold_char;

    // Number of characters read into yy_ch_buf.
    size_t yy_n_chars;

    // Points to current character in buffer.
    char* yy_c_buf_p;

    int yy_init;        // whether we need to initialize
    int yy_start;       // start state number

    // Flag which is used to allow yywrap()'s to do buffer switches
    // instead of setting up a fresh yyin.  A bit of a hack ...
    int yy_did_buffer_switch_on_eof;


    size_t yy_buffer_stack_top; /**< index of top of stack. */
    size_t yy_buffer_stack_max; /**< capacity of stack. */
    struct yy_buffer_state ** yy_buffer_stack; /**< Stack as an array. */
    void yyensure_buffer_stack(void);

    // The following are not always needed, but may be depending
    // on use of certain flex features (like REJECT or yymore()).

    yy_state_type yy_last_accepting_state;
    char* yy_last_accepting_cpos;

    yy_state_type* yy_state_buf;
    yy_state_type* yy_state_ptr;

    char* yy_full_match;
    int* yy_full_state;
    int yy_full_lp;

    int yy_lp;
    int yy_looking_for_trail_begin;

    int yy_more_flag;
    int yy_more_len;
    int yy_more_offset;
    int yy_prev_more_offset;
};

}

#endif // yyFlexLexer || ! yyFlexLexerOnce