Semantic Analyzer

Issues

• TRUE PLUS FALSE -> accepted by Syntax Analyzer, so resolve here
• Resolve Arithmetic and Boolean Expr ambiguity

Problems that can't be addressed by a CFG:

1. Is x scalar, an array, or a function?
2. Is x declared before it is used?
3. Is x defined before it is used?
4. Are any names declared but not used?
5. Which declaration of x is being referenced?
6. Is an expression type-consistent?
7. What is the meaning of res= a+b*c? When a is integer, b and c are of float type.
8. Does the dimension of a reference match the declaration?
9. Where can x be stored? (heap, stack, ...)
10. Does *p reference the result of a malloc()?
11. Is an array reference in bounds?
12. Does function foo produce a constant value?

Some more issues we need to consider

• Consider the following program:

1. fie(a,b,c,d)
2. int a, b, c, d;
3. { … }
4. fee()
5. {
6. int f[3], g[10], h, i, j, k;
7. char *p;
8. call fie(h, i, “ab”, j, k);
9. k = f * i + j;
10. h = g[17];
11. printf(“<%s,%s>.\n”,p,q);
12. p = 10 + ‘c’;
13. If( i = i+4)
14. }

• Issues:
  • declared g[10], used g[17]
  • wrong number of args to fie()
  • “ab” is not an int
  • wrong dimension on use of f
  • undeclared variable q
  • 10 is not a character string