+=== Filling
+
+A _filling_ represents zero or more padding bytes to make the
+<<cur-offset,current offset>> reach a given value.
+
+A filling is:
+
+. The ``pass:[+]`` prefix.
+
+. One of:
+
+** A positive integer (hexadecimal starting with `0x` or `0X` accepted)
+ which is the current offset target.
+
+** The ``pass:[{]`` prefix, a valid {py3} expression of which the
+ evaluation result type is `int` or `bool` (automatically converted to
+ `int`), and the ``pass:[}]`` suffix.
++
+For a filling at some source location{nbsp}__**L**__, this expression
+may contain:
++
+--
+* The name of any <<label,label>> defined before{nbsp}__**L**__
+ which isn't within a nested group.
+* The name of any <<variable-assignment,variable>> known
+ at{nbsp}__**L**__.
+--
++
+The value of the special name `ICITTE` (`int` type) in this expression
+is the <<cur-offset,current offset>> (before handling the items to
+repeat).
+
+** A valid {py3} name.
++
+For the name `__NAME__`, this is equivalent to the
+`pass:[{]__NAME__pass:[}]` form above.
+
++
+This value must be greater than or equal to the current offset where
+it's used.
+
+. **Optional**:
++
+--
+. The ``pass:[~]`` prefix.
+. A positive integer (hexadecimal starting with `0x` or `0X` accepted)
+ which is the value of the byte to use as padding to reach the
+ current offset target.
+--
++
+Without this section, the padding byte value is zero.
+
+====
+Input:
+
+----
+aa bb cc dd
++0x40
+"hello world"
+----
+
+Output:
+
+----
+aa bb cc dd 00 00 00 00 00 00 00 00 00 00 00 00 ┆ ••••••••••••••••
+00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ┆ ••••••••••••••••
+00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ┆ ••••••••••••••••
+00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ┆ ••••••••••••••••
+68 65 6c 6c 6f 20 77 6f 72 6c 64 ┆ hello world
+----
+====
+
+====
+Input:
+
+----
+!macro part(iter, fill)
+ <0> "particular security " {ord('0') + iter : 8} +fill~0x80
+!end
+
+{iter = 1}
+
+!repeat 5
+ m:part(iter, {32 + 4 * iter})
+ {iter = iter + 1}
+!end
+----
+
+Output:
+
+----
+70 61 72 74 69 63 75 6c 61 72 20 73 65 63 75 72 ┆ particular secur
+69 74 79 20 31 80 80 80 80 80 80 80 80 80 80 80 ┆ ity 1•••••••••••
+80 80 80 80 70 61 72 74 69 63 75 6c 61 72 20 73 ┆ ••••particular s
+65 63 75 72 69 74 79 20 32 80 80 80 80 80 80 80 ┆ ecurity 2•••••••
+80 80 80 80 80 80 80 80 80 80 80 80 70 61 72 74 ┆ ••••••••••••part
+69 63 75 6c 61 72 20 73 65 63 75 72 69 74 79 20 ┆ icular security
+33 80 80 80 80 80 80 80 80 80 80 80 80 80 80 80 ┆ 3•••••••••••••••
+80 80 80 80 80 80 80 80 70 61 72 74 69 63 75 6c ┆ ••••••••particul
+61 72 20 73 65 63 75 72 69 74 79 20 34 80 80 80 ┆ ar security 4•••
+80 80 80 80 80 80 80 80 80 80 80 80 80 80 80 80 ┆ ••••••••••••••••
+80 80 80 80 80 80 80 80 70 61 72 74 69 63 75 6c ┆ ••••••••particul
+61 72 20 73 65 63 75 72 69 74 79 20 35 80 80 80 ┆ ar security 5•••
+80 80 80 80 80 80 80 80 80 80 80 80 80 80 80 80 ┆ ••••••••••••••••
+80 80 80 80 80 80 80 80 80 80 80 80 ┆ ••••••••••••
+----
+====
+