Requirements: Implement a basic interpreter based on Clang
Marking: 25 testcases are provided and each test case counts for 1 mark
Supported Language: We support a subset of C language constructs, as follows:
Type: int | char | void | * Operator: * | + | - | * | / | < | > | == | = | [ ] Statements: IfStmt | WhileStmt | ForStmt | DeclStmt Expr : BinaryOperator | UnaryOperator | DeclRefExpr | CallExpr | CastExpr
We also need to support 4 external functions int GET(), void * MALLOC(int), void FREE (void *), void PRINT(int), the semantics of the 4 funcions are self-explanatory.
A skelton implemnentation ast-interpreter.tgz is provided, and you are welcome to make any changes to the implementation. The provided implementation is able to interpreter the simple program like :
extern int GET(); extern void * MALLOC(int); extern void FREE(void *); extern void PRINT(int);
int main() { int a; a = GET(); PRINT(a); }
We provide a more formal definition of the accepted language, as follows:
Program : DeclList DeclList : Declaration DeclList | empty Declaration : VarDecl FuncDecl VarDecl : Type VarList; Type : BaseType | QualType BaseType : int | char | void QualType : Type * VarList : ID, VarList | | ID[num], VarList | emtpy FuncDecl : ExtFuncDecl | FuncDefinition ExtFuncDecl : extern int GET(); | extern void * MALLOC(int); | extern void FREE(void *); | extern void PRINT(int); FuncDefinition : Type ID (ParamList) { StmtList } ParamList : Param, ParamList | empty Param : Type ID StmtList : Stmt, StmtList | empty Stmt : IfStmt | WhileStmt | ForStmt | DeclStmt | CompoundStmt | CallStmt | AssignStmt | IfStmt : if (Expr) Stmt | if (Expr) Stmt else Stmt WhileStmt : while (Expr) Stmt DeclStmt : Type VarList; AssignStmt : DeclRefExpr = Expr; CallStmt : CallExpr; CompoundStmt : { StmtList } ForStmt : for ( Expr; Expr; Expr) Stmt Expr : BinaryExpr | UnaryExpr | DeclRefExpr | CallExpr | CastExpr | ArrayExpr | DerefExpr | (Expr) | num BinaryExpr : Expr BinOP Expr BinaryOP : + | - | * | / | < | > | == UnaryExpr : - Expr DeclRefExpr : ID CallExpr : DeclRefExpr (ExprList) ExprList : Expr, ExprList | empty CastExpr : (Type) Expr ArrayExpr : DeclRefExpr [Expr] DerefExpr : * DeclRefExpr
input example: ./ast-interpreter cat test00.c
finish: 25/25