什么是间接goto声明？

Question

In Clang API, there is a GotoStmt and an IndirectGotoStmt . There is very little explanation on the difference between these two kinds of goto statments. I know what a goto label; statement is. But what is an indirect goto statement ? I want to know what that is in the context of C/C++ code, not necessarily just Clang. What does it mean syntactically to have an indirect goto statement ? Can you provide a code example?

Edit: The following question is interesting.

Can you make a computed goto in C++

Answer 1

There is a GNU extension that allows taking an address of a label, storing it for later use, then goto that address at a later point. See https://gcc.gnu.org/onlinedocs/gcc/Labels-as-Values.html for details. Example:

    void *ptr;

    if(...)
        ptr = &&foo;
    else
        ptr = &&bar;

    /* ... */
    goto *ptr;

foo:
    /* ... */

bar:
    /* ... */

Clang supports that too, as it aims at being compatible with GCC.

The use of the above might be, for example, in implementing state machines.