The language is a very small subset of C, supporting the following constructions.

At the top level, we allow only declarations:

• Global variable declarations with integer type (int) and an optional initializer:

int x;
int y = 2+2;
int v,w,z;

We assume that variables without an explicit initializer are implicitly initialized to 0. Function declarations. Functions can return an integer (int) or no value (void). Functions also have a list of integer arguments:

int f(int x, int y)
{
  ...
}

void g()
{
  ...
}

Inside functions, we allow the following instructions:

• Blocks of instructions in curly brackets { ... }.

• Assignments of an integer expression into a variable. Expressions can use the classic integer operators +, -, *, /, %.

Expressions can also call functions. For instance:

x = 2 + 5;
x = 2 * f(x, f(2 * x)-1);

The syntax also supports the shortcuts x++, x--, x += ..., x *= ..., etc.

• Calls to functions returning no argument can appear as stand-alone instructions: g();

Note that supporting function calls (both returning a value and not) is not required as a core feature of your analyzer, but you can offer it as an extension.

• Tests if then or if then else:

if (x==0) x++;
if (x > 0 && x < 100) { x = 2*x; y--; } else { x = 0; y++; }

Note that the condition in the if must be a boolean expression. Boolean expressions are composed of

• atoms comparing two integer expressions with ==,!=, <, >, <=, >=

• atoms combined with the boolean operators !, &&, ||.

Note that, if (x), where x is an integer variable, is supported in C but not in our language. Similarly to Java, you must type if (x!=0).

• Loops can use the while or for standard C constructions (there is no support for do ... while). Here are some examples:

while (a<10) { a = a - 1; }
for (i=0;i<10;i++) x++;
for (;;);

The break instruction can be used to exit the innermost loop:

for (i=0;i<10;i++) {
  while (y<10) {
    if (x>10) break;
    x++; y++;
  }
  // the break jumps here
}

• The return instruction exits the current function. For functions returning an integer, it takes an integer expression as parameter, as in return 2+3;; otherwise, it is just return;.

• Arbitrary jumps inside functions are allowed. A label (destination of a jump) is denoted with a colon, as in a:. A jump is denoted as goto a;. Both forward and backward jumps are allowed. For instance:

x = 0;
loop:
  x = x + 1;
  ...
  if (x > 10) goto exit;
  ...
  goto loop;
exit:
  x = 0;

• Local variable declarations. The syntax is similar to the syntax of global declarations, but the variable is only visible inside the current block.