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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. processes them as if they had been given as arguments.
@xref{Options Summary, ,Summary of Options}. @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 command line variable definitions, and recursion
@cindex variables, command line, and recursion @cindex variables, command line, and recursion
@cindex recursion, and command line variable definitions @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 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 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 @example
subsystem: 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 This is useful when @code{touch} is not enough to make a file appear up
to date. 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{-$(MAKEFLAGS)}.
The @code{findstring} function determines whether one string appears as a The @code{findstring} function determines whether one string appears as a
substring of another. If you want to test for the @samp{-t} flag, substring of another. If you want to test for the @samp{-t} flag, use
use @samp{t} as the first string and the value of @code{MAKEFLAGS} as @samp{t} as the first string and the first word of @code{MAKEFLAGS} as the
the other. other.
For example, here is how to arrange to use @samp{ranlib -t} to finish For example, here is how to arrange to use @samp{ranlib -t} to finish
marking an archive file up to date: marking an archive file up to date:
@example @example
archive.a: @dots{} archive.a: @dots{}
ifneq (,$(findstring t,$(MAKEFLAGS))) ifneq (,$(findstring t,$(word 1,-$(MAKEFLAGS))))
+touch archive.a +touch archive.a
+ranlib -t archive.a +ranlib -t archive.a
else else