如何在yacc中使用递归来打印AST？

Question

我正在构建一个特定语言的编译器，我已经制作了一个lex扫描器和yacc Parser以及一些包含该语言的文本文件，目标是构建一个合适的AST并打印它，

我已经使用我需要的所有规则制作了完整的yacc和lex文件，我运行它们使用代码：

yacc -d test.y
lex test.l
cc -o test y.tab.c -ll -Ly
./test < file.t

这些文件能够从文本文件中创建解析器而不会出现任何语法问题，因此使用lex和yacc进行扫描和解析是有效的。

我已经为AST的构造准备了函数，要打印它我做了一个递归函数，按预先扫描以打印所有树。

*我删除了大部分不相关的代码

一些yacc代码：

%{
    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>

    typedef struct node {
        char* token;
        struct node *left;
        struct node *middle; 
        struct node *right;
    }node;



    node *mknode(char *token,node *left,node *middle,node *right);

    void printTree(node *tree);

    void yyerror(const char *s);

    int yylex();

    #define printTree

    #define YYSTYPE struct node*
    extern char *yytext;

%}
%start start
%token MULTI DIVISION BOOL CHAR INT REAL STRING INTPTR CHARPTR REALPTR IF ELSE WHILE FOR VAR FUNC PROC RETURN ASSIGN AND EQUAL GREATER GREATEREQUAL LESS LESSEQUAL MINUS NOT NOTEQUAL OR PLUS ADDRESS DEREFERENCE ABSUOLUT NULLL SEMICOLON COLUMS COMMA NEGATIVE_NUM LEFTBRACE RIGHTBRACE LEFTBRACKET RIGHTBRACKET COOMMENT PRESENT MAIN BOOLTRUE LEFTPAREN RIGHTPAREN BOOLFALSE INTEGER_CONST CHAR_CONST REAL_CONST ID STRING_CONST HEX_CONST 
%right ASSIGN ELSE DIVISION
%left LEFTBRACE RIGHTBRACE LEFTPAREN RIGHTPAREN
%left EQUAL GREATER GREATEREQUAL LESSEQUAL LESS NOTEQUAL
%left PLUS MINUS AND OR 
%left MULTI 

%%
    start: Main                {printTree($1);};

    Main: proc Main            {$$=mknode("CODE",$1,$2,NULL);}  
         |empty                {$$=mknode("CODE",$1,NULL,NULL);};


    id: ID                                               {$$=mknode(yytext,NULL,NULL,NULL);};


    leftParen: LEFTPAREN                                       {$$=mknode("(",NULL,NULL,NULL);};

    rightParen: RIGHTPAREN                                     {$$=mknode(")",NULL,NULL,NULL);};

    empty:                                               {$$=mknode("",NULL,NULL,NULL);};

    proc: PROC id leftParen paramsList rightParen Problock {$$=mknode("PROC",mknode($2->token,$3,$4,$5),NULL,$6);}
         |FUNC id leftParen paramsList rightParen returnInsideFuncDeclaration Problock {$$=mknode("FUNC",mknode($2->token,$3,$4,$5),$6,$7);};


    paramsList: startparamsList SEMICOLON paramsList     {$$=mknode("start_params",$1,mknode(";",NULL,NULL,NULL),$3);}
                |startparamsList                         {$$=mknode("start_params",$1,NULL,NULL);}
                |empty                                   {$$=mknode("start_params",$1,NULL,NULL);}; 

    startparamsList: id next_param_in_proc               {$$=mknode("start_params",$1,$2,NULL);};

    next_param_in_proc: COMMA id next_param_in_proc      {$$=mknode(",",$2,$3,NULL);}
                        |COLUMS varType                  {$$=mknode(":",$2,NULL,NULL);};



    Problock: leftBrace Procbody rightBrace              {$$=mknode("PROC",$1,$2,$3);};

    Procbody: BlockBody                                  {$$=mknode("BODY",$1,NULL,NULL);}
              |BlockBody return                          {$$=mknode("BODY",$1,$2,NULL);} ; 


    HelpToStatement: ProcStatement HelpToStatement       {$$=mknode("help to statment",$1,$2,NULL);}
                     |empty                              {$$=mknode("help to statment",$1,NULL,NULL);};

    HelpToTheProcedure: proc HelpToTheProcedure          {$$=mknode("help proc",$1,$2,NULL);}
                        |empty                           {$$=mknode("help proc",$1,NULL,NULL);};

    HelpDeclare: Declaration HelpDeclare                 {$$=mknode("declartion",$1,$2,NULL);}
                 |empty                                  {$$=mknode("declartion",$1,NULL,NULL);};

    BlockBody: HelpToTheProcedure HelpDeclare HelpToStatement   {$$=mknode("Body",$1,$2,$3);};   


    ProcStatement:   exp SEMICOLON 
                     |structOfCond
                     |block;

%%
#include "lex.yy.c"

int main()
{
    return yyparse();
}

node *mknode(char *token, node *left, node *middle, node *right)
{
    node *newnode = (node*)malloc(sizeof(node));
    char *newstr = (char*)malloc(sizeof(token)+1);
    strcpy(newstr,token);
    newnode->left = left;
    newnode->middle = middle;
    newnode->right = right;
    newnode->token = newstr;
    return newnode;
}
void printtree(node *tree)
{
    printf("%s\n",tree->token);
    if(tree->left)
        printtree(tree->left);
    if(tree->middle)
        printtree(tree->middle);
    if(tree->right)
        printtree(tree->right);
}

void yyerror(const char *str)
{
    printf("%s - %s in line:%d \n",str,yytext,counter);
}

所以我设法从语言中构建AST，但不打印它，因为某些原因函数'printTree'什么也没做，

如果我尝试像这样打印：printf("%s", $1->token)或printf("%s", $1->left->token)，那么一切都很好，每个令牌都在它的合法位置，那么为什么我不能使用递归函数打印它们？

Answer 1

你用printTree定义#define printTree什么都不是。所以printTree($1);被宏观扩展到($1);，这是一个无操作。另一方面，你的函数printtree（没有大写字母）永远不会被调用。

所以你应该删除#define，向前声明printtree函数，然后在你的动作中调用它。