Could this be considered acceptable use of goto?

Question

I understand there are few places a goto could be useful, such as embedded for loops or cleanup for multiple function exit points. I was wondering if this could be an acceptable place to do so.

I'm building a regex engine and am using a switch statement to handle each individual character of input. Anything that is not a meta-character goes to the switch's default.

When I read a backslash (\), I want the next character to be escaped and treated literal, i.e. jump directly to the switch's default case. So I thought would it be okay to just goto to the default case by adding another label? Or should I just go the conventional way and separate it into a function?

for(const char* c = regex; *c; c++){
    if(*c == '\\' && *++c)
        goto literal;
    switch(*c){
        case '|':
            ...
        case '*':
            ...
            ...
        default: literal:
            ...
    }
}

Answer 1

It's at least semi-legitimate, but you can write essentially the same code without a goto fairly easily:

for (const char* c = regex; *c; c++)
{
    switch (*c)
    {
    case '|':
        ...
    case '*':
        ...
        ...
    case '\\':
        if (*++c == '\0')
            …report backslash followed by null, probably an error…
        /*FALLTHROUGH*/
    default:
        ...
    }
}

Note that you'd need a case in your original switch to deal with backslash followed by EOS ('\0') anyway.