编译器的语法分析.docx

1、编译器的语法分析佛山科学技术学院 实 验 报 告课程名称 编译原理 实验项目 编译器的语法分析 专业班级 计算机1班 姓 名 学 号 指导教师 黄营 成 绩 日 期 2014/6/7 一、实验目的； 掌握PL语言编译器的语法分析程序设计与LL（1）文法应用的实现方法。二、实验内容；采用递归下降的方法来设计PL/0编译器，证明PL/0语言属于LL（1）文法。然后结合语法图编写（递归下降）语法分析程序的一般方法，具体方面有：（1）用合适的替换将语法约化成尽可能少的单个图；（2）将每一个图按下面的规则（3）-（7）翻译成一个过程说明；（3）顺序图对应复合语句：对应：begin T(S1); T(S2

2、); .; T(Sn) end（4）选择： 对应：case语句或者条件语句： case ch of if ch in L1 then T(S1) else L1: T(S1); if ch in L2 then T(S2) else L2: T(S2); 或 . if ch in Ln then T(Sn) elseLn: T(Sn); error 其中LiFIRST（Si），ch为当前输入符号。（下同）（5）循环： 对应：while ch in L do T(S)（6）表示另一个图A的图：对应：过程调用A。（7）表示终结符的单元图：对应：if ch = x then read(ch) els

3、e error相关过程有：block(), constdeclaration(), vardeclaration(), statement(), condition(), expression(), term(), factor()等。并画出它们之间依赖关系图，并在此基础上实现程序的编制。并适当进行语义分析的相关检查：（1）是否存在标识符先引用未声明的情况；（2）是否存在己声明的标识符的错误引用；（3）是否存在一般标识符的多重声明。三、实验步骤； 1. 将实验一“词法分析”的输出结果，作为表达式语法分析器的输入，进行语法解析，对于语法正确的表达式，报告“语法正确”；并指出该语句属于哪一条文法。

4、 对于语法错误的表达式，报告“语法错误”， 指出错误原因。 2. 把语法分析器设计成一个独立一遍的过程。 3. 语法分析器的编写方法采用递归子程序法。四、程序代码；set.h：#ifndef SET_H#define SET_Htypedef struct snode int elem; struct snode* next; snode, *symset;symset phi, declbegsys, statbegsys, facbegsys, relset;symset createset(int data, ./* SYM_NULL */);void destroyset(symset

5、 s);symset uniteset(symset s1, symset s2);int inset(int elem, symset s);void showset(symset s);#endif/ EOF set.hpl0.h:#include #define NRW 11 / number of reserved words#define TXMAX 500 / length of identifier table#define MAXNUMLEN 14 / maximum number of digits in numbers#define NSYM 10 / maximum nu

6、mber of symbols in array ssym and csym#define MAXIDLEN 10 / length of identifiers#define MAXADDRESS 32767 / maximum address#define MAXLEVEL 32 / maximum depth of nesting block#define CXMAX 500 / size of code array#define MAXSYM 30 / maximum number of symbols #define STACKSIZE 1000 / maximum storagee

7、num symtype SYM_NULL, / 0 SYM_IDENTIFIER, / 1 SYM_NUMBER, / 2 SYM_PLUS, / 3 + SYM_MINUS, / 4 - SYM_TIMES, / 5 * SYM_SLASH, / 6 / SYM_ODD, / 7 odd SYM_EQU, / 8 = SYM_NEQ, / 9 - SYM_LES, / 10 SYM_LEQ, / 11 SYM_GEQ, / 13 = SYM_LPAREN, / 14 ( SYM_RPAREN, / 15 ) SYM_COMMA, / 16 , SYM_SEMICOLON, / 17 ; SY

8、M_PERIOD, / 18 . SYM_BECOMES, / 19 := SYM_BEGIN, / 20 begin SYM_END, / 21 end SYM_IF, / 22 if SYM_THEN, / 23 then SYM_WHILE, / 24 while SYM_DO, / 25 do SYM_CALL, / 26 call SYM_CONST, / 27 const SYM_VAR, / 28 var SYM_PROCEDURE / 29 procedure;enum idtype ID_CONSTANT, ID_VARIABLE, ID_PROCEDURE;enum opc

9、ode LIT, OPR, LOD, STO, CAL, INT, JMP, JPC;enum oprcode OPR_RET, OPR_NEG, OPR_ADD, OPR_MIN, OPR_MUL, OPR_DIV, OPR_ODD, OPR_EQU, OPR_NEQ, OPR_LES, OPR_LEQ, OPR_GTR, OPR_GEQ;typedef struct int f; / function code int l; / level int a; / displacement address instruction;/char* err_msg =/* 0 */ ,/* 1 */

10、Found := when expecting =.,/* 2 */ There must be a number to follow =.,/* 3 */ There must be an = to follow the identifier.,/* 4 */ There must be an identifier to follow const, var, or procedure.,/* 5 */ Missing , or ;.,/* 6 */ Incorrect procedure name.,/* 7 */ Statement expected.,/* 8 */ Follow the

11、 statement is an incorrect symbol.,/* 9 */ . expected.,/* 10 */ ; expected.,/* 11 */ Undeclared identifier.,/* 12 */ Illegal assignment.,/* 13 */ := expected.,/* 14 */ There must be an identifier to follow the call.,/* 15 */ A constant or variable can not be called.,/* 16 */ then expected.,/* 17 */

12、; or end expected.,/* 18 */ do expected.,/* 19 */ Incorrect symbol.,/* 20 */ Relative operators expected.,/* 21 */ Procedure identifier can not be in an expression.,/* 22 */ Missing ).,/* 23 */ The symbol can not be followed by a factor.,/* 24 */ The symbol can not be as the beginning of an expressi

13、on.,/* 25 */ The number is too great.,/* 26 */ Redeclared identifier., / added by yzhang 02-02-28/* 27 */ ,/* 28 */ ,/* 29 */ ,/* 30 */ ,/* 31 */ ,/* 32 */ There are too many levels.;/char ch; / last character readint sym; / last symbol readchar idMAXIDLEN + 1; / last identifier readint num; / last

14、number readint cc; / character countint ll; / line lengthint kk;int err;int cx; / index of current instruction to be generated.int level = 0;int tx = 0;char line80;instruction codeCXMAX;char* wordNRW + 1 = , /* place holder */ begin, call, const, do, end,if, odd, procedure, then, var, while;int wsym

15、NRW + 1 = SYM_NULL, SYM_BEGIN, SYM_CALL, SYM_CONST, SYM_DO, SYM_END, SYM_IF, SYM_ODD, SYM_PROCEDURE, SYM_THEN, SYM_VAR, SYM_WHILE;int ssymNSYM + 1 = SYM_NULL, SYM_PLUS, SYM_MINUS, SYM_TIMES, SYM_SLASH, SYM_LPAREN, SYM_RPAREN, SYM_EQU, SYM_COMMA, SYM_PERIOD, SYM_SEMICOLON;char csymNSYM + 1 = , +, -,

16、*, /, (, ), =, , ., ;#define MAXINS 8char* mnemonicMAXINS = LIT, OPR, LOD, STO, CAL, INT, JMP, JPC;typedef struct char nameMAXIDLEN + 1; int kind; int value; comtab;comtab tableTXMAX;typedef struct char nameMAXIDLEN + 1; int kind; short level; short address; mask;FILE* infile, *outfile;/ EOF PL0.hse

17、t.c:#include #include #include #include set.hsymset uniteset(symset s1, symset s2) symset s; snode* p; s = p = (snode*) malloc(sizeof(snode); / added by yzhang 02-02-28 s1 = s1-next; s2 = s2-next; / end add while (s1 & s2) p-next = (snode*) malloc(sizeof(snode); p = p-next; if (s1-elem elem) p-elem

18、= s1-elem; s1 = s1-next; else p-elem = s2-elem; s2 = s2-next; if ( s2 ) s1 = s2; /added by yzhang 02-02-28 while (s1) p-next = (snode*) malloc(sizeof(snode); p = p-next; p-elem = s1-elem; s1 = s1-next; /* deleted by yzhang 02-02-28 while (s2) p-next = (snode*) malloc(sizeof(snode); p = p-next; p-ele

19、m = s2-elem; s2 = s2-next; */ p-next = NULL; return s; / unitesetvoid setinsert(symset s, int elem) snode* p = s; snode* q; while (p-next & p-next-elem next; q = (snode*) malloc(sizeof(snode); q-elem = elem; q-next = p-next; p-next = q; / setinsertsymset createset(int elem, ./* SYM_NULL */) va_list

20、list; symset s; s = (snode*) malloc(sizeof(snode); s-next = NULL; va_start(list, elem); while (elem) setinsert(s, elem); elem = va_arg(list, int); va_end(list); return s; / createsetvoid destroyset(symset s) snode* p; while (s) p = s; s = s-next; free(p); / destroysetint inset(int elem, symset s) s

21、= s-next; while (s & s-elem next; if (s & s-elem = elem) return 1; else return 0; / inset/added by yzhang 02-02-28void showset(symset s) s = s-next; while (s ) printf(%d, s-elem); s = s-next; printf(n); / showset/ EOF set.cpl0.c: / pl0 compiler source code#include #include #include #include #include

22、 set.h#include pl0.h/ print error message.void error(int n) int i; printf( ); for (i = 1; i = cc - 1; i+) printf( ); fprintf(outfile, ); fprintf(outfile, n); printf(n); fprintf(outfile, Error %3d: %sn, n, err_msgn); printf(Error %3d: %sn, n, err_msgn); err+; / error/void getch(void) if (cc = ll) if

23、(feof(infile) printf(nPROGRAM INCOMPLETEn); exit(1); ll = cc = 0; fprintf(outfile, %5d , cx); printf(%5d , cx); while ( (!feof(infile) / added & modified by alex 01-02-09 & (ch = getc(infile) != n) fprintf(outfile, %c, ch); printf(%c, ch); line+ll = ch; / while fprintf(outfile, n); printf(n); line+l

24、l = ; ch = line+cc; / getch/ gets a symbol from input stream.void getsym(void) int i, k; char aMAXIDLEN + 1; while (ch = | ch = t) / modified by yzhang 02-03-12,add some white space getch(); if (isalpha(ch) / symbol is a reserved word or an identifier. k = 0; do if (k MAXNUMLEN) error(25); / The number is too great. else if (ch = :) getch(); if (ch = =) sym = SYM_BECOMES; / := getch(); else sym = SYM_NULL; / illegal? else if (ch = ) getch(); if (ch = =) sym = SYM_GEQ; / = getch(); else sym = SYM_GTR; / else if (ch = ) getch();