Output Format for Code Generator

MIL Intermediate Code

In the event that there are no lexical, syntactic, or semantic errors in the inputted MINI-L program, your code generator should output the generated MIL program on stdout. Refer to the specification of the MIL intermediate code representation for more details about MIL code.

Semantic Error Messages

There are nine types of semantic errors that should be captured by your code generator if they are present in an inputted MINI-L program.

  1. Using a variable without having first declared it.
  2. Calling a function which has not been defined.
  3. Not defining a main function.
  4. Defining a variable more than once (it should also be an error to declare a variable with the same name as the MINI-L program itself).
  5. Trying to name a variable with the same name as a reserved keyword.
  6. Forgetting to specify an array index when using an array variable (i.e., trying to use an array variable as a regular integer variable).
  7. Specifying an array index when using a regular integer variable (i.e., trying to use a regular integer variable as an array variable).
  8. Declaring an array of size <= 0.
  9. Using continue statement outside a loop.

Note that some of the above semantic errors may actually cause syntax errors during parsing. For example, if you try to declare a variable with a keyword name, then that will most likely cause a syntax error during parsing. That is fine. What is important is that some type of error message is emitted if any of the above errors are present.

If there are multiple occurrences of the above errors, your code generator should output an error message for each encountered error. You are free to choose the particular format of each error message. At a minimum, each error message should include the source code line number at which the error is encountered. If at least one error is encountered, then no intermediate code should be generated.

As an example, consider the following MINI-L program. 

1. function main;
2. beginparams
3. endparams
4. beginlocals
5. 	n : integer;
6. 	r : array [10] of integer;
7. 	n : array [10] of integer;
8. endlocals
9. beginbody
10. 	read n;
11. 	n := z + 1;
12. 	n := n + r;
13. 	write n;
14. 	continue;
15. endbody

In the above program, there are four semantic errors occurring at lines 7, 11, 12 and 14. The corresponding error messages that might be emitted by your code generator are shown below. 

Error line 7: symbol "n" is multiply-defined.
Error line 11: used variable "z" was not previously declared.
Error line 12: used array variable "r" is missing a specified index.
Error line 14: continue statement not within a loop.

Error files errors.min and custom.min can be used for testing.