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C指針原理教程之C指針基礎(chǔ)

更新時(shí)間：2019年02月07日 11:36:47 作者：myhaspl

指針是一個(gè)特殊的變量，它里面存儲的數(shù)值被解釋成為內(nèi)存里的一個(gè)地址。要搞清一個(gè)指針需要搞清指針的四方面的內(nèi)容：指針的類型、指針?biāo)赶虻念愋汀⒅羔樀闹祷蛘呓兄羔標(biāo)赶虻膬?nèi)存區(qū)、指針本身所占據(jù)的內(nèi)存區(qū)。

tcctok.h定義了C語言的詞法分析的基本元素，主要定義了關(guān)鍵字。

/ keywords /
     DEF(TOK_INT, "int")
     DEF(TOK_VOID, "void")
     DEF(TOK_CHAR, "char")
     DEF(TOK_IF, "if")
     DEF(TOK_ELSE, "else")
     DEF(TOK_WHILE, "while")
     DEF(TOK_BREAK, "break")
     DEF(TOK_RETURN, "return")
     DEF(TOK_FOR, "for")
     DEF(TOK_EXTERN, "extern")
     DEF(TOK_STATIC, "static")
     DEF(TOK_UNSIGNED, "unsigned")
     DEF(TOK_GOTO, "goto")
     DEF(TOK_DO, "do")
     DEF(TOK_CONTINUE, "continue")
     DEF(TOK_SWITCH, "switch")
     DEF(TOK_CASE, "case")

..............................

同時(shí)定義了條件編譯的相關(guān)內(nèi)容

/*****/
/ the following are not keywords. They are included to ease parsing /
/ preprocessor only /
     DEF(TOK_DEFINE, "define")
     DEF(TOK_INCLUDE, "include")
     DEF(TOK_INCLUDE_NEXT, "include_next")
     DEF(TOK_IFDEF, "ifdef")
     DEF(TOK_IFNDEF, "ifndef")
     DEF(TOK_ELIF, "elif")
     DEF(TOK_ENDIF, "endif")
     DEF(TOK_DEFINED, "defined")

在i386-tok.h中定義了匯編的相關(guān)關(guān)鍵詞

/ ------------------------------------------------------------------ /
/ WARNING: relative order of tokens is important. /

/ register /
DEF_ASM(al)
DEF_ASM(cl)
DEF_ASM(dl)
DEF_ASM(bl)
DEF_ASM(ah)
DEF_ASM(ch)
DEF_ASM(dh)
DEF_ASM(bh)
DEF_ASM(ax)
DEF_ASM(cx)
DEF_ASM(dx)
DEF_ASM(bx)
DEF_ASM(sp)
DEF_ASM(bp)
DEF_ASM(si)
DEF_ASM(di)
DEF_ASM(eax)
DEF_ASM(ecx)
DEF_ASM(edx)
DEF_ASM(ebx)
DEF_ASM(esp)
DEF_ASM(ebp)
DEF_ASM(esi)
DEF_ASM(edi)
#ifdef TCC_TARGET_X86_64
DEF_ASM(rax)
DEF_ASM(rcx)
DEF_ASM(rdx)

...........................

............................

在x86_64-asm.h中定義了64位匯編相關(guān)關(guān)鍵字

     DEF_ASM_OP0(clc, 0xf8) / must be first OP0 /
     DEF_ASM_OP0(cld, 0xfc)
     DEF_ASM_OP0(cli, 0xfa)
     DEF_ASM_OP0(clts, 0x0f06)
     DEF_ASM_OP0(cmc, 0xf5)
     DEF_ASM_OP0(lahf, 0x9f)
     DEF_ASM_OP0(sahf, 0x9e)
     DEF_ASM_OP0(pushfl, 0x9c)
     DEF_ASM_OP0(popfl, 0x9d)
     DEF_ASM_OP0(pushf, 0x9c)
     DEF_ASM_OP0(popf, 0x9d)
     DEF_ASM_OP0(stc, 0xf9)
     DEF_ASM_OP0(std, 0xfd)
     DEF_ASM_OP0(sti, 0xfb)
     DEF_ASM_OP0(aaa, 0x37)

先從幾個(gè)重要文件入手。

libtcc.c

/
  TCC - Tiny C Compiler
 
  Copyright (c) 2001-2004 Fabrice Bellard
 
 This library is free software; you can redistribute it and/or
 modify it under the terms of the GNU Lesser General Public
 License as published by the Free Software Foundation; either
 version 2 of the License, or (at your option) any later version.
 
 This library is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 Lesser General Public License for more details.
 
 You should have received a copy of the GNU Lesser General Public
 License along with this library; if not, write to the Free Software
 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */

#include "tcc.h"

/****/
/ global variables /
使用GCC擴(kuò)展還是TCC擴(kuò)展

/ use GNU C extensions /
ST_DATA int gnu_ext = 1;

/ use TinyCC extensions /
ST_DATA int tcc_ext = 1;

ST_DATA 結(jié)構(gòu)標(biāo)注TCC狀態(tài)。
/ XXX: get rid of this ASAP /
ST_DATA struct TCCState *tcc_state;

/****/

根據(jù)標(biāo)志包含一些相應(yīng)TCC文件。

#ifdef ONE_SOURCE
#include "tccpp.c"
#include "tccgen.c"
#include "tccelf.c"
#include "tccrun.c"
#ifdef TCC_TARGET_I386
#include "i386-gen.c"
#endif
#ifdef TCC_TARGET_ARM
#include "arm-gen.c"
#endif
#ifdef TCC_TARGET_C67
#include "c67-gen.c"
#endif
#ifdef TCC_TARGET_X86_64
#include "x86_64-gen.c"
#endif
#ifdef CONFIG_TCC_ASM
#include "tccasm.c"
#if defined TCC_TARGET_I386 || defined TCC_TARGET_X86_64
#include "i386-asm.c"
#endif
#endif
#ifdef TCC_TARGET_COFF
#include "tcccoff.c"
#endif
#ifdef TCC_TARGET_PE
#include "tccpe.c"
#endif
#endif / ONE_SOURCE /

CONFIG_TCC_ASM打開內(nèi)聯(lián)匯編的開關(guān)
/****/
#ifndef CONFIG_TCC_ASM
ST_FUNC void asm_instr(void)
{
tcc_error("inline asm() not supported");
}
ST_FUNC void asm_global_instr(void)
{
tcc_error("inline asm() not supported");
}
#endif

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