URL:
<http://savannah.gnu.org/bugs/?54116>
Summary: Extend documentation for space-free line
continuation techniques
Project: make
Submitted by: drmikehenry
Submitted on: Thu 14 Jun 2018 04:44:07 PM UTC
Severity: 3 - Normal
Item Group: Documentation
Status: None
Privacy: Public
Assigned to: None
Open/Closed: Open
Discussion Lock: Any
Component Version: None
Operating System: None
Fixed Release: None
Triage Status: None
_______________________________________________________
Details:
Line continuations via backslash/newline result in the insertion
of a single space character that often causes problems. I've
discovered a method for suppressing that space which has low
syntactic overhead and is compatible with GNU Make versions as
far back as I can conveniently find. I'd like to propose some
additions to GNU Make's documentation that demonstrate the
technique. I've placed my suggestions on Github here:
https://github.com/drmikehenry/make
I've also attached a diff to this ticket.
There are two techniques documented in the repository above.
First, instead of using backslash/newline for line
continuations, use dollar sign/backslash/newline. After each
backslash-newline has been replaced with a single space, this
leaves dollar sign/space pairs which syntactically expand the
single-character variable named <space>; as that variable is not
defined by default, these pairs evaporate to the empty string.
As a simple example, this:
x := one$\
word
is equivalent to this:
x := oneword
In addition, I've documented a second technique for handling
line continuations. It involves post-processing a multiline
variable to remove newlines and indentation as a way of avoiding
the problems of the injected space character. This method
requires GNU Make 3.80 or later because it uses $(eval) and
$(value), but it results in very readable user-defined
functions.
I've also included a small unit test to help ensure that no
future version of GNU Make will throw warnings or errors when
evaluating the single-character variable named <space>.
My main hope is to ensure that GNU Make does not change in the
future in a way that would break the dollar
sign/backslash/newline technique. Thanks for your
consideration.
Michael Henry
_______________________________________________________
File Attachments:
-------------------------------------------------------
Date: Thu 14 Jun 2018 04:44:07 PM UTC Name: make.diff Size: 5KiB By:
drmikehenry
<http://savannah.gnu.org/bugs/download.php?file_id=44369>
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