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輸入檔案:defc.c0

x = 3;
y=5;
if ((x+y)>6)
  z = 0;
else
  z = 1;

i=0;
while (i<100) {
    s = s + i;
    i++;
}

def sum(n) {
    for (i=0; i<n; i++)
        s = s + i;
    return s;
}

def swap(a, b) {
    t = a;
    a = b;
    b = t;
}

total=sum(10);

=swap(x, y);

編譯執行結果

D:\oc\compiler>gcc defc.c -o defc

D:\oc\compiler>defc defc.c0
==== compile file:defc.c0 ========
         =        t1       3
         =        x        t1
         =        t2       5
         =        y        t2
         +        t3       x        y
         =        t4       6
         >        t5       t3       t4
         ifnot    t5       _L0:
         =        t6       0
         =        z        t6
_L0:
         =        t7       1
         =        z        t7
         =        t8       0
         =        i        t8
_L1:
         =        t9       100
         <        t10      i        t9
         ifnot    t10      _L2:
         +        t11      s        i
         =        s        t11
         ++       i
         goto     _L1:
_L2:
_sum:    function
         PARAM    n
         =        t12      0
         =        i        t12
_L4:
         <        t13      i        n
         ifnot    t13      _L5:
         +        t14      s        i
         =        s        t14
         ++       i
         goto     _L4:
_L5:
         RET      s
_swap:   function
         PARAM    a
         PARAM    b
         =        t        a
         =        a        b
         =        b        t
         =        t15      10
         ARG      t15
         CALL     sum      t16
         =        total    t16
         ARG      x
         ARG      y
         CALL     swap     t17
======= symTable ========
sym[1]=x
sym[2]=3
sym[3]=y
sym[4]=5
sym[5]=6
sym[6]=_L0:
sym[7]=z
sym[8]=0
sym[9]=1
sym[10]=i
sym[11]=_L1:
sym[12]=_L2:
sym[13]=100
sym[14]=s
sym[15]=_L3:
sym[16]=_sum:
sym[17]=n
sym[18]=_L4:
sym[19]=_L5:
sym[20]=_L6:
sym[21]=_swap:
sym[22]=a
sym[23]=b
sym[24]=t
sym[25]=total
sym[26]=sum
sym[27]=10
sym[28]=swap
======= strTable ========
x.3.y.5.6._L0:.z.0.1.i._L1:._L2:.100.s._L3:._sum:.n._L4:._L5:._L6:._swap:.a.b.t.
total.sum.10.swap.

程式:defc.c

#include <stdio.h>
#include <assert.h>
#include <stdarg.h>

// ================== 基本常數 ===================
#define FALSE   0
#define TRUE    1
#define BOOL    unsigned char
#define NIL        -1

#define LEN 256

#define SYM_TABLE_MAX 1000
#define STR_TABLE_MAX 10000

#define SPACE " \t\n\r"         // 空白字元
#define ALPHA "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ" // 英文字母
#define DIGIT "0123456789"        // 數字字元
#define OP "+-*/%<=>!&|"        // 運算符號字元集 (用來取得 +,-,*,/, ++, ...)

char *keys[] = {"if", "else", "for", "while", "def", "return", "int", "char", "float", NULL};

#define STRING "STRING"
#define NUMBER "NUMBER"
#define FLOAT  "FLOAT"
#define ID     "ID"
#define END    "$END$"

#define cmember(ch, set) (strchr(set, ch) != NULL)// 測試字元 ch 是否在 set 當中
#define NEXT(var, tags)  char var[LEN];strcpy(var, token);next(tags)
#define SYMBOL(var, id)  char var[LEN];strcpy(var, symbol(id))
#define ASSERT(cond)     if (!(cond)) { ERROR(); }  // 要求條件要成立,否則就算錯

// 錯誤報告巨集函數,會印出哪一行呼叫了 ERROR()
#define ERROR() printf("ERROR => file:%s, line: %d\n", __FILE__, __LINE__);exit(1)

FILE *file;
char ch;
int line=1, pos=0;
char token[LEN], tag[LEN];
int  tokenIdx = 0;

typedef struct Sym {
    int strIdx;
} Sym;

int symTop = 1;
Sym symTable[SYM_TABLE_MAX];

char strTable[STR_TABLE_MAX];
int  strTop = 0;

int strFind(char *strList[], char *key) {
    int i;
    for (i=0; strList[i] != NULL; i++) {
        if (strcmp(strList[i], key)==0)
            return i;
    }
    return NIL;
}

void debug(const char *fmt, ...) {
    va_list args;
    va_start(args, fmt);
    vprintf(fmt, args);
}

char symTemp[LEN];

char *symbol(int s) {
    if (s == 0)
        return "";
    else if (s > 0)
        return &strTable[symTable[s].strIdx];
    else { // s < 0; temp variable
        sprintf(symTemp, "t%d", -1*s);
        return symTemp;
    }
}

int symFind(char *sym) {
    int i;
    for (i=1; i<symTop; i++) {
        if (strcmp(sym, symbol(i))==0)
            return i;
    }
    return NIL;
}

int symPut(char *sym) {
    int s = symFind(sym);
    if (s == NIL) {
        sprintf(&strTable[strTop], "%s", sym);
        s = symTop++;
        symTable[s].strIdx = strTop;
        strTop += strlen(sym) + 1;
    }
    return s;
}

void symTableDump() {
    int i;
    printf("======= symTable ========\n");
    for (i=1; i<symTop; i++) {
        printf("sym[%d]=%s\n", i, symbol(i));
    }
}

void strTableDump() {
    int i;
    printf("======= strTable ========\n");
    for (i=0; i<strTop; i++) {
        char c = strTable[i];
        if (c == '\0') 
            printf(".");
        else
            printf("%c", c);
    }
    printf("\n");
}

int labelIdx = 0;

int nextLabel() {
    char label[LEN];
    sprintf(label, "_L%d:", labelIdx++);
    return symPut(label);
}

int tempIdx = -1;

int nextTemp() {
    return tempIdx--;
}

char stack[100];
int top = 0;

void printStack() {
    int i;
    for (i=0; i<top; i++)
        printf("%c", stack[i]);
    printf("\n");
}

int push(char c) {
    stack[top++] = c;
//    printStack();
}

char pop(char c) {
    char ctop = stack[--top];
//    printStack();
    ASSERT(ctop==c);
    return ctop;
}

// 功能:檢查 token 是否為集合字串 set 中的元素
// 範例:strPartOf("int", "byte|int|float") 會傳回 TRUE
BOOL strPartOf(char *token, char *set) {
    ASSERT(token != NULL && set != NULL);
    ASSERT(strlen(token) < LEN);
    char ttoken[LEN+2];
    sprintf(ttoken, "|%s|", token);
    return (strstr(set, ttoken)!=NULL);
}

BOOL isNext(char *tags) { // 檢查下一個詞彙的型態
    char tTags[LEN+1];
    sprintf(tTags, "|%s|", tags);
    if (strPartOf(tag, tTags))
        return TRUE;
    else
        return FALSE;
}

char cnext() {
    token[tokenIdx++]=ch;
    pos++;
    ch=fgetc(file);
    return ch;
}

void tnext() {
    while (cmember(ch, SPACE)) { // 忽略空白
        tokenIdx = 0;
        if (ch=='\n') {
            line++;
            pos = 1;
        }
        cnext();
    }
    if (feof(file)) {
        strcpy(token, END);
        strcpy(tag, END);
        return;
    }
    tokenIdx = 0;
    if (ch == '\"') { // 如果是 " 代表字串開頭
        // 字串常數 : string = ".."
        cnext(); // 跳過 "
        while (ch != '\"') cnext(); // 一直讀到下一個 " 符號為止。
        cnext(); // 跳過 "
        strcpy(tag, STRING);
    } else if (cmember(ch, OP)) { // 如果是OP(+-*/<=>!等符號)
          // 運算符號 : OP = ++, --, <=, >=, ...
        while (cmember(ch, OP)) cnext(); // 一直讀到不是OP為止
        token[tokenIdx] = '\0';
        strcpy(tag, token);
    } else if (cmember(ch, DIGIT)) { // 如果是數字
           // 數字常數 : number = 312, 77568, ...
        while (cmember(ch, DIGIT)) cnext(); // 一直讀到不是數字為止
        strcpy(tag, NUMBER);
        // 浮點常數 : float = 3.14, ...
        if (ch == '.') {
            cnext(); // 取得小數點
            strcpy(tag, "FLOAT");
        }
        while (cmember(ch, DIGIT)) cnext(); // 取得小數部分
    } else if (cmember(ch, ALPHA)) { // 如果是英文字母
        // 基本詞彙 : token = int, sum, i, for, if, x1y2z, ....
        while (cmember(ch, ALPHA) || cmember(ch, DIGIT))
            cnext(); // 一直讀到不是英文字母 (或數字)為止
        token[tokenIdx] = '\0';
        if (strFind(keys, token)==NIL)
            strcpy(tag, ID);
        else
            strcpy(tag, token);
    } else { // 其他符號,都解讀為單一字元
        sprintf(tag, "%c", ch);
        cnext(); // 傳回單一字元
    }
    token[tokenIdx] = '\0';
//    printf("token=%s tag=%s\n", token, tag);
}

void next(char *tags) { // 檢查下一個詞彙的型態
    if (isNext(tags)) { // 如果是pTags型態之一
        tnext();
    } else { // 否則,印出錯誤訊息
        debug("next():line=%d pos=%d token=%s tag=%s, expect(%s)\n", line, pos, token, tag, tags); 
        printStack();
        ERROR();
    }
}

char *pcodeText = NULL;

void pcodeRedirect(char *text) {
    if (text != NULL)
        strcpy(text, "");
    pcodeText = text;
}

void pcodeDump(char *text) {
    printf("%s", text);
}

void pcode(int lab, char *op, int s, int s1, int s2) {
    char pcodeStr[LEN];
    SYMBOL(label, lab); SYMBOL(p, s); SYMBOL(p1, s1); SYMBOL(p2, s2);
    sprintf(pcodeStr, "%-8s %-8s %-8s %-8s %-8s\n", label, op, p, p1, p2);
    if (pcodeText == NULL)
        printf("%s", pcodeStr);
    else
        strcat(pcodeText, pcodeStr);
}

#define MAX_ARGS 100
int argList[MAX_ARGS];
int argTop = 0;

int argPush(int a) { argList[argTop++] = a; }
int argPop() { return argList[--argTop]; }

// ARGS = E? {,E}*
// 用在 ID(ARGS) 中,follow 為 )
int ARGS() {
    push('A');
    argTop = 0;
    if (!isNext(")")) {
        argPush(E());
        while (isNext(",")) {
            next(",");
            argPush(E());
        }
    }
    pop('A');
}

// F=STRING|NUMBER|ID ('('ARGS')')?|'(' E ')'
int F() {
    int f;
    push('F');
    if (isNext("(")) {
        next("(");
        f = E();
        next(")");
    } else if (isNext(NUMBER)) {
        NEXT(number, NUMBER);
        int n = symPut(number);
        f = nextTemp();
        pcode(0, "=", f, n, 0);
    } else if (isNext(STRING)) {
        NEXT(str, STRING);
        f=symPut(str);
    } else { // if (isNext(ID))
        NEXT(id, ID);
        f=symPut(id);
        if (isNext("(")) { // function call
            next("(");
            ARGS();
            next(")");
            int i;
            for (i=0; i<argTop; i++) {
                pcode(0, "ARG", argList[i], 0, 0);
            }
            int t = nextTemp();
            pcode(0, "CALL", f, t, 0);
            f = t;
        }
    }
    pop('F');
    return f; 
}

#define E_OP "+|-|*|/|%|&|^|||&&||||>>|<<|==|<=|>=|<|>"
// E=F (E_OP F)?
int E() {
    push('E');
    int f1 = F();
    if (isNext(E_OP)) {
        NEXT(op, E_OP);
        int f2 = F();
        int e = nextTemp();
        pcode(0, op, e, f1, f2);
        f1 = e;
    }
    pop('E');
    return f1;
}

// STMT=ID[++|--]| ID?=E | return E
int STMT() {
    push('S');
    if (isNext("return")) { 
        next("return");
        int e = E();
        pcode(0, "RET", e, 0, 0);
    } else {
        int var = NIL;
        if (isNext(ID)) {
            NEXT(id, ID);
            var = symPut(id);
        }
        if (isNext("++|--")) {
            NEXT(op1, "++|--");
            ASSERT(var != NIL);
            pcode(0, op1, var, 0, 0);
        } else { // if (isNext("="))
            next("=");
            int e = E();
            if (var != NIL)
                pcode(0, "=", var, e, 0);
        }
    }
    pop('S');
}

// BLOCK={ BASE* }
int BLOCK() {
    push('K');
    next("{");
    while (!isNext("}")) {
        BASE();
    }
    next("}");
    pop('K');
}

// BASE=STMT;|IF|WHILE|FOR|BLOCK
int BASE() {
    push('B');
    if (isNext("{"))
        BLOCK();
    else if (isNext("if"))
        IF();
    else if (isNext("while"))
        WHILE();
    else if (isNext("for"))
        FOR();
    else if (isNext("def"))
        DEF();
    else {
        STMT();
        next(";");
    }
    pop('B');
}

// IF=if (E) BASE else BASE
int IF() {
    push('I');
    next("if");
    next("(");
    int e = E();
    next(")");
    int elseLabel = nextLabel();
    pcode(0, "ifnot", e, elseLabel, 0);
    BASE();
    if (isNext("else")) {
        next("else");
        pcode(elseLabel, "", 0, 0, 0);
        BASE();
    }
    pop('I');
}

// WHILE=while (E) BASE
int WHILE() {
    push('W');
    int startLabel = nextLabel();
    int exitLabel = nextLabel();
    pcode(startLabel, "", 0, 0, 0);
    next("while");
    next("(");
    int e = E();
    next(")");
    pcode(0, "ifnot", e, exitLabel, 0);
    BASE();
    pcode(0, "goto", startLabel, 0, 0);
    pcode(exitLabel, "", 0, 0, 0);
    pop('W');
}

// FOR=for (STMT;E;STMT) BASE
int FOR() {
    push('F');
    int startLabel = nextLabel();
    int exitLabel = nextLabel();
    next("for");
    next("(");
    STMT();
    next(";");
    pcode(startLabel, "", 0, 0, 0);
    int e = E();
    pcode(0, "ifnot", e, exitLabel, 0);
    next(";");
    char setPcode[20*LEN];
    pcodeRedirect(setPcode);
    STMT(); // ? 這個不能邊比對邊編譯,怎麼辦?用 pipe 先轉向某 setPCode,然後在將結果補在下面。
    next(")");
    pcodeRedirect(NULL);
    BASE();
    pcodeDump(setPcode);
    pcode(0, "goto", startLabel, 0, 0);
    pcode(exitLabel, "", 0, 0, 0);
    pop('F');
}

// PARAMS = ID? {, ID}*
int PARAMS() {
    if (isNext(ID)) {
        NEXT(p1, ID);
        pcode(0, "PARAM", symPut(p1), 0, 0);
        while (isNext(",")) {
            next(",");
            NEXT(p2, ID);
            pcode(0, "PARAM", symPut(p2), 0, 0);
        }
    }
}

// DEF=def ID(PARAMS) BLOCK
int DEF() {
    push('D');
    int exitLabel = nextLabel();
    next("def");
    NEXT(id, ID);
    char fname[LEN];
    sprintf(fname, "_%s:", id);
    int f = symPut(fname);
    pcode(f, "function", 0, 0, 0);
    next("(");
    PARAMS();
    next(")");    
    BLOCK();
    pop('D');
}

// PROG=BASE*
int PROG() {
    push('P');
    while (!isNext(END)) {
        BASE();
    }
    pop('P');
}

int init() {
    fseek(file, 0, SEEK_SET);
    tokenIdx = 0;
    tnext();
}

int scan() {
    init();
    while (TRUE) {
        tnext();
        if (strcmp(token, END)==0)
            break;
        printf("%s\n", token);
    }
}

int compile(char *fname) {
    printf("==== compile file:%s ========\n", fname);
    file = fopen(fname, "r");
    init();
//  scan();
    PROG();
    symTableDump();
    strTableDump();
    fclose(file);
}

int main(int argc, char * argv[]) {
    char *fname = argv[1];
    compile(fname);
}

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