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[SV 62496] Fix example of testing MAKEFLAGS

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* doc/make.texi (Options/Recursion): Define the layout of MAKEFLAGS.
(Testing Flags): Fix the example to test the first word.
This commit is contained in:
Paul Smith 2022-08-03 00:05:39 -04:00
parent 7ad2593b2d
commit 91d87ccf32
1 changed files with 18 additions and 5 deletions
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doc/make.texi
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@ -4957,6 +4957,13 @@ in its environment. In response, it takes the flags from that value and
processes them as if they had been given as arguments.
@xref{Options Summary, ,Summary of Options}.
The value of @code{MAKEFLAGS} is a possibly empty group of characters
representing single-letter options that take no argument, followed by a space
and any options that take arguments or which have long option names. If an
option has both single-letter and long options, the single-letter option is
always preferred. If there are no single-letter options on the command line,
then the value of @code{MAKEFLAGS} starts with a space.
@cindex command line variable definitions, and recursion
@cindex variables, command line, and recursion
@cindex recursion, and command line variable definitions
@ -5006,7 +5013,7 @@ meaning to run as many jobs as possible in parallel, this is passed
down, since multiple infinities are no more than one.@refill
If you do not want to pass the other flags down, you must change the
value of @code{MAKEFLAGS}, like this:
value of @code{MAKEFLAGS}, for example like this:
@example
subsystem:
@ -7209,17 +7216,23 @@ You can write a conditional that tests @code{make} command flags such as
This is useful when @code{touch} is not enough to make a file appear up
to date.
Recall that @code{MAKEFLAGS} will put all single-letter options (such as
@samp{-t}) into the first word, and that word will be empty if no
single-letter options were given. To work with this, it's helpful to add a
value at the start to ensure there's a word: for example
@samp{-$(MAKEFLAGS)}.
The @code{findstring} function determines whether one string appears as a
substring of another. If you want to test for the @samp{-t} flag,
use @samp{t} as the first string and the value of @code{MAKEFLAGS} as
the other.
substring of another. If you want to test for the @samp{-t} flag, use
@samp{t} as the first string and the first word of @code{MAKEFLAGS} as the
other.
For example, here is how to arrange to use @samp{ranlib -t} to finish
marking an archive file up to date:
@example
archive.a: @dots{}
ifneq (,$(findstring t,$(MAKEFLAGS)))
ifneq (,$(findstring t,$(word 1,-$(MAKEFLAGS))))
+touch archive.a
+ranlib -t archive.a
else