Simple lex/yacc converter from pseudo C to pseudo assemlby language

Question

Had to repeat question to provide answer

I would like to make some kind of translator from mini C to NASM (assembly) using YACC/LEX (c++) Program should recive part of code and return file with that part in NASM assembly

mini C should support code like this one

a = v1;
b = v2;
while(condition){
    // Some expressions +
}
if(Condition){ //
// Some expressions + 
else{
// Some expressions +
}

It should recognize positive int values, only simple expressions + ,if/else and while loop with conditions {<,>,==} I know how to do lexical analysis part using flex but parser is troublesome for me especially parsing while loop and if/else.

Those if/else and while parts can have begin/end instead of {}

I guess grammar should be like

Program: Block '.' 
;

Block : BEGIN_TOKEN Lines END_TOKEN
;

Lines: Lines ';' Line
| Line
;

Line: INT_TOKEN ID_TOKEN '=' NUM_TOKEN
| IF_TOKEN '(' Condition ')' Block ELSE Block
| WHILE_TOKEN '(' Condition ')' Block
| E
;

E: E + E
| ID_TOKEN
| NUM_TOKEN
;

Conditon: E '<' E
| E '>' E
| E EQ_TOKEN E
;

Conditions are simple ones like a<5 , b>c , d==3... It doesn't need to have any kind of prints and scans Actions should be written in separate c++ file

Answer 1

Because my last question was closed because someone though that I am writing book, I would like to share my solution to this problem. This problem was my homework.

lexer.l

%option noyywrap
%option nounput
%option noinput

%{
    
    #include <iostream>
    #include <cstdlib>
    
    using namespace std;
    
    #include "parser.tab.hpp"
    
%}

%%

while           {return WHILE_TOKEN;}
if              {return IF_TOKEN;}
else            {return ELSE_TOKEN;}
print           {return PRINT_TOKEN;}
"=="            {return EQ_TOKEN;}
"<="            {return LEQ_TOKEN;}
">="            {return GEQ_TOKEN;}
[-+(){}<>=;]    {return *yytext;}
[a-z]           {yylval.s = new string(yytext); return ID_TOKEN;}
(0|[1-9][0-9]*) {yylval.s = new stirng(yytext); return NUM_TOKEN;}
[ \t\n]         {}
.               {cerr<<"Lex error:  "<< *yytext << endl; exit(EXIT_FAILURE);}
%%

parser.ypp

%{

#include <ostream>
#include <fstream>
#include <cstdlib>
#include <string>


using namespace std;

void yyerror(string s){
    cerr << s << endl;
    exit(EXIT_FAILURE);
}

extern int yylex();

ofstream out;

int next_label = 0;

%}

%union{
    string *s;
    int v;
}

%nonassoc IF_THEN
%nonassoc ELSE_TOKEN

%right '='
%left '<' '>' EQ_TOKEN LEQ_TOKEN GEQ_TOKEN
%left '+' '-'

%type<s> ID_TOKEN NUM_TOKEN
%type<v> WHILE_TOKEN IF_TOKEN ELSE_TOKEN
%token PRINT_TOKEN EQ_TOKEN LEQ_TOKEN GEQ_TOKEN WHILE_TOKEN ELSE_TOKEN IF_TOKEN ID_TOKEN NUM_TOKEN

%%

Program: Statements {out << "" << endl;}
;

Statements: Statements Statement {}
|
;

Statement: ';'
| E ';'
| '{' Statements '}'
| ID_TOKEN '=' E ';' {out << "assign_val" << endl;}
| PRINT_TOKEN '(' E ')' {out << "print" << endl;}
| WHILE_TOKEN {$1 = next_label; out << "L:" << $1 << ":" << endl; next_label+=2;} '(' E ')' {out << "L" << $1 +1 << ":" << endl;} Statement
| IF_TOKEN '(' E ')' {$1 = next_label++; out << "L" << $1 << ":" << endl;} Statement Else
;

Else: ELSE_TOKEN {$1 = next_label++; out << "jmp L" << $1 << ":" << endl;} Statement {out << "L" << $1 << ":" << endl;}
| %prec IF_THEN {}
;

E: E '+' E {out << "add" << endl;}
| E '-' E {out << "sub" << endl;}
| E '<' E {out << "compL" << endl;}
| E '>' E {out << "compG" << endl;}
| E EQ_TOKEN E {out << "compEQ" << endl;}
| E LEQ_TOKEN E {out << "compLEQ" << endl;}
| E GEQ_TOKEN E {out << "compGEQ" << endl;}
| '(' E ')'
| ID_TOKEN {out << *$1 << endl;}
| NUM_TOKEN {out << *$1 << endl;}
;

%%

int main(){
    out.open("output.s", ios_base::app);
    yyparse();
    return 0;
}

makefile

program: parser.tab.o lex.yy.o
    g++ -Wall -o $@ $^
parser.tab.o: parser.tab.cpp parser.tab.hpp
    g++ -Wall -c -o $@ $<
lext.yy.o: lex.yy.c
    g++ -Wall -c -o $@ $<
lex.yy.c: lexer.l parser.tab.hpp
    flex $<
parser.tab.cpp parser.tab.hpp: parser.ypp
    bison -d -v $<

Locate directory with source files in terminal and just run make command