Institutt for Informatikk
Universitetet i Bergen
INF 225 - Innføring i Programoversettelse - H04

Project Part 2 - Recursive-Descent Parser

This part is highly recommended to be solved and handed in groups of two.


You are going to implement in Java, C, or C++ a recursive-descent parser recognising valid C- programs, checking whether the program is type correct, and outputting the syntax tree and symbol table for the program. If the program is invalid, an error message is to be printed. Note, that you have also to design a syntax tree structue for C- suitable for generation by your parser.


You have to hand in your answers no later than Monday October 18th at 12:00 am.

Contents of hand in

The answers handed in must include:

The answers are to be mailed to Magnus Hoff (, no later than the specified deadline. Answers handed in after deadline will NOT be considered.

The program

The program is to read source code for a C- program from standard in, and print the abstract syntax tree and symbol table to standard out after the program having finished. If errors are found in the source code, the program should report the error to standard err. We give some examples of what the output may look like. See Fillager->Project->test_x.c-


Read the C- specifications on page 491-496 very, very carefully!

We also make a few additional specifications:

  1. Local variables shadowing formal parameters are allowed, i.e. you may declare a function with a formal parameter and a local variable of the same name, with the result that the formal parameter is of no use whatsoever. In such a case gcc(1) would issue a warning, but you don't have to check for this.
  2. Void variables, void arrays, and void parameters are not allowed. (A void parameter list is of course allowed.)
  3. Identifiers may not be overloaded within the same scope, i.e., the same identifier cannot be used both for a function and for a global variable. (You may of course declare local variables with the same identifier as a variable or function in an outer scope.)

Error messages

We require the program to continue parsing after some errors:

Symbol table

In the next handin, you will need more attributes for functions and local variables, on top of those required here. It may be wise to take this into account even at this point.

To handle local variables, you may use a stack of symbol tables. When you come to a compound statement, you add a new table on top of the stack, and when you reach the end, you pop the stack. Each node in the syntax tree may keep a reference to the symbol table stack which is valid in this particular node. Thus the symbol tables are available from the syntax tree, even if the parser routines throws them away. To print the symbol table, you may travers the syntax tree and print the top-most table in each node ending a scope.

Type checking


A first example with syntax tree output.