C99 Lex/Flex & YACC/Bison Grammars

c99.l

D			[0-9]
L			[a-zA-Z_]
H			[a-fA-F0-9]
E			([Ee][+-]?{D}+)
P                       ([Pp][+-]?{D}+)
FS			(f|F|l|L)
IS                      ((u|U)|(u|U)?(l|L|ll|LL)|(l|L|ll|LL)(u|U))

%{
#include <stdio.h>
#include "y.tab.h"

void count(void);
%}

%%
"/*"			{ comment(); }
"//"[^\n]*              { /* consume //-comment */ }


"auto"			{ count(); return(AUTO); }
"_Bool"			{ count(); return(BOOL); }
"break"			{ count(); return(BREAK); }
"case"			{ count(); return(CASE); }
"char"			{ count(); return(CHAR); }
"_Complex"		{ count(); return(COMPLEX); }
"const"			{ count(); return(CONST); }
"continue"		{ count(); return(CONTINUE); }
"default"		{ count(); return(DEFAULT); }
"do"			{ count(); return(DO); }
"double"		{ count(); return(DOUBLE); }
"else"			{ count(); return(ELSE); }
"enum"			{ count(); return(ENUM); }
"extern"		{ count(); return(EXTERN); }
"float"			{ count(); return(FLOAT); }
"for"			{ count(); return(FOR); }
"goto"			{ count(); return(GOTO); }
"if"			{ count(); return(IF); }
"_Imaginary"		{ count(); return(IMAGINARY); }
"inline"		{ count(); return(INLINE); }
"int"			{ count(); return(INT); }
"long"			{ count(); return(LONG); }
"register"		{ count(); return(REGISTER); }
"restrict"		{ count(); return(RESTRICT); }
"return"		{ count(); return(RETURN); }
"short"			{ count(); return(SHORT); }
"signed"		{ count(); return(SIGNED); }
"sizeof"		{ count(); return(SIZEOF); }
"static"		{ count(); return(STATIC); }
"struct"		{ count(); return(STRUCT); }
"switch"		{ count(); return(SWITCH); }
"typedef"		{ count(); return(TYPEDEF); }
"union"			{ count(); return(UNION); }
"unsigned"		{ count(); return(UNSIGNED); }
"void"			{ count(); return(VOID); }
"volatile"		{ count(); return(VOLATILE); }
"while"			{ count(); return(WHILE); }

{L}({L}|{D})*		{ count(); return(check_type()); }

0[xX]{H}+{IS}?		{ count(); return(CONSTANT); }
0[0-7]*{IS}?		{ count(); return(CONSTANT); }
[1-9]{D}*{IS}?		{ count(); return(CONSTANT); }
L?'(\\.|[^\\'\n])+'	{ count(); return(CONSTANT); }

{D}+{E}{FS}?		{ count(); return(CONSTANT); }
{D}*"."{D}+{E}?{FS}?	{ count(); return(CONSTANT); }
{D}+"."{D}*{E}?{FS}?	{ count(); return(CONSTANT); }
0[xX]{H}+{P}{FS}?	{ count(); return(CONSTANT); }
0[xX]{H}*"."{H}+{P}?{FS}?     { count(); return(CONSTANT); }
0[xX]{H}+"."{H}*{P}?{FS}?     { count(); return(CONSTANT); }


L?\"(\\.|[^\\"\n])*\"	{ count(); return(STRING_LITERAL); }

"..."			{ count(); return(ELLIPSIS); }
">>="			{ count(); return(RIGHT_ASSIGN); }
"<<="			{ count(); return(LEFT_ASSIGN); }
"+="			{ count(); return(ADD_ASSIGN); }
"-="			{ count(); return(SUB_ASSIGN); }
"*="			{ count(); return(MUL_ASSIGN); }
"/="			{ count(); return(DIV_ASSIGN); }
"%="			{ count(); return(MOD_ASSIGN); }
"&="			{ count(); return(AND_ASSIGN); }
"^="			{ count(); return(XOR_ASSIGN); }
"|="			{ count(); return(OR_ASSIGN); }
">>"			{ count(); return(RIGHT_OP); }
"<<"			{ count(); return(LEFT_OP); }
"++"			{ count(); return(INC_OP); }
"--"			{ count(); return(DEC_OP); }
"->"			{ count(); return(PTR_OP); }
"&&"			{ count(); return(AND_OP); }
"||"			{ count(); return(OR_OP); }
"<="			{ count(); return(LE_OP); }
">="			{ count(); return(GE_OP); }
"=="			{ count(); return(EQ_OP); }
"!="			{ count(); return(NE_OP); }
";"			{ count(); return(';'); }
("{"|"<%")		{ count(); return('{'); }
("}"|"%>")		{ count(); return('}'); }
","			{ count(); return(','); }
":"			{ count(); return(':'); }
"="			{ count(); return('='); }
"("			{ count(); return('('); }
")"			{ count(); return(')'); }
("["|"<:")		{ count(); return('['); }
("]"|":>")		{ count(); return(']'); }
"."			{ count(); return('.'); }
"&"			{ count(); return('&'); }
"!"			{ count(); return('!'); }
"~"			{ count(); return('~'); }
"-"			{ count(); return('-'); }
"+"			{ count(); return('+'); }
"*"			{ count(); return('*'); }
"/"			{ count(); return('/'); }
"%"			{ count(); return('%'); }
"<"			{ count(); return('<'); }
">"			{ count(); return('>'); }
"^"			{ count(); return('^'); }
"|"			{ count(); return('|'); }
"?"			{ count(); return('?'); }

[ \t\v\n\f]		{ count(); }
.			{ /* Add code to complain about unmatched characters */ }

%%

int yywrap(void)
{
	return 1;
}


void comment(void)
{
	char c, prev = 0;
  
	while ((c = input()) != 0)      /* (EOF maps to 0) */
	{
		if (c == '/' && prev == '*')
			return;
		prev = c;
	}
	error("unterminated comment");
}


int column = 0;

void count(void)
{
	int i;

	for (i = 0; yytext[i] != '\0'; i++)
		if (yytext[i] == '\n')
			column = 0;
		else if (yytext[i] == '\t')
			column += 8 - (column % 8);
		else
			column++;

	ECHO;
}


int check_type(void)
{
/*
* pseudo code --- this is what it should check
*
*	if (yytext == type_name)
*		return TYPE_NAME;
*
*	return IDENTIFIER;
*/

/*
*	it actually will only return IDENTIFIER
*/

	return IDENTIFIER;
}

c99.y

%token IDENTIFIER CONSTANT STRING_LITERAL SIZEOF
%token PTR_OP INC_OP DEC_OP LEFT_OP RIGHT_OP LE_OP GE_OP EQ_OP NE_OP
%token AND_OP OR_OP MUL_ASSIGN DIV_ASSIGN MOD_ASSIGN ADD_ASSIGN
%token SUB_ASSIGN LEFT_ASSIGN RIGHT_ASSIGN AND_ASSIGN
%token XOR_ASSIGN OR_ASSIGN TYPE_NAME

%token TYPEDEF EXTERN STATIC AUTO REGISTER INLINE RESTRICT
%token CHAR SHORT INT LONG SIGNED UNSIGNED FLOAT DOUBLE CONST VOLATILE VOID
%token BOOL COMPLEX IMAGINARY
%token STRUCT UNION ENUM ELLIPSIS

%token CASE DEFAULT IF ELSE SWITCH WHILE DO FOR GOTO CONTINUE BREAK RETURN

%start translation_unit
%%

primary_expression
	: IDENTIFIER
	| CONSTANT
	| STRING_LITERAL
	| '(' expression ')'
	;

postfix_expression
	: primary_expression
	| postfix_expression '[' expression ']'
	| postfix_expression '(' ')'
	| postfix_expression '(' argument_expression_list ')'
	| postfix_expression '.' IDENTIFIER
	| postfix_expression PTR_OP IDENTIFIER
	| postfix_expression INC_OP
	| postfix_expression DEC_OP
	| '(' type_name ')' '{' initializer_list '}'
	| '(' type_name ')' '{' initializer_list ',' '}'
	;

argument_expression_list
	: assignment_expression
	| argument_expression_list ',' assignment_expression
	;

unary_expression
	: postfix_expression
	| INC_OP unary_expression
	| DEC_OP unary_expression
	| unary_operator cast_expression
	| SIZEOF unary_expression
	| SIZEOF '(' type_name ')'
	;

unary_operator
	: '&'
	| '*'
	| '+'
	| '-'
	| '~'
	| '!'
	;

cast_expression
	: unary_expression
	| '(' type_name ')' cast_expression
	;

multiplicative_expression
	: cast_expression
	| multiplicative_expression '*' cast_expression
	| multiplicative_expression '/' cast_expression
	| multiplicative_expression '%' cast_expression
	;

additive_expression
	: multiplicative_expression
	| additive_expression '+' multiplicative_expression
	| additive_expression '-' multiplicative_expression
	;

shift_expression
	: additive_expression
	| shift_expression LEFT_OP additive_expression
	| shift_expression RIGHT_OP additive_expression
	;

relational_expression
	: shift_expression
	| relational_expression '<' shift_expression
	| relational_expression '>' shift_expression
	| relational_expression LE_OP shift_expression
	| relational_expression GE_OP shift_expression
	;

equality_expression
	: relational_expression
	| equality_expression EQ_OP relational_expression
	| equality_expression NE_OP relational_expression
	;

and_expression
	: equality_expression
	| and_expression '&' equality_expression
	;

exclusive_or_expression
	: and_expression
	| exclusive_or_expression '^' and_expression
	;

inclusive_or_expression
	: exclusive_or_expression
	| inclusive_or_expression '|' exclusive_or_expression
	;

logical_and_expression
	: inclusive_or_expression
	| logical_and_expression AND_OP inclusive_or_expression
	;

logical_or_expression
	: logical_and_expression
	| logical_or_expression OR_OP logical_and_expression
	;

conditional_expression
	: logical_or_expression
	| logical_or_expression '?' expression ':' conditional_expression
	;

assignment_expression
	: conditional_expression
	| unary_expression assignment_operator assignment_expression
	;

assignment_operator
	: '='
	| MUL_ASSIGN
	| DIV_ASSIGN
	| MOD_ASSIGN
	| ADD_ASSIGN
	| SUB_ASSIGN
	| LEFT_ASSIGN
	| RIGHT_ASSIGN
	| AND_ASSIGN
	| XOR_ASSIGN
	| OR_ASSIGN
	;

expression
	: assignment_expression
	| expression ',' assignment_expression
	;

constant_expression
	: conditional_expression
	;

declaration
	: declaration_specifiers ';'
	| declaration_specifiers init_declarator_list ';'
	;

declaration_specifiers
	: storage_class_specifier
	| storage_class_specifier declaration_specifiers
	| type_specifier
	| type_specifier declaration_specifiers
	| type_qualifier
	| type_qualifier declaration_specifiers
	| function_specifier
	| function_specifier declaration_specifiers
	;

init_declarator_list
	: init_declarator
	| init_declarator_list ',' init_declarator
	;

init_declarator
	: declarator
	| declarator '=' initializer
	;

storage_class_specifier
	: TYPEDEF
	| EXTERN
	| STATIC
	| AUTO
	| REGISTER
	;

type_specifier
	: VOID
	| CHAR
	| SHORT
	| INT
	| LONG
	| FLOAT
	| DOUBLE
	| SIGNED
	| UNSIGNED
	| BOOL
	| COMPLEX
	| IMAGINARY
	| struct_or_union_specifier
	| enum_specifier
	| TYPE_NAME
	;

struct_or_union_specifier
	: struct_or_union IDENTIFIER '{' struct_declaration_list '}'
	| struct_or_union '{' struct_declaration_list '}'
	| struct_or_union IDENTIFIER
	;

struct_or_union
	: STRUCT
	| UNION
	;

struct_declaration_list
	: struct_declaration
	| struct_declaration_list struct_declaration
	;

struct_declaration
	: specifier_qualifier_list struct_declarator_list ';'
	;

specifier_qualifier_list
	: type_specifier specifier_qualifier_list
	| type_specifier
	| type_qualifier specifier_qualifier_list
	| type_qualifier
	;

struct_declarator_list
	: struct_declarator
	| struct_declarator_list ',' struct_declarator
	;

struct_declarator
	: declarator
	| ':' constant_expression
	| declarator ':' constant_expression
	;

enum_specifier
	: ENUM '{' enumerator_list '}'
	| ENUM IDENTIFIER '{' enumerator_list '}'
	| ENUM '{' enumerator_list ',' '}'
	| ENUM IDENTIFIER '{' enumerator_list ',' '}'
	| ENUM IDENTIFIER
	;

enumerator_list
	: enumerator
	| enumerator_list ',' enumerator
	;

enumerator
	: IDENTIFIER
	| IDENTIFIER '=' constant_expression
	;

type_qualifier
	: CONST
	| RESTRICT
	| VOLATILE
	;

function_specifier
	: INLINE
	;

declarator
	: pointer direct_declarator
	| direct_declarator
	;


direct_declarator
	: IDENTIFIER
	| '(' declarator ')'
	| direct_declarator '[' type_qualifier_list assignment_expression ']'
	| direct_declarator '[' type_qualifier_list ']'
	| direct_declarator '[' assignment_expression ']'
	| direct_declarator '[' STATIC type_qualifier_list assignment_expression ']'
	| direct_declarator '[' type_qualifier_list STATIC assignment_expression ']'
	| direct_declarator '[' type_qualifier_list '*' ']'
	| direct_declarator '[' '*' ']'
	| direct_declarator '[' ']'
	| direct_declarator '(' parameter_type_list ')'
	| direct_declarator '(' identifier_list ')'
	| direct_declarator '(' ')'
	;

pointer
	: '*'
	| '*' type_qualifier_list
	| '*' pointer
	| '*' type_qualifier_list pointer
	;

type_qualifier_list
	: type_qualifier
	| type_qualifier_list type_qualifier
	;


parameter_type_list
	: parameter_list
	| parameter_list ',' ELLIPSIS
	;

parameter_list
	: parameter_declaration
	| parameter_list ',' parameter_declaration
	;

parameter_declaration
	: declaration_specifiers declarator
	| declaration_specifiers abstract_declarator
	| declaration_specifiers
	;

identifier_list
	: IDENTIFIER
	| identifier_list ',' IDENTIFIER
	;

type_name
	: specifier_qualifier_list
	| specifier_qualifier_list abstract_declarator
	;

abstract_declarator
	: pointer
	| direct_abstract_declarator
	| pointer direct_abstract_declarator
	;

direct_abstract_declarator
	: '(' abstract_declarator ')'
	| '[' ']'
	| '[' assignment_expression ']'
	| direct_abstract_declarator '[' ']'
	| direct_abstract_declarator '[' assignment_expression ']'
	| '[' '*' ']'
	| direct_abstract_declarator '[' '*' ']'
	| '(' ')'
	| '(' parameter_type_list ')'
	| direct_abstract_declarator '(' ')'
	| direct_abstract_declarator '(' parameter_type_list ')'
	;

initializer
	: assignment_expression
	| '{' initializer_list '}'
	| '{' initializer_list ',' '}'
	;

initializer_list
	: initializer
	| designation initializer
	| initializer_list ',' initializer
	| initializer_list ',' designation initializer
	;

designation
	: designator_list '='
	;

designator_list
	: designator
	| designator_list designator
	;

designator
	: '[' constant_expression ']'
	| '.' IDENTIFIER
	;

statement
	: labeled_statement
	| compound_statement
	| expression_statement
	| selection_statement
	| iteration_statement
	| jump_statement
	;

labeled_statement
	: IDENTIFIER ':' statement
	| CASE constant_expression ':' statement
	| DEFAULT ':' statement
	;

compound_statement
	: '{' '}'
	| '{' block_item_list '}'
	;

block_item_list
	: block_item
	| block_item_list block_item
	;

block_item
	: declaration
	| statement
	;

expression_statement
	: ';'
	| expression ';'
	;

selection_statement
	: IF '(' expression ')' statement
	| IF '(' expression ')' statement ELSE statement
	| SWITCH '(' expression ')' statement
	;

iteration_statement
	: WHILE '(' expression ')' statement
	| DO statement WHILE '(' expression ')' ';'
	| FOR '(' expression_statement expression_statement ')' statement
	| FOR '(' expression_statement expression_statement expression ')' statement
	| FOR '(' declaration expression_statement ')' statement
	| FOR '(' declaration expression_statement expression ')' statement
	;

jump_statement
	: GOTO IDENTIFIER ';'
	| CONTINUE ';'
	| BREAK ';'
	| RETURN ';'
	| RETURN expression ';'
	;

translation_unit
	: external_declaration
	| translation_unit external_declaration
	;

external_declaration
	: function_definition
	| declaration
	;

function_definition
	: declaration_specifiers declarator declaration_list compound_statement
	| declaration_specifiers declarator compound_statement
	;

declaration_list
	: declaration
	| declaration_list declaration
	;


%%
#include <stdio.h>

extern char yytext[];
extern int column;

void yyerror(char const *s)
{
	fflush(stdout);
	printf("\n%*s\n%*s\n", column, "^", column, s);
}

Thanks, they do record all sessions. They have some waiting time where the sessions are accessible to sponsors only, but after this time they become public.

I will ask Jutta too for permission. B.t.w. the parser generator is here, but I will upload a better version soon.

@codebrainz I think that in void comment(void) the error("unterminated comment"); needs to be yyerror("unterminated comment");. On Cygwin error is defined in libcygwin.a:

$ nm /usr/lib/gcc/x86_64-pc-cygwin/11/../../../../lib/libcygwin.a | grep error -w
0000000000000000 T error

Consider fixing.

Shift reduced conflit in selection_statement with IF ELSE statement

@Siirko it's mentioned in the original source:

Note: There are two shift/reduce conflicts, correctly resolved by default:

IF '(' expression ')' statement _ ELSE statement

and

ATOMIC _ '(' type_name ')'
where "_" has been used to flag the points of ambiguity.

You can quiet the warning using Bison's %nonassoc or %precedence I think.

The grammar does not seem to include simple assignment with a constant?:
Eg.
int result = 1;

The grammar does not seem to include simple assignment with a constant?: Eg. int result = 1;

https://gist.github.com/codebrainz/2933703#file-c99-y-L179

The grammar does not seem to include simple assignment with a constant?: Eg. int result = 1;

https://gist.github.com/codebrainz/2933703#file-c99-y-L179

Yes, but where does it allow for a constant value?

The grammar does not seem to include simple assignment with a constant?: Eg. int result = 1;

https://gist.github.com/codebrainz/2933703#file-c99-y-L179

Yes, but where does it allow for a constant value?

Starting here:

https://gist.github.com/codebrainz/2933703#file-c99-y-L355

Then weaves it's way through the rules from assignment_expression to conditional_expression, to logical_or_expression and so on all the way through the precedence levels to eventually reach primary_expression where it matches CONSTANT. If you have a printer you could try printing it and draw a line through all the rules to see how it gets there after many layers of indirection.

What does the '[' '*' ']' syntax mean?

@AngheloAlf
It is the C99 syntax for a VLA in a function prototype.

it cannot handle string literals in multiple quotes, like this: "multiple""quote""string""literal""

Your example case is too easy. I think about this case:

char const *m =     "Thi"         "s should wo"
       "rk"                                           " t"
       "oo";

I fixed it by using ([LUu]?\"(\\.|[^\\\"\n])*\"[ \f\v\t\r\n]*)*

Then you have to parse the string with a state machine, but you already needed to do that to implement \x61 and \n, \r, \t, etc. This just adds one more bit of state - whether you are in a double-quote or not. Just enforce that the input is only whitespace when not inside a doublequote, and only emit to the resulting string buffer when inside a double-quote. Flex should only give you valid input with my regex fix.