I was reading through the documentation of GNU/GCC and I stopped at the description of __attribute__ ((packed)).
It says:

packed
    The packed attribute specifies that a variable or structure field should have the smallest possible alignment—one byte for a variable, and one bit for a field, unless you specify a larger value with the aligned attribute.

    Here is a structure in which the field x is packed, so that it immediately follows a:

              struct foo
              {
                char a;
                int x[2] __attribute__ ((packed));
              };

I wonder how this attribute works exactly and whether this code:

struct foo
{
char a:1 __attribute__ ((packed));
};

would create a 1-bit structure instead of 1-byte.