| Locally Declared Labels

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Each statement expression is a scope in which local labels can be declared. A local label is simply an identifier; you can jump to it with an ordinary `goto` statement, but only from within the statement expression it belongs to.
A local label declaration looks like this:

    __label__ label;

or

    __label__ label1, label2, /* ... */;

Local label declarations must come at the beginning of the statement expression, right after the `({`, before any ordinary declarations.
The label declaration defines the label name, but does not define the label itself. You must do this in the usual way, with `label:`, within the statements of the statement expression.
The local label feature is useful because statement expressions are often used in macros. If the macro contains nested loops, a `goto` can be useful for breaking out of them. However, an ordinary label whose scope is the whole function cannot be used: if the macro can be expanded several times in one function, the label will be multiply defined in that function. A local label avoids this problem. For example:

    #define SEARCH(array, target)                     \
    ({                                                \
      __label__ found;                                \
      typeof (target) _SEARCH_target = (target);      \
      typeof (*(array)) *_SEARCH_array = (array);     \
      int i, j;                                       \
      int value;                                      \
      for (i = 0; i < max; i++)                       \
        for (j = 0; j < max; j++)                     \
          if (_SEARCH_array[i][j] == _SEARCH_target)  \
            { value = i; goto found; }                \
      value = -1;                                     \
     found:                                           \
      value;                                          \
    })