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3.1.1 Splitting Long Lines
--------------------------

Makefiles use a "line-based" syntax in which the newline character is
special and marks the end of a statement.  GNU 'make' has no limit on
the length of a statement line, up to the amount of memory in your
computer.

   However, it is difficult to read lines which are too long to display
without wrapping or scrolling.  So, you can format your makefiles for
readability by adding newlines into the middle of a statement: you do
this by escaping the internal newlines with a backslash ('\') character.
Where we need to make a distinction we will refer to "physical lines" as
a single line ending with a newline (regardless of whether it is
escaped) and a "logical line" being a complete statement including all
escaped newlines up to the first non-escaped newline.

   The way in which backslash/newline combinations are handled depends
on whether the statement is a recipe line or a non-recipe line.
Handling of backslash/newline in a recipe line is discussed later (*note
Splitting Recipe Lines::).

   Outside of recipe lines, backslash/newlines are converted into a
single space character.  Once that is done, all whitespace around the
backslash/newline is condensed into a single space: this includes all
whitespace preceding the backslash, all whitespace at the beginning of
the line after the backslash/newline, and any consecutive
backslash/newline combinations.

   If the '.POSIX' special target is defined then backslash/newline
handling is modified slightly to conform to POSIX.2: first, whitespace
preceding a backslash is not removed and second, consecutive
backslash/newlines are not condensed.

Splitting Without Adding Whitespace
...................................

If you need to split a line but do _not_ want any whitespace added, you
can utilize a subtle trick: replace your backslash/newline pairs with
the three characters dollar sign, backslash, and newline:

     var := one$\
            word

   After 'make' removes the backslash/newline and condenses the
following line into a single space, this is equivalent to:

     var := one$ word

   Then 'make' will perform variable expansion.  The variable reference
'$ ' refers to a variable with the one-character name " " (space) which
does not exist, and so expands to the empty string, giving a final
assignment which is the equivalent of:

     var := oneword