├── .clang-format ├── .gitignore ├── assets ├── steps_dark.jpg └── steps_light.jpg ├── examples ├── simple_c_examples │ ├── example1.c │ └── example2.c ├── simple_c_mips_examples │ ├── example.c │ ├── example2.c │ ├── example.s │ ├── example2.s │ ├── full_example.c │ └── full_example.s └── bison_example │ └── calc.y ├── src ├── compiler.c ├── lexer.l ├── parser.y └── symtab.c ├── Makefile ├── include └── symtab.h ├── README.md ├── docs └── articles.md └── LICENSE /.clang-format: -------------------------------------------------------------------------------- 1 | IndentWidth: 4 2 | TabWidth: 4 3 | UseTab: Never 4 | 5 | -------------------------------------------------------------------------------- /.gitignore: -------------------------------------------------------------------------------- 1 | *.o 2 | *.a 3 | *.la 4 | *.lo 5 | *.out 6 | 7 | build/ 8 | bin/ 9 | -------------------------------------------------------------------------------- /assets/steps_dark.jpg: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/drifter1/compiler/HEAD/assets/steps_dark.jpg -------------------------------------------------------------------------------- /assets/steps_light.jpg: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/drifter1/compiler/HEAD/assets/steps_light.jpg -------------------------------------------------------------------------------- /examples/simple_c_examples/example1.c: -------------------------------------------------------------------------------- 1 | int i; 2 | double val = 2.5; 3 | for(i = 0; i < 10; i++){ 4 | val = val*i + i; 5 | } 6 | print(val); 7 | return; 8 | -------------------------------------------------------------------------------- /examples/simple_c_mips_examples/example.c: -------------------------------------------------------------------------------- 1 | // main function 2 | // declarations 3 | int i; 4 | double val, res; 5 | // statements 6 | val = 2.5; 7 | res = val + 1; 8 | return; 9 | -------------------------------------------------------------------------------- /examples/simple_c_examples/example2.c: -------------------------------------------------------------------------------- 1 | // main function 2 | // declarations 3 | int i; 4 | double val =2.5, res[10]; 5 | // statements 6 | for(i = 0; i < 10; i++){ 7 | res[i] = operation(val, i); 8 | val = res[i]; 9 | print(res[i]); 10 | print('\n'); 11 | } 12 | return; 13 | // functions 14 | double operation (double value, int i){ /* function declaration */ 15 | // declarations 16 | double res; 17 | // statements 18 | res = value*i + i; 19 | return res; 20 | } 21 | -------------------------------------------------------------------------------- /examples/simple_c_mips_examples/example2.c: -------------------------------------------------------------------------------- 1 | // main function 2 | // declarations 3 | int i; 4 | double val = 2.5, res[10]; 5 | // statements 6 | for(i = 0; i < 10; i++){ 7 | res[i] = operation(val, i); 8 | val = res[i]; 9 | print(res[i]); 10 | print('\n'); 11 | } 12 | return; 13 | // functions 14 | double operation (double value, int i){ /* function declaration */ 15 | // declarations 16 | double res; 17 | // statements 18 | res = value*i + i; 19 | return res; 20 | } 21 | -------------------------------------------------------------------------------- /examples/simple_c_mips_examples/example.s: -------------------------------------------------------------------------------- 1 | .data 2 | i: .word 0 3 | val: .space 8 # $f0 4 | res: .space 8 # $f2 5 | newline: .asciiz "\n" 6 | 7 | .text 8 | main: 9 | 10 | # val = 2.5 11 | li.d $f0, 2.5 12 | s.d $f0, val 13 | 14 | # res = val + 1 15 | li.d $f4, 1.0 16 | add.d $f2, $f0, $f4 17 | s.d $f2, res 18 | 19 | # print values for testing 20 | li $v0, 3 21 | mov.d $f12, $f0 22 | syscall 23 | 24 | li $v0, 4 25 | la $a0, newline 26 | syscall 27 | 28 | li $v0, 3 29 | mov.d $f12, $f2 30 | syscall 31 | 32 | # terminate program 33 | li $v0, 10 34 | syscall 35 | -------------------------------------------------------------------------------- /src/compiler.c: -------------------------------------------------------------------------------- 1 | #include "../include/symtab.h" 2 | #include 3 | 4 | extern FILE *yyin; 5 | extern FILE *yyout; 6 | extern int lineno; 7 | 8 | int yylex(); 9 | int yyparse(); 10 | 11 | int main(int argc, char *argv[]) { 12 | 13 | // initialize symbol table 14 | init_hash_table(); 15 | 16 | // parsing 17 | int flag; 18 | yyin = fopen(argv[1], "r"); 19 | flag = yyparse(); 20 | fclose(yyin); 21 | 22 | // symbol table dump 23 | yyout = fopen("symtab_dump.out", "w"); 24 | symtab_dump(yyout); 25 | fclose(yyout); 26 | 27 | return flag; 28 | } 29 | -------------------------------------------------------------------------------- /examples/bison_example/calc.y: -------------------------------------------------------------------------------- 1 | %{ 2 | #include 3 | #include 4 | void yyerror(char const*s) 5 | { 6 | fprintf(stderr,"%s\n",s); 7 | } 8 | %} 9 | %token DIGIT 10 | %% 11 | line : expr '\n' { printf ("%d\n" , $1 ) ; } 12 | expr : expr '+' term { $$ = $1 + $3 ; } 13 | | term 14 | ; 15 | term : term '*' factor { $$ = $1 * $3 ; } 16 | | factor 17 | ; 18 | factor : '(' expr ')' { $$ = $2 ; } 19 | | DIGIT 20 | ; 21 | %% 22 | yylex( ){ 23 | int c; 24 | c = getchar( ) ; 25 | if (isdigit(c ) ) { 26 | yylval= c - '0'; 27 | return DIGIT ; 28 | } 29 | return c ; 30 | } 31 | int yyparse(void); 32 | int main ( ) { 33 | return yyparse( ) ; 34 | } 35 | -------------------------------------------------------------------------------- /Makefile: -------------------------------------------------------------------------------- 1 | CC := gcc 2 | LEX := flex 3 | YACC := bison 4 | MKDIR_P := mkdir -p 5 | 6 | SRC_DIR := src 7 | BIN_DIR := bin 8 | OBJ_DIR := build 9 | 10 | LEX_SRC := $(SRC_DIR)/lexer.l 11 | YACC_SRC := $(SRC_DIR)/parser.y 12 | C_SRC := $(wildcard $(SRC_DIR)/*.c) 13 | 14 | LEX_OUT := $(OBJ_DIR)/lex.yy.c 15 | YACC_OUT := $(OBJ_DIR)/parser.tab.c 16 | 17 | TARGET := $(BIN_DIR)/compiler 18 | 19 | all: $(TARGET) 20 | 21 | $(TARGET): $(YACC_OUT) $(LEX_OUT) | $(BIN_DIR) 22 | @$(CC) -o $@ $(YACC_OUT) $(LEX_OUT) $(C_SRC) 23 | 24 | $(LEX_OUT): $(LEX_SRC) | $(OBJ_DIR) 25 | @$(LEX) -o $@ $< 26 | 27 | $(YACC_OUT): $(YACC_SRC) | $(OBJ_DIR) 28 | @$(YACC) -o $@ -d $< 29 | 30 | $(BIN_DIR): 31 | @$(MKDIR_P) $@ 32 | 33 | $(OBJ_DIR): 34 | @$(MKDIR_P) $@ 35 | 36 | clean: 37 | @rm -rf $(BIN_DIR) $(OBJ_DIR) 38 | 39 | .PHONY: all clean 40 | -------------------------------------------------------------------------------- /examples/simple_c_mips_examples/example2.s: -------------------------------------------------------------------------------- 1 | .data 2 | i: .word 0 # $f4 as FP 3 | val: .space 8 # $f2 4 | res: .space 80 # array with 10 doubles 5 | newline: .asciiz "\n" 6 | 7 | .text 8 | main: 9 | 10 | # val = 2.5 11 | li.d $f2, 2.5 12 | s.d $f2, val 13 | 14 | # for loop 15 | li $t0, 0 # i = 0 16 | li $t1, 0 # address counter 17 | li $t2, 10 # exit condition 18 | for: bge $t0, $t2, end_for # i < 10 19 | # temp = operation(val, i) 20 | # val in $f2 21 | # i in $t0 22 | jal operation 23 | 24 | # res[i] = temp 25 | s.d $f0, res($t1) 26 | 27 | # val = res[i] 28 | mov.d $f2, $f0 29 | s.d $f2, val($0) 30 | 31 | # print(res[i]) 32 | li $v0, 3 33 | mov.d $f12, $f0 34 | syscall 35 | 36 | # print("\n") 37 | li $v0, 4 38 | la $a0, newline 39 | syscall 40 | 41 | # i++ 42 | addi $t0, $t0, 1 43 | addi $t1, $t1, 4 44 | j for 45 | end_for: 46 | 47 | # terminate program 48 | li $v0, 10 49 | syscall 50 | 51 | operation: 52 | # convert int to double 53 | mtc1.d $t0, $f4 54 | cvt.d.w $f4, $f4 55 | # $f4 contains i 56 | 57 | # res = value*i + i 58 | mul.d $f0, $f2, $f4 59 | add.d $f0, $f0, $f4 60 | 61 | # return value in $f0 62 | jr $ra 63 | 64 | -------------------------------------------------------------------------------- /examples/simple_c_mips_examples/full_example.c: -------------------------------------------------------------------------------- 1 | // program: declarations statements RETURN SEMI functions 2 | // main function (declarations statements) 3 | // declarations 4 | int i; // simple variable 5 | char c = 'c'; // one with init 6 | double val = 2.5, res[6]; // two variables, one with init and one array 7 | double *p; // pointer variable 8 | // statements 9 | p = &res; // assigment 10 | for(i = 0; i < 10; i++){ // for 11 | if(i > 5){ // if-else 12 | break; 13 | } 14 | else if(i == 5){ 15 | i = 2 * i; 16 | val = func1(); 17 | *p = add(val, i); 18 | print(res[i]); 19 | print("\n"); 20 | continue; 21 | } 22 | else{ 23 | *p = add(val, i); 24 | val = res[i]; 25 | print(res[i]); 26 | print("\n"); 27 | p = p + 1; 28 | } 29 | 30 | if(i == 2 && val == 4.5){ // if 31 | print("iteration: 3\n"); 32 | } 33 | } 34 | 35 | while(i < 12){ // while 36 | print(i); 37 | print(" "); 38 | func2(c); 39 | i++; 40 | } 41 | print("\n"); 42 | return; /* RETURN SEMI */ 43 | // other functions (functions) 44 | int func1(){ /* without parameters */ 45 | // statements 46 | return 5; 47 | } 48 | void func2(char c){ /* with one parameter */ 49 | // declarations 50 | char *s; 51 | // statements 52 | *s = c; 53 | print(*s); 54 | } 55 | double add (double a, int b){ /* with two parameters */ 56 | // declarations 57 | double res; 58 | // statements 59 | res = a + b + (-5); 60 | return res; 61 | } 62 | -------------------------------------------------------------------------------- /include/symtab.h: -------------------------------------------------------------------------------- 1 | #include 2 | 3 | /* maximum size of hash table */ 4 | #define SIZE 211 5 | 6 | /* maximum size of tokens-identifiers */ 7 | #define MAXTOKENLEN 40 8 | 9 | /* token types */ 10 | #define UNDEF 0 11 | #define INT_TYPE 1 12 | #define REAL_TYPE 2 13 | #define STR_TYPE 3 14 | #define LOGIC_TYPE 4 15 | #define ARRAY_TYPE 5 16 | #define FUNCTION_TYPE 6 17 | 18 | /* how parameter is passed */ 19 | #define BY_VALUE 1 20 | #define BY_REFER 2 21 | 22 | /* current scope */ 23 | extern int cur_scope; 24 | 25 | /* parameter struct */ 26 | typedef struct Param { 27 | int par_type; 28 | char param_name[MAXTOKENLEN]; 29 | // to store value 30 | int ival; 31 | double fval; 32 | char *st_sval; 33 | int passing; // value or reference 34 | } Param; 35 | 36 | /* a linked list of references (lineno's) for each variable */ 37 | typedef struct RefList { 38 | int lineno; 39 | struct RefList *next; 40 | int type; 41 | } RefList; 42 | 43 | // struct that represents a list node 44 | typedef struct list_t { 45 | char st_name[MAXTOKENLEN]; 46 | int st_size; 47 | int scope; 48 | RefList *lines; 49 | // to store value and sometimes more information 50 | int st_ival; 51 | double st_fval; 52 | char *st_sval; 53 | // type 54 | int st_type; 55 | int inf_type; // for arrays (info type) and functions (return type) 56 | // array stuff 57 | int *i_vals; 58 | double *f_vals; 59 | char **s_vals; 60 | int array_size; 61 | // function parameters 62 | Param *parameters; 63 | int num_of_pars; 64 | // pointer to next item in the list 65 | struct list_t *next; 66 | } list_t; 67 | 68 | /* the hash table */ 69 | static list_t **hash_table; 70 | 71 | // Function Declarations 72 | void init_hash_table(); // initialize hash table 73 | unsigned int hash(char *key); // hash function 74 | void insert(char *name, int len, int type, int lineno); // insert entry 75 | list_t *lookup(char *name); // search for entry 76 | list_t *lookup_scope(char *name, int scope); // search for entry in scope 77 | void hide_scope(); // hide the current scope 78 | void incr_scope(); // go to next scope 79 | void symtab_dump(FILE *of); // dump file 80 | -------------------------------------------------------------------------------- /src/lexer.l: -------------------------------------------------------------------------------- 1 | %option noyywrap 2 | 3 | %{ 4 | #include "../include/symtab.h" 5 | #include "../build/parser.tab.h" 6 | 7 | int lineno = 1; // initialize to 1 8 | 9 | void ret_print(char *token_type); 10 | void yyerror(char *message); 11 | %} 12 | 13 | %x ML_COMMENT 14 | 15 | alpha [a-zA-Z] 16 | digit [0-9] 17 | alnum {alpha}|{digit} 18 | print [ -~] 19 | 20 | ID {alpha}+{alnum}* 21 | ICONST "0"|[0-9]{digit}* 22 | FCONST "0"|{digit}*"."{digit}+ 23 | CCONST (\'{print}\')|(\'\\[nftrbv]\') 24 | STRING \"{print}*\" 25 | 26 | %% 27 | 28 | "//".* { printf("Eat up comment at line %d\n", lineno); } 29 | 30 | "/*" { printf("Eat up comment from line %d ", lineno); BEGIN(ML_COMMENT); } 31 | "*/" { printf("to line %d\n", lineno); BEGIN(INITIAL); } 32 | [^*\n]+ 33 | "*" 34 | "\n" { lineno += 1; } 35 | 36 | 37 | "char"|"CHAR" { return CHAR; } 38 | "int"|"INT" { return INT; } 39 | "float"|"FLOAT" { return FLOAT; } 40 | "double"|"DOUBLE" { return DOUBLE; } 41 | "if"|"IF" { return IF; } 42 | "else"|"ELSE" { return ELSE; } 43 | "while"|"WHILE" { return WHILE; } 44 | "for"|"FOR" { return FOR; } 45 | "continue"|"CONTINUE" { return CONTINUE; } 46 | "break"|"BREAK" { return BREAK; } 47 | "void"|"VOID" { return VOID; } 48 | "return"|"RETURN" { return RETURN; } 49 | 50 | 51 | "+"|"-" { return ADDOP; } 52 | "*" { return MULOP; } 53 | "/" { return DIVOP; } 54 | "++"|"--" { return INCR; } 55 | "||" { return OROP; } 56 | "&&" { return ANDOP; } 57 | "!" { return NOTOP; } 58 | "=="|"!=" { return EQUOP; } 59 | ">"|"<"|">="|"<=" { return RELOP; } 60 | 61 | 62 | "(" { return LPAREN; } 63 | ")" { return RPAREN; } 64 | "[" { return LBRACK; } 65 | "]" { return RBRACK; } 66 | "{" { return LBRACE; } 67 | "}" { return RBRACE; } 68 | ";" { return SEMI; } 69 | "." { return DOT; } 70 | "," { return COMMA; } 71 | "=" { return ASSIGN; } 72 | "&" { return REFER; } 73 | 74 | 75 | {ID} { 76 | // insert identifier into symbol table 77 | insert(yytext, strlen(yytext), UNDEF, lineno); 78 | yylval.symtab_item = lookup(yytext); 79 | return ID; 80 | } 81 | {ICONST} { yylval.int_val = atoi(yytext); return ICONST; } 82 | {FCONST} { yylval.double_val = atof(yytext); return FCONST; } 83 | {CCONST} { yylval.char_val = yytext[0]; return CCONST; } 84 | {STRING} { 85 | yylval.str_val = malloc(yyleng * sizeof(char)); 86 | strcpy(yylval.str_val, yytext); return STRING; 87 | } 88 | 89 | 90 | "\n" { lineno += 1; } 91 | [ \t\r\f]+ /* eat up whitespace */ 92 | 93 | . { yyerror("Unrecognized character"); } 94 | 95 | %% 96 | -------------------------------------------------------------------------------- /examples/simple_c_mips_examples/full_example.s: -------------------------------------------------------------------------------- 1 | .data 2 | # variables 3 | i: .word 0 # int i 4 | val: .space 8 # double val in $f2 5 | p: .word 0 # double *p 6 | res: .space 48 # array with 6 doubles 7 | c: .byte 'c' # char c = 'c' 8 | # messages 9 | newline: .asciiz "\n" 10 | nbsp: .asciiz " " 11 | iteration3: .asciiz "iteration: 3\n" 12 | 13 | .text 14 | main: 15 | 16 | # val = 2.5 17 | li.d $f2, 2.5 18 | s.d $f2, val 19 | 20 | # p = &res 21 | la $s0, res 22 | sw $s0, p($0) 23 | 24 | # for loop 25 | li $t0, 0 # i = 0 26 | li $t1, 0 # address counter 27 | for: bge $t0, 10, end_for # i < 10 28 | # if(i > 5) break for loop 29 | # break 30 | if1: bgt $t0, 5, end_for 31 | 32 | elseif: bne $t0, 5, else1 33 | # i = 2 * i 34 | mul $t0, $t0, 2 35 | 36 | # val = func1() 37 | jal func1 38 | mtc1.d $v0, $f2 39 | cvt.d.w $f2, $f2 40 | 41 | # *p = add(val, i) 42 | mov.d $f0, $f2 43 | move $a0, $t0 44 | jal add_func 45 | s.d $f12, 0($s0) 46 | 47 | # print(res[i]) 48 | l.d $f12, res($t1) 49 | li $v0, 3 50 | syscall 51 | 52 | # print("\n") 53 | li $v0, 4 54 | la $a0, newline 55 | syscall 56 | 57 | # continue (with next iteration) 58 | j incr_for 59 | 60 | else1: 61 | # *p = add(val, i) 62 | mov.d $f0, $f2 63 | move $a0, $t0 64 | jal add_func 65 | s.d $f12, 0($s0) 66 | 67 | # val = res[i] 68 | l.d $f4, res($t1) 69 | mov.d $f2, $f4 70 | s.d $f2, val 71 | 72 | # print(res[i)) 73 | l.d $f12, res($t1) 74 | li $v0, 3 75 | syscall 76 | 77 | # print("\n") 78 | li $v0, 4 79 | la $a0, newline 80 | syscall 81 | 82 | # p = p + 1 83 | addi $s0, $s0, 8 84 | sw $s0, p($0) 85 | 86 | # if(i == 2 && val == 4.5){ print("iteration: 3\n")} 87 | if2: 88 | # i == 2 89 | bne $t0, 2, incr_for 90 | # val == 4.5 91 | li.d $f6, 4.5 92 | c.eq.d $f2, $f6 93 | # branch if false (and so not equal) 94 | bc1f incr_for 95 | 96 | # print("iteration: 3\n") 97 | li $v0, 4 98 | la $a0, iteration3 99 | syscall 100 | 101 | incr_for: 102 | # i++ 103 | addi $t0, $t0, 1 104 | addi $t1, $t1, 8 105 | j for 106 | end_for: 107 | 108 | # while(i < 12){ ... } 109 | while: bge $t0, 12, end_while 110 | # print(i) 111 | li $v0, 1 112 | move $a0, $t0 113 | syscall 114 | 115 | # print(" ") 116 | li $v0, 4 117 | la $a0, nbsp 118 | syscall 119 | 120 | # func2(c) 121 | lb $a0, c($0) 122 | jal func2 123 | 124 | # i++ 125 | addi $t0, $t0, 1 126 | 127 | end_while: 128 | 129 | # print("\n"); 130 | li $v0, 4 131 | la $a0, newline 132 | syscall 133 | 134 | # terminate program 135 | li $v0, 10 136 | syscall 137 | 138 | func1: 139 | # return 5 140 | li $v0, 5 141 | jr $ra 142 | 143 | func2: 144 | # print(c) 145 | li $v0, 11 146 | # parameter already in $a0 147 | syscall 148 | 149 | jr $ra 150 | 151 | add_func: 152 | # parameter a in $f0 153 | # parameter b in $a0 154 | 155 | # convert int b to double 156 | mtc1.d $a0, $f6 157 | cvt.d.w $f6, $f6 158 | 159 | # res = a + b + (-5) 160 | 161 | # temp = a + b 162 | add.d $f12, $f0, $f6 163 | 164 | # res = temp + (-5) 165 | li.d $f8, -5.0 166 | add.d $f12, $f12, $f8 167 | 168 | # result in $f12 169 | jr $ra 170 | -------------------------------------------------------------------------------- /src/parser.y: -------------------------------------------------------------------------------- 1 | %{ 2 | #include 3 | #include 4 | #include "../include/symtab.h" 5 | 6 | extern int lineno; 7 | extern int yylex(); 8 | void yyerror(char *message); 9 | %} 10 | 11 | /* YYSTYPE union */ 12 | %union{ 13 | char char_val; 14 | int int_val; 15 | double double_val; 16 | char* str_val; 17 | list_t* symtab_item; 18 | } 19 | 20 | /* token definition */ 21 | %token CHAR INT FLOAT DOUBLE IF ELSE WHILE FOR CONTINUE BREAK VOID RETURN 22 | %token ADDOP MULOP DIVOP INCR OROP ANDOP NOTOP EQUOP RELOP 23 | %token LPAREN RPAREN LBRACK RBRACK LBRACE RBRACE SEMI DOT COMMA ASSIGN REFER 24 | %token ID 25 | %token ICONST 26 | %token FCONST 27 | %token CCONST 28 | %token STRING 29 | 30 | /* precedencies and associativities */ 31 | %left LPAREN RPAREN LBRACK RBRACK 32 | %right NOTOP INCR REFER 33 | %left MULOP DIVOP 34 | %left ADDOP 35 | %left RELOP 36 | %left EQUOP 37 | %left OROP 38 | %left ANDOP 39 | %right ASSIGN 40 | %left COMMA 41 | 42 | 43 | %start program 44 | 45 | /* expression rules */ 46 | 47 | %% 48 | 49 | program: declarations statements RETURN SEMI functions_optional ; 50 | 51 | /* declarations */ 52 | declarations: declarations declaration | declaration; 53 | 54 | declaration: type names SEMI ; 55 | 56 | type: INT | CHAR | FLOAT | DOUBLE | VOID ; 57 | 58 | names: names COMMA variable | names COMMA init | variable | init ; 59 | 60 | variable: ID | 61 | pointer ID | 62 | ID array 63 | ; 64 | 65 | pointer: pointer MULOP | MULOP ; 66 | 67 | array: array LBRACK expression RBRACK | LBRACK expression RBRACK ; 68 | 69 | init: var_init | array_init ; 70 | 71 | var_init : ID ASSIGN constant 72 | 73 | array_init: ID array ASSIGN LBRACE values RBRACE ; 74 | 75 | values: values COMMA constant | constant ; 76 | 77 | /* statements */ 78 | statements: statements statement | statement ; 79 | 80 | statement: 81 | if_statement | for_statement | while_statement | assigment SEMI | 82 | CONTINUE SEMI | BREAK SEMI | function_call SEMI | ID INCR SEMI | INCR ID SEMI 83 | ; 84 | 85 | if_statement: 86 | IF LPAREN expression RPAREN tail else_if optional_else | 87 | IF LPAREN expression RPAREN tail optional_else 88 | ; 89 | 90 | else_if: 91 | else_if ELSE IF LPAREN expression RPAREN tail | 92 | ELSE IF LPAREN expression RPAREN tail 93 | ; 94 | 95 | optional_else: ELSE tail | /* empty */ ; 96 | 97 | for_statement: FOR LPAREN assigment SEMI expression SEMI expression RPAREN tail ; 98 | 99 | while_statement: WHILE LPAREN expression RPAREN tail ; 100 | 101 | tail: LBRACE statements RBRACE ; 102 | 103 | expression: 104 | expression ADDOP expression | 105 | expression MULOP expression | 106 | expression DIVOP expression | 107 | ID INCR | 108 | INCR ID | 109 | expression OROP expression | 110 | expression ANDOP expression | 111 | NOTOP expression | 112 | expression EQUOP expression | 113 | expression RELOP expression | 114 | LPAREN expression RPAREN | 115 | var_ref | 116 | sign constant | 117 | function_call 118 | ; 119 | 120 | sign: ADDOP | /* empty */ ; 121 | 122 | constant: ICONST | FCONST | CCONST ; 123 | 124 | assigment: var_ref ASSIGN expression ; 125 | 126 | var_ref : variable | REFER variable ; 127 | 128 | function_call: ID LPAREN call_params RPAREN; 129 | 130 | call_params: call_param | STRING | /* empty */ 131 | 132 | call_param: call_param COMMA expression | expression ; 133 | 134 | /* functions */ 135 | functions_optional: functions | /* empty */ ; 136 | 137 | functions: functions function | function ; 138 | 139 | function: function_head function_tail ; 140 | 141 | function_head: return_type ID LPAREN parameters_optional RPAREN ; 142 | 143 | return_type: type | type pointer ; 144 | 145 | parameters_optional: parameters | /* empty */ ; 146 | 147 | parameters: parameters COMMA parameter | parameter ; 148 | 149 | parameter : type variable ; 150 | 151 | function_tail: LBRACE declarations_optional statements_optional return_optional RBRACE ; 152 | 153 | declarations_optional: declarations | /* empty */ ; 154 | 155 | statements_optional: statements | /* empty */ ; 156 | 157 | return_optional: RETURN expression SEMI | /* empty */ ; 158 | 159 | %% 160 | 161 | void yyerror (char *message) 162 | { 163 | fprintf(stderr, "Syntax error at line %d\n", lineno); 164 | exit(1); 165 | } 166 | 167 | /* 168 | int main (int argc, char *argv[]){ 169 | 170 | // initialize symbol table 171 | init_hash_table(); 172 | 173 | // parsing 174 | int flag; 175 | yyin = fopen(argv[1], "r"); 176 | flag = yyparse(); 177 | fclose(yyin); 178 | 179 | printf("Parsing finished!"); 180 | 181 | // symbol table dump 182 | yyout = fopen("symtab_dump.out", "w"); 183 | symtab_dump(yyout); 184 | fclose(yyout); 185 | 186 | return flag; 187 | } 188 | */ 189 | -------------------------------------------------------------------------------- /src/symtab.c: -------------------------------------------------------------------------------- 1 | #include "../include/symtab.h" 2 | #include 3 | #include 4 | #include 5 | 6 | /* current scope */ 7 | int cur_scope = 0; 8 | 9 | void init_hash_table() { 10 | int i; 11 | hash_table = malloc(SIZE * sizeof(list_t *)); 12 | for (i = 0; i < SIZE; i++) 13 | hash_table[i] = NULL; 14 | } 15 | 16 | unsigned int hash(char *key) { 17 | unsigned int hashval = 0; 18 | for (; *key != '\0'; key++) 19 | hashval += *key; 20 | hashval += key[0] % 11 + (key[0] << 3) - key[0]; 21 | return hashval % SIZE; 22 | } 23 | 24 | void insert(char *name, int len, int type, int lineno) { 25 | unsigned int hashval = hash(name); 26 | list_t *l = hash_table[hashval]; 27 | 28 | while ((l != NULL) && (strcmp(name, l->st_name) != 0)) 29 | l = l->next; 30 | 31 | /* variable not yet in table */ 32 | if (l == NULL) { 33 | l = (list_t *)malloc(sizeof(list_t)); 34 | strncpy(l->st_name, name, len); 35 | /* add to hashtable */ 36 | l->st_type = type; 37 | l->scope = cur_scope; 38 | l->lines = (RefList *)malloc(sizeof(RefList)); 39 | l->lines->lineno = lineno; 40 | l->lines->next = NULL; 41 | l->next = hash_table[hashval]; 42 | hash_table[hashval] = l; 43 | printf("Inserted %s for the first time with linenumber %d!\n", name, 44 | lineno); // error checking 45 | } 46 | /* found in table, so just add line number */ 47 | else { 48 | l->scope = cur_scope; 49 | RefList *t = l->lines; 50 | while (t->next != NULL) 51 | t = t->next; 52 | /* add linenumber to reference list */ 53 | t->next = (RefList *)malloc(sizeof(RefList)); 54 | t->next->lineno = lineno; 55 | t->next->next = NULL; 56 | printf("Found %s again at line %d!\n", name, lineno); 57 | } 58 | } 59 | 60 | list_t *lookup(char *name) { /* return symbol if found or NULL if not found */ 61 | unsigned int hashval = hash(name); 62 | list_t *l = hash_table[hashval]; 63 | while ((l != NULL) && (strcmp(name, l->st_name) != 0)) 64 | l = l->next; 65 | return l; // NULL is not found 66 | } 67 | 68 | list_t * 69 | lookup_scope(char *name, 70 | int scope) { /* return symbol if found or NULL if not found */ 71 | unsigned int hashval = hash(name); 72 | list_t *l = hash_table[hashval]; 73 | while ((l != NULL) && (strcmp(name, l->st_name) != 0) && 74 | (scope != l->scope)) 75 | l = l->next; 76 | return l; // NULL is not found 77 | } 78 | 79 | void hide_scope() { /* hide the current scope */ 80 | if (cur_scope > 0) 81 | cur_scope--; 82 | } 83 | 84 | void incr_scope() { /* go to next scope */ cur_scope++; } 85 | 86 | /* print to stdout by default */ 87 | void symtab_dump(FILE *of) { 88 | int i; 89 | fprintf(of, "------------ ------ ------------\n"); 90 | fprintf(of, "Name Type Line Numbers\n"); 91 | fprintf(of, "------------ ------ -------------\n"); 92 | for (i = 0; i < SIZE; ++i) { 93 | if (hash_table[i] != NULL) { 94 | list_t *l = hash_table[i]; 95 | while (l != NULL) { 96 | RefList *t = l->lines; 97 | fprintf(of, "%-12s ", l->st_name); 98 | if (l->st_type == INT_TYPE) 99 | fprintf(of, "%-7s", "int"); 100 | else if (l->st_type == REAL_TYPE) 101 | fprintf(of, "%-7s", "real"); 102 | else if (l->st_type == STR_TYPE) 103 | fprintf(of, "%-7s", "string"); 104 | else if (l->st_type == ARRAY_TYPE) { 105 | fprintf(of, "array of "); 106 | if (l->inf_type == INT_TYPE) 107 | fprintf(of, "%-7s", "int"); 108 | else if (l->inf_type == REAL_TYPE) 109 | fprintf(of, "%-7s", "real"); 110 | else if (l->inf_type == STR_TYPE) 111 | fprintf(of, "%-7s", "string"); 112 | else 113 | fprintf(of, "%-7s", "undef"); 114 | } else if (l->st_type == FUNCTION_TYPE) { 115 | fprintf(of, "%-7s %s", "function returns "); 116 | if (l->inf_type == INT_TYPE) 117 | fprintf(of, "%-7s", "int"); 118 | else if (l->inf_type == REAL_TYPE) 119 | fprintf(of, "%-7s", "real"); 120 | else if (l->inf_type == STR_TYPE) 121 | fprintf(of, "%-7s", "string"); 122 | else 123 | fprintf(of, "%-7s", "undef"); 124 | } else 125 | fprintf(of, "%-7s", "undef"); // if UNDEF or 0 126 | while (t != NULL) { 127 | fprintf(of, "%4d ", t->lineno); 128 | t = t->next; 129 | } 130 | fprintf(of, "\n"); 131 | l = l->next; 132 | } 133 | } 134 | } 135 | } 136 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # compiler 2 | 3 | ![Compiler Design Steps](/assets/steps_dark.jpg#gh-dark-mode-only) 4 | ![Compiler Design Steps](/assets/steps_light.jpg#gh-light-mode-only) 5 | 6 | This repository contains the code for a compiler implementation for a simple, C-like language that relies on the C tools Flex and Bison. 7 | 8 | A comprehensive tutorial series is also available. 9 | 10 | The project was unfortunately abandoned for over five years due to the maintainer's time constraints. 11 | 12 | Due to the 2020 Steemit dispute, when the project was revitalized the tutorial series resumed on Hive instead. 13 | 14 | > [!IMPORTANT] 15 | > A major overhaul of the repository is currently underway (see open issue #5). Although the project had reached the code generation stage, improvements to the code base have necessitated a temporary return to the post-syntax analysis stage. 16 | 17 | # Prerequisites 18 | 19 | - GCC (GNU Compiler Collection) 20 | - Make 21 | - Flex (derivative of Lex) 22 | - Bison (derivative of Yacc) 23 | - QtSpim (MIPS32 Simulator) 24 | 25 | 26 | # Basic Installation 27 | 28 | ## Linux 29 | 30 | For Arch-based distributions: 31 | ``` 32 | sudo pacman -Syu 33 | sudo pacman -S --needed base-devel 34 | ``` 35 | 36 | > [!NOTE] 37 | > `base-devel` includes `gcc`, `make`, `flex`, `bison`, and other core development tools. Alternatively, you can install each separately. 38 | 39 | 40 | For Debian-based distributions 41 | ``` 42 | sudo apt update 43 | sudo apt install build-essential flex bison 44 | ``` 45 | 46 | > [!NOTE] 47 | > `build-essential` includes `gcc`, `make`, and other core build tools. Alternatively, you can install each separately. 48 | 49 | For Fedora-based distributions 50 | ``` 51 | sudo dnf makecache 52 | sudo dnf group install development-tools 53 | sudo dnf install flex flex-devel bison bison-devel 54 | ``` 55 | 56 | > [!NOTE] 57 | > `development-tools` group includes `gcc`, `make`, and other core build tools. Alternatively, you can install each separately. 58 | 59 | 60 | ## Microsoft Windows 61 | 62 | It is highly recommended that you use a Linux distribution instead, through any method you prefer. 63 | 64 | Options include: 65 | 66 | - Windows Subsystem for Linux (WSL), preferably version 2 67 | - Docker or Podman containers 68 | - Virtual Machines 69 | 70 | ## macOS 71 | 72 | I am not very familiar with Macintosh systems. 73 | However, it seems that you first need to install Apple's command-line developer tools, which will provide you with `make`, `clang` and `gcc` (via clang), as well as other development tools. 74 | Next, install a package manager such as Homebrew (`brew`), through which you can then install `flex` and `bison`. 75 | 76 | ``` 77 | xcode-select --install 78 | /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)" 79 | brew install flex bison 80 | ``` 81 | 82 | ## MIPS32 Emulation (QtSpim) 83 | 84 | Regarding MIPS32 simulation, note that there is a Flatpak package for *QtSpim* that appears to work just fine on Arch Linux. 85 | 86 | If you are on Microsoft Windows, macOS, or a Debian-based Linux distribution, you should be good to go with one of the [recent releases of QtSpim on SourceForge](https://sourceforge.net/projects/spimsimulator/files/). 87 | 88 | 89 | # Getting Started 90 | 91 | ## Building the compiler from source 92 | 93 | Clone the repository and change into the directory: 94 | 95 | ``` 96 | git clone https://github.com/drifter1/compiler.git 97 | cd compiler 98 | ``` 99 | 100 | To build the compiler simply type `make` in this directory. 101 | 102 | By default, the executable will be located in the subdirectory *bin* and called *compiler*. 103 | 104 | ## Running the included examples 105 | 106 | Examples are included in the *examples* subdirectory. You can compile *example1.c* in the Simple-C language via: 107 | 108 | ``` 109 | ./bin/compiler examples/simple_c_examples/example1.c 110 | ``` 111 | 112 | This will print out parsing debugging information in the terminal console and also create a *symtab_dump_out* file. 113 | 114 | **terminal output:** 115 | ``` 116 | Inserted i for the first time with linenumber 1! 117 | Inserted val for the first time with linenumber 2! 118 | Found i again at line 3! 119 | Found i again at line 3! 120 | Found i again at line 3! 121 | Found val again at line 4! 122 | Found val again at line 4! 123 | Found i again at line 4! 124 | Found i again at line 4! 125 | Inserted print for the first time with linenumber 6! 126 | Found val again at line 6! 127 | ``` 128 | 129 | **symtab_dump.out** 130 | ``` 131 | ------------ ------ ------------ 132 | Name Type Line Numbers 133 | ------------ ------ ------------- 134 | i undef 1 3 3 3 4 4 135 | val undef 2 4 4 6 136 | print undef 6 137 | ``` 138 | 139 | ## Cleaning up the build files and binaries 140 | 141 | To clean the build files and binary executable, you just have to type `make clean`. 142 | 143 | > [!NOTE] 144 | > The above command does not remove debugging files such as *symtab_dump_out*, which are created when you use the compiler itself. These files need to be removed manually. 145 | 146 | 147 | # Articles 148 | 149 | The complete list of articles can be found [here](/docs/articles.md). 150 | 151 | 152 | # Next Up 153 | 154 | - Machine Code generation in MIPS Assembly (remaining cases) 155 | - Optimizations in the compiler's source code 156 | -------------------------------------------------------------------------------- /docs/articles.md: -------------------------------------------------------------------------------- 1 | # Articles 2 | 3 | ## General Knowledge and Lexical Analysis 4 | - **Compiler design in general (introduction)** -> https://peakd.com/programming/@drifter1/writing-a-simple-compiler-on-my-own-introduction 5 | - **The simple C-like Language** -> https://peakd.com/programming/@drifter1/writing-a-simple-compiler-on-my-own-a-simple-c-language 6 | - **Lexical Analysis and the implementation of a simple Lexer using Flex** -> https://peakd.com/programming/@drifter1/writing-a-simple-compiler-on-my-own-lexical-analysis-using-flex 7 | - **The basic implementation/structure of a Symbol Table** -> https://peakd.com/programming/@drifter1/writing-a-simple-compiler-on-my-own-symbol-table-basic-structure 8 | - **Using the Symbol Table in the Lexer** -> https://peakd.com/programming/@drifter1/writing-a-simple-compiler-on-my-own-using-symbol-tables-in-the-lexer 9 | 10 | ## Syntax Analysis 11 | - **Syntax Analysis Theory needed**-> https://peakd.com/programming/@drifter1/writing-a-simple-compiler-on-my-own-syntax-analysis-theory 12 | - **Bison tool basics / tutorial** -> https://peakd.com/programming/@drifter1/writing-a-simple-compiler-on-my-own-bison-basics 13 | - **Creating a Grammar for the Language by also implementing a first Parser** -> https://peakd.com/programming/@drifter1/writing-a-simple-compiler-on-my-own-creating-a-grammar-for-our-language 14 | - **Combining Flex and Bison** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-combine-flex-and-bison 15 | - **Passing information from the Lexer to the Parser** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-passing-information-from-lexer-to-parser 16 | - **Finishing Off the Grammar/Parser (part 1)** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-finishing-off-the-grammer-parser-part-1 17 | - **Finishing Off the Grammar/Parser (part 2)** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-finishing-off-the-grammar-parser-part-2-c-flex-bison 18 | 19 | ## Semantic Analysis (1) 20 | - **Semantic Analysis Theory** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-semantic-analysis-theory-c-flex-bison 21 | - **Semantics Examples** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-semantics-examples-c-flex-bison 22 | - **Scope Resolution using Symbol Table** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own---scope-resolution-using-the-symbol-table-cflexbison 23 | - **Type Declaration and Checking** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-type-declaration-and-checking-c-flex-bison 24 | - **Function Semantics (part 1)** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-function-semantics-part-1-c-flex-bison 25 | - **Function Semantics (part 2)** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-function-semantics-part-2-c-flex-bison 26 | 27 | ## Intermediate Code Generation (AST) 28 | - **Abstract Syntax Tree Principle** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-abstract-syntax-tree-principle-c-flex-bison 29 | - **Abstract Syntax Tree Structure** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-abstract-syntax-tree-structure-c-flex-bison 30 | - **Abstract Syntax Tree Management** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-abstract-syntax-tree-management-c-flex-bison 31 | - **Action Rules for Declarations and Initializations** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-action-rules-for-declarations-and-initializations-c-flex-bison 32 | - **Action Rules for Expressions** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-action-rules-for-expressions-c-flex-bison 33 | - **Action Rules for Assignments and Simple Statements** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-action-rules-for-assignments-and-simple-statements-c-flex-bison 34 | - **Action Rules for If-Else Statements** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-action-rules-for-if-else-statements-c-flex-bison 35 | - **Action Rules for Loop Statements and some Fixes** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-action-rules-for-loop-statements-and-some-fixes-c-flex-bison 36 | - **Action Rules for Function Declarations (part 1)** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-action-rules-for-function-declarations-part-1-c-flex-bison 37 | - **Action Rules for Function Declarations (part 2)** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-action-rules-for-function-declarations-part-2-c-flex-bison 38 | - **Action Rules for Function Calls** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-action-rules-for-function-calls-c-flex-bison 39 | 40 | ## Semantic Analysis (2) 41 | - **Datatype attribute for Expressions** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-datatype-attribute-for-expressions-c-flex-bison 42 | - **Type Checking for Assignments** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-type-checking-for-assignments-c-flex-bison 43 | - **Revisit Queue and Parameter Checking (part 1)** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-revisit-queue-and-parameter-checking-part-1-c-flex-bison 44 | - **Revisit Queue and Parameter Checking (part 2)** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-revisit-queue-and-parameter-checking-part-2-c-flex-bison 45 | - **Revisit Queue and Parameter Checking (part 3)** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-revisit-queue-and-parameter-checking-part-3-c-flex-bison 46 | - **Revisit Queue and Parameter Checking (part 4)** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-revisit-queue-and-parameter-checking-part-4-c-flex-bison 47 | - **Revisit Queue and Assignment Checking (part 1)** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-revisit-queue-and-assignment-checking-part-1-c-flex-bison 48 | - **Revisit Queue and Assignment Checking (part 2)** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-revisit-queue-and-assignment-checking-part-2-c-flex-bison 49 | - **Revisit Queue and Assignment Checking (part 3)** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-revisit-queue-and-assignment-checking-part-3-c-flex-bison 50 | 51 | ## Machine Code Generation 52 | - **Machine Code Generation Principles** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-machine-code-generation-principles 53 | - **MIPS Instruction Set** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-mips-instruction-set 54 | - **Simple Examples in MIPS Assembly** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-simple-examples-in-mips-assembly 55 | - **full_example.c in MIPS Assembly (part 1)** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-fullexample-c-in-mips-assembly 56 | - **full_example.c in MIPS Assembly (part 2)** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-fullexample-c-in-mips-assembly-part-2 57 | - **Generating Code for Declarations and Initializations** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-generating-code-for-declarations-and-initializations 58 | - **Generating Code for Array Initializations and String Messages** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-generating-code-for-array-initializations-and-string-messages 59 | - **Register Allocation & Assignment Theory** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-register-allocation-and-assignment-theory 60 | - **Implementing Register Allocation (part 1)** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-implementing-register-allocation-part-1 61 | - **Implementing Register Allocation (part 2)** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-implementing-register-allocation-part-2 62 | - **Implementing Register Allocation (part 3)** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-implementing-register-allocation-part-3 63 | - **Implementing Register Allocation (part 4)** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-implementing-register-allocation-part-4 64 | - **Generating Code for Expressions (part 1)** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-generating-code-for-expressions-part-1 65 | - **Generating Code for Expressions (part 2)** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-generating-code-for-expressions-part-2 66 | - **Generating Code for Expressions (part 3)** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-generating-code-for-expressions-part-3 67 | - **Generating Code for Simple Statements** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-generating-code-for-simple-statements 68 | - **Generating Code for Assignments (part 1)** -> https://peakd.com/utopian-io/@drifter1/writing-a-simple-compiler-on-my-own-generating-code-for-assignments-part-1 69 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | GNU GENERAL PUBLIC LICENSE 2 | Version 3, 29 June 2007 3 | 4 | Copyright (C) 2007 Free Software Foundation, Inc. 5 | Everyone is permitted to copy and distribute verbatim copies 6 | of this license document, but changing it is not allowed. 7 | 8 | Preamble 9 | 10 | The GNU General Public License is a free, copyleft license for 11 | software and other kinds of works. 12 | 13 | The licenses for most software and other practical works are designed 14 | to take away your freedom to share and change the works. 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No Surrender of Others' Freedom. 541 | 542 | If conditions are imposed on you (whether by court order, agreement or 543 | otherwise) that contradict the conditions of this License, they do not 544 | excuse you from the conditions of this License. If you cannot convey a 545 | covered work so as to satisfy simultaneously your obligations under this 546 | License and any other pertinent obligations, then as a consequence you may 547 | not convey it at all. For example, if you agree to terms that obligate you 548 | to collect a royalty for further conveying from those to whom you convey 549 | the Program, the only way you could satisfy both those terms and this 550 | License would be to refrain entirely from conveying the Program. 551 | 552 | 13. Use with the GNU Affero General Public License. 553 | 554 | Notwithstanding any other provision of this License, you have 555 | permission to link or combine any covered work with a work licensed 556 | under version 3 of the GNU Affero General Public License into a single 557 | combined work, and to convey the resulting work. The terms of this 558 | License will continue to apply to the part which is the covered work, 559 | but the special requirements of the GNU Affero General Public License, 560 | section 13, concerning interaction through a network will apply to the 561 | combination as such. 562 | 563 | 14. Revised Versions of this License. 564 | 565 | The Free Software Foundation may publish revised and/or new versions of 566 | the GNU General Public License from time to time. Such new versions will 567 | be similar in spirit to the present version, but may differ in detail to 568 | address new problems or concerns. 569 | 570 | Each version is given a distinguishing version number. If the 571 | Program specifies that a certain numbered version of the GNU General 572 | Public License "or any later version" applies to it, you have the 573 | option of following the terms and conditions either of that numbered 574 | version or of any later version published by the Free Software 575 | Foundation. If the Program does not specify a version number of the 576 | GNU General Public License, you may choose any version ever published 577 | by the Free Software Foundation. 578 | 579 | If the Program specifies that a proxy can decide which future 580 | versions of the GNU General Public License can be used, that proxy's 581 | public statement of acceptance of a version permanently authorizes you 582 | to choose that version for the Program. 583 | 584 | Later license versions may give you additional or different 585 | permissions. However, no additional obligations are imposed on any 586 | author or copyright holder as a result of your choosing to follow a 587 | later version. 588 | 589 | 15. Disclaimer of Warranty. 590 | 591 | THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY 592 | APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT 593 | HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY 594 | OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, 595 | THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 596 | PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM 597 | IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF 598 | ALL NECESSARY SERVICING, REPAIR OR CORRECTION. 599 | 600 | 16. Limitation of Liability. 601 | 602 | IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING 603 | WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS 604 | THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY 605 | GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE 606 | USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF 607 | DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD 608 | PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), 609 | EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF 610 | SUCH DAMAGES. 611 | 612 | 17. Interpretation of Sections 15 and 16. 613 | 614 | If the disclaimer of warranty and limitation of liability provided 615 | above cannot be given local legal effect according to their terms, 616 | reviewing courts shall apply local law that most closely approximates 617 | an absolute waiver of all civil liability in connection with the 618 | Program, unless a warranty or assumption of liability accompanies a 619 | copy of the Program in return for a fee. 620 | 621 | END OF TERMS AND CONDITIONS 622 | 623 | How to Apply These Terms to Your New Programs 624 | 625 | If you develop a new program, and you want it to be of the greatest 626 | possible use to the public, the best way to achieve this is to make it 627 | free software which everyone can redistribute and change under these terms. 628 | 629 | To do so, attach the following notices to the program. It is safest 630 | to attach them to the start of each source file to most effectively 631 | state the exclusion of warranty; and each file should have at least 632 | the "copyright" line and a pointer to where the full notice is found. 633 | 634 | 635 | Copyright (C) 636 | 637 | This program is free software: you can redistribute it and/or modify 638 | it under the terms of the GNU General Public License as published by 639 | the Free Software Foundation, either version 3 of the License, or 640 | (at your option) any later version. 641 | 642 | This program is distributed in the hope that it will be useful, 643 | but WITHOUT ANY WARRANTY; without even the implied warranty of 644 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 645 | GNU General Public License for more details. 646 | 647 | You should have received a copy of the GNU General Public License 648 | along with this program. If not, see . 649 | 650 | Also add information on how to contact you by electronic and paper mail. 651 | 652 | If the program does terminal interaction, make it output a short 653 | notice like this when it starts in an interactive mode: 654 | 655 | Copyright (C) 656 | This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'. 657 | This is free software, and you are welcome to redistribute it 658 | under certain conditions; type `show c' for details. 659 | 660 | The hypothetical commands `show w' and `show c' should show the appropriate 661 | parts of the General Public License. Of course, your program's commands 662 | might be different; for a GUI interface, you would use an "about box". 663 | 664 | You should also get your employer (if you work as a programmer) or school, 665 | if any, to sign a "copyright disclaimer" for the program, if necessary. 666 | For more information on this, and how to apply and follow the GNU GPL, see 667 | . 668 | 669 | The GNU General Public License does not permit incorporating your program 670 | into proprietary programs. If your program is a subroutine library, you 671 | may consider it more useful to permit linking proprietary applications with 672 | the library. If this is what you want to do, use the GNU Lesser General 673 | Public License instead of this License. But first, please read 674 | . 675 | --------------------------------------------------------------------------------