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COMPILER C
(* An attempt to describe a subset of C *)
CHARACTERS
letter = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz" .
digit = "0123456789" .
hexdigit = digit + "ABCDEFabcdef" .
tab = CHR(9) .
lf = CHR(10) .
eol = CHR(13) .
files = letter + digit + ":\." .
chars = CHR(32) .. CHR(255) - "'" .
strings = CHR(32) .. CHR(255) - '"'.
macros = ANY - eol .
COMMENTS FROM "/*" TO "*/"
IGNORE
tab + eol + lf
TOKENS
identifier = ( "_" | letter) { "_" | letter | digit } .
number = digit { digit } [ "." { digit }] [ "U" | "u" | "L" | "l" ] .
hexnumber = "0" ( "x" | "X" ) hexdigit { hexdigit } [ "U" | "u" | "L" | "l" ] .
string = '"' { strings } '"' .
char = "'" [ "\" ] chars "'" .
library = "<" files { files } ">" .
PRAGMAS
PreProcessor = "#" {macros} .
PRODUCTIONS
C = { Definition } EOF .
(* Variable and Type Definitions *)
Definition = [ StorageClass ] Type { "*" } identifier
( FunctionDefinition | VarList ";" ) .
StorageClass = "auto" | "extern" | "register" | "static" .
Type = "short" [ "int" ]
| "long" [ "int" | "float" ]
| "unsigned" [ "char" | "int" | "long" ]
| "char" | "int" | "float" | "double" | "void" .
VarList = ArraySize { "," { "*" } identifier ArraySize } .
ArraySize = { "[" [ ConstExpression ] "]" } .
(* Function Definitions *)
FunctionDefinition = FunctionHeader ( ";" | FunctionBody ) .
FunctionHeader = "(" [ FormalParamList ] ")" .
FunctionBody = CompoundStatement .
FormalParamList = FormalParameter { "," FormalParameter } .
FormalParameter = Type { "*" } [ identifier ] ArraySize .
(* Statements *)
Statement = { Label }
( AssignmentExpression | BreakStatement
| CompoundStatement | ContinueStatement
| DoStatement | ForStatement
| IfStatement | NullStatement
| ReturnStatement | SwitchStatement
| WhileStatement ) .
Label = "case" ConstExpression ":" | "default" ":" .
(* There is no requirement that a switch statement be followed by a compound
statement. Actually labels may be even more general *)
AssignmentExpression = Expression ";" .
BreakStatement = "break" ";" .
CompoundStatement = "{" { LocalDeclaration } { Statement } "}" .
ContinueStatement = "continue" ";" .
DoStatement = "do" Statement "while" "(" Expression ")" ";" .
ForStatement = "for" "(" [ Expression ] ";" [ Expression ] ";" [ Expression ] ")" Statement .
IfStatement = "if" "(" Expression ")" Statement [ "else" Statement ] .
NullStatement = ";" .
ReturnStatement = "return" [ Expression ] ";" .
(* Expression usually in parentheses *)
SwitchStatement = "switch" "(" Expression ")" Statement .
WhileStatement = "while" "(" Expression ")" Statement .
(* LocalDeclarations *)
LocalDeclaration = [ StorageClass ] Type { "*" } identifier
( FunctionHeader | VarList ) ";" .
(* Expressions, based on Kernighan and Ritchie: "The C Programming Language".
There does not seem to be a way to make this work in an LL(1) fashion,
but this generates a "working" parser *)
ConstExpression = Expression .
Expression = Conditional { AssignmentOperator Expression }.
Conditional = LogORExp .
LogORExp = LogANDExp { "||" LogANDExp } .
LogANDExp = InclORExp { "&&" InclORExp }.
InclORExp = ExclORExp { "|" ExclORExp } .
ExclORExp = ANDExp { "^" ANDExp } .
ANDExp = EqualExp { "&" EqualExp } .
EqualExp = RelationExp { ( "==" | "!=" ) RelationExp } .
RelationExp = ShiftExp { ( "<" | ">" | "<=" | ">=" ) ShiftExp }.
ShiftExp = AddExp { ( "<<" | ">>" ) AddExp } .
AddExp = MultExp { ( "+" | "-" ) MultExp } .
MultExp = CastExp { ( "*" | "/" | "%" ) CastExp } .
CastExp = UnaryExp .
(* we should really add
| "(" identifier ")" CastExp .
but this breaks it badly *)
UnaryExp = PostFixExp
| ( "++" | "--" ) UnaryExp
| UnaryOperator CastExp .
(* we should really add
| "sizeof" ( UnaryExp | "(" Type ")" ) .
but this breaks it badly *)
PostFixExp = Primary
{ "[" Expression "]"
| FunctionCall
| "." identifier
| "->" identifier
| "++"
| "--"
} .
Primary = identifier | string | char | number | "(" Expression ")" .
FunctionCall = "(" [ ActualParameters ] ")" .
ActualParameters = Expression { "," Expression } .
AssignmentOperator = "=" | "*=" | "/=" | "%=" | "+=" | "-=" | "&="
| "^=" | "|=" | "<<=" | ">>=" .
UnaryOperator = "+" | "-" | "*" | "!" | "&" | "~" .
END C.
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