How to store goto labels in an array and then jump to them?

Question

I want to declare an array of \"jumplabels\".

Then I want to jump to a \"jumplabel\" in this array.

But I have not any idea how to do this.

It should

Answer 1

For a simple answer, instead of forcing compilers to do real stupid stuff, learn good programming practices.

Answer 2

There's no direct way to store code addresses to jump to in C. How about using switch.

#define jump(x)  do{ label=x; goto jump_target; }while(0)
int label=START;
jump_target:
switch(label)
{
    case START:
        /* ... */
    case LABEL_A:
        /* ... */
}

You can find similar code produced by every stack-less parser / state machine generator. Such code is not easy to follow so unless it is generated code or your problem is most easily described by state machine I would recommend not do this.

Answer 3

Tokenizer? This looks like what gperf was made for. No really, take a look at it.

Answer 4

could you use function pointers instead of goto?

That way you can create an array of functions to call and call the appropriate one.

Answer 5

That's what switch statements are for.

switch (var)
{
case 0:
    /* ... */
    break;
case 1:
    /* ... */
    break;
default:
    /* ... */
    break;  /* not necessary here */
}

Note that it's not necessarily translated into a jump table by the compiler.

If you really want to build the jump table yourself, you could use a function pointers array.

Answer 6

In plain standard C, this not possible as far as I know. There is however an extension in the GCC compiler, documented here, that makes this possible.

The extension introduces the new operator &&, to take the address of a label, which can then be used with the goto statement.