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Miscellaneous changes by Richard Stallman, added `$$@' to the

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list of unsupported features.
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Roland McGrath 1988-05-15 18:58:00 +00:00
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@ -6,7 +6,11 @@
$Header$
$Log$
Revision 1.15 1988/05/11 21:30:52 mcgrath
Revision 1.16 1988/05/15 18:58:00 mcgrath
Miscellaneous changes by Richard Stallman, added `$$@' to the
list of unsupported features.
Revision 1.15 88/05/11 21:30:52 mcgrath
* Made `$<' automatic variable be the first dependency of any rule.
* Bumped revision number to correspond to `make.c'.
@ -66,7 +70,7 @@ This version of the documentation is accurate for revision 1.2 of the source.
@ifinfo
This file documents the GNU Make utility.
Copyright @copyright{} 1988 Free Software Foundation, Inc.
Copyright (C) 1988 Free Software Foundation, Inc.
Permission is granted to make and distribute verbatim copies of
this manual provided the copyright notice and this permission notice
@ -166,27 +170,28 @@ be recompiled, or how. @xref{Running}.
* Commands:: A rule contains shell commands that say how to remake.
* Variables:: A variable holds a text string for substitution into rules.
* Conditionals::Makefiles that do one thing or another depending on
variable values.
variable values.
* Functions:: Functions can do text-processing within @code{make}.
* Running:: How to run @code{make}; how you can adjust the way
@code{make} uses the makefile.
@code{make} uses the makefile.
* Implicit:: Implicit rules take over if the makefile doesn't say
how a file is to be remade.
how a file is to be remade.
* Archives:: How to use @code{make} to update archive files.
* Missing:: Features of other @code{make}s not supported by GNU @code{make}.
* Concept Index::Index of cross-references to where concepts are discussed.
* Name Index:: Index of cross-references for names of @code{make}'s
variables, functions, special targets and directives.
variables, functions, special targets and directives.
@end menu
@node Bugs,, Top, Top
@section Problems and Bugs
If you have problems with GNU @code{make} or think you've found a bug,
please report it to Roland McGrath; he will probably do something about it.
please report it to Roland McGrath; he doesn't promise to do anything
but he might well want to fix it.
Before reporting a bug, make sure you've actually found a real bug.
Carefully re-read the documentation and see if it really says you can do
@ -194,19 +199,18 @@ what you're trying to do. If it's not clear whether you should be able
to do something or not, report that too; it's a bug in the documentation!
Before reporting a bug or trying to fix it yourself, try to isolate it to
the smallest possible makefile that reproduces the problem. Then send me
the makefile, the exact results @code{make} gave you and tell me what you
expected to get. You may be misunderstanding the documentation and
thinking you can do something you can't, in which case I need to know
what you thought so I can fix the documentation.@refill
the smallest possible makefile that reproduces the problem. Then send
the makefile, the exact results @code{make} gave you. Also say what
you expected to occur; this will help us decide whether the problem
was in the documentation.
Once you've got a precise problem, send me electronic mail at Internet
address @samp{roland@@wheaties.ai.mit.edu} or UUCP path
@samp{mit-eddie!wheaties.ai.mit.edu!roland}. Please include the version
number of @code{make} you are using. You can get this information with
the command @samp{make -v -f /dev/null}.@refill
Once you've got a precise problem, send electronic mail to Internet
address @samp{bug-gnu-utils@@prep.ai.mit.edu} or UUCP path
@samp{mit-eddie!prep.ai.mit.edu!bug-gnu-utils}. Please include the version
number of @code{make} you are using. You can get this information with the
command @samp{make -v -f /dev/null}.@refill
Non-bug questions and suggestions are always welcome as well.
Non-bug suggestions are always welcome as well.
@node Simple, Makefiles, Bugs, Top
@section Simple Example of @code{make}
@ -549,10 +553,10 @@ common set of variable definitions (@pxref{Setting}) or pattern rules
(@pxref{Pattern Rules}).
Another such occasion is when you want to automatically generate
dependencies from source files; the dependencies can be put in a file
that is included by the main makefile. This practice is generally
cleaner than that of somehow appending the dependencies to the end of the
main makefile as has been traditionally done with other versions of @code{make}.
dependencies from source files; the dependencies can be put in a file that
is included by the main makefile. This practice is generally cleaner than
that of somehow appending the dependencies to the end of the main makefile
as has been traditionally done with other versions of @code{make}.
If the specified name does not start with a slash, and the file is not
found in the current directory, several other directories are searched.
@ -834,13 +838,30 @@ there is no need to write explicit rules for compiling the files.)
@node Directory Search, Phony Targets, Wildcards, Rules
@section Searching Directories for Dependencies
@vindex VPATH
@vindex vpath
@cindex @code{vpath} pattern
@cindex @code{vpath} search path
@findex vpath
@cindex vpath
@cindex search path for dependencies
@cindex directory search
For large systems, it is often desirable to put sources in a separate
directory from the binaries. The @code{VPATH} feature makes this easier.
directory from the binaries. The @dfn{directory search} features of
@code{make} facilitate this by searching several directories automatically
to find a dependency. When you redistribute the files among directories,
you do not need to change the individual rules, just the search paths.
@menu
* General Search:: The @code{VPATH} variable specifies a search path
that applies to every dependency.
* Selective Search:: The @code{vpath} directive specifies a search path
for a specified class of names.
* Commands/Search:: How to write shell commands that work together
with search paths.
* Implicit/Search:: How search paths affect implicit rules.
* Libraries/Search:: Directory search for link libraries.
@end menu
@node General Search, Selective Search, Directory Search, Directory Search
@subsection @core{VPATH}: Search Path for All Dependencies
The value of the variable @code{VPATH} is a list of directories which
@code{make} should search (in the order specified) for dependency files.
@ -853,11 +874,11 @@ VPATH = src:../headers
@noindent
specifies a path containing two directories, @file{src} and @file{../headers}.
When a file listed as a dependency does not exist in the current directory,
the directories listed in @code{VPATH} are searched for a file with that
name. If a file is found in one of them, that file becomes the dependency.
Rules may then specify the names of source files as if they all existed in
the current directory.
Whenever a file listed as a dependency does not exist in the current
directory, the directories listed in @code{VPATH} are searched for a file
with that name. If a file is found in one of them, that file becomes the
dependency. Rules may then specify the names of source files as if they
all existed in the current directory.
Using the value of @code{VPATH} set in the previous example, a rule like this:
@ -876,10 +897,61 @@ foo.o : src/foo.c
assuming the file @file{foo.c} does not exist in the current directory but
is found in the directory @file{src}.
But what about the rule's commands? The @code{VPATH} directory search
cannot change the commands; they will execute as written. You need to
write the commands so that they will use the file names that @code{make}
finds. This is done with the @dfn{automatic variables} such as @samp{$^}
@node Selective Search, Commands/Search, General Search, Directory Search
@subsection The @code{vpath} Directive
Similar to the @code{VPATH} variable but more selective is the @code{vpath}
directive, which allows you to specify a search path for a particular class
of filenames, those that match a particular pattern. Thus you can supply
certain search directories for one class of filenames and other directories
(or none) for other filenames.
There are three forms of the @code{vpath} directive:
@table @code
@item vpath @var{pattern} @var{directories}
Specify the search path @var{directories} for filenames that match
@code{pattern}. If another path was previously specified for the same
pattern, the new path replaces it. Note that it does @emph{not} add
to the old path for this pattern.@refill
The search path, @var{directories}, is a colon-separated list of
directories to be searched, just like the search path used in the
@code{VPATH} variable.
@item vpath @var{pattern}
Clear out the search path associated with @var{pattern}.
@item vpath
Clear all search paths previously specified with @code{vpath} directives.
@end table
A @code{vpath} pattern is a string containing a @samp{%} character. The
string must match the filename of a dependency that is being searched for,
the @samp{%} character matching any sequence of zero or more characters (as
in pattern rules; @pxref{Pattern Rules}). (It is valid to omit the
@samp{%}, but then the pattern must match the dependency exactly, which may
not be very useful.)
When a dependency fails to exist in the current directory, if the
@var{pattern} in a @code{vpath} directive matches the name of the
dependency file, then the @var{directories} in that directive are searched
just like (and before) the directories in the @code{VPATH} variable.@refill
If several @code{vpath} patterns match the dependency file's name, then
@code{make} processes each matching @code{vpath} directive one by one,
searching all the directories mentioned in each directive. The @code{vpath}
directives are processed in the order in which they appear in the makefiles.
@node Commands/Search, Implicit/Search, Selective Search, Directory Search
@subsection Writing Shell-Commands with Directory Search
When a dependency is found in another directory through directory search,
this cannot change the commands of the rule; they will execute as written.
Therefore, you must write the commands with care so that they will look for
the dependency in the directory where @code{make} finds it.
This is done with the @dfn{automatic variables} such as @samp{$^}
(@pxref{Automatic}). For instance, the value of @samp{$^} is a list of all
the dependencies of the rule, including the names of the directories in
which they were found, and the value of @samp{$@@} is the target. Thus:
@ -891,49 +963,8 @@ foo.o : foo.c
@noindent
The variable @code{CFLAGS} exists so you can specify flags for C
compilation by changing its value; we use it here for consistency so it
will affect all C compilations uniformly. (@pxref{Implicit Variables}).
A similar but more general feature is the @code{vpath} directive, which
allows you to specify a search path for a particular class of filenames,
those that match a particular pattern. Thus you can supply certain
search directories for one class of filenames and other directories (or
none) for other filenames.
There are three forms of the @code{vpath} directive:
@table @code
@item vpath @var{pattern} @var{directories}
Specify the search path @var{directories} for filenames that match
@code{pattern}. If another path was previously specified for the same
pattern, the new path replaces it. Note that it does @emph{not} add to
the old path.@refill
@item vpath @var{pattern}
Clear out the search path associated with @var{pattern}.
@item vpath
Clear all search paths previously specified with @code{vpath} directives.
@end table
A @code{vpath} pattern is a string containing a @samp{%} character.
The string must match the filename of a dependency that is being searched
for, the @samp{%} character matching any sequence of zero or more
characters (as in pattern rules; @pxref{Pattern Rules}).
(Actually the @samp{%} may be left out, necessitating an exact match.)
A @code{vpath} search path is a colon-separated list of directories to be
searched, just like the search path used in the @code{VPATH} variable.
When a dependency needs to be sought outside of tfhe current directory,
if the @var{pattern} in a @code{vpath} directive matches the name of the
dependency file, then the @var{directories} in that directive are
searched just like (and before) the directories in the @code{VPATH}
variable.@refill
If several @code{vpath} patterns match the dependency file's name, then
@code{make} processes each matching @code{vpath} directive one by one,
searching all the directories mentioned in each directive. The @code{vpath}
directives are processed in the order in which they appear in the makefiles.
compilation by implicit rule; we use it here for consistency so it will
affect all C compilations uniformly. (@pxref{Implicit Variables}).
Often the dependencies include header files as well, which you don't want
to mention in the commands. The function @code{firstword} can be used to
@ -941,38 +972,50 @@ extract just the first dependency from the entire list, as shown here
(@pxref{Filename Functions}):
@example
VPATH = src:../headers
foo.o : foo.c defs.h hack.h
cc -c $(CFLAGS) $(firstword $^) -o $@@
@end example
@noindent
Here the value of @samp{$^} is something like @samp{src/foo.c
Here the value of @samp{$^} would be something like @samp{src/foo.c
../headers/defs.h hack.h}, from which @samp{$(firstword $^)} extracts just
@samp{src/foo.c}.@refill
@node Implicit/Search, Libraries/Search, Commands/Search, Directory Search
@subsection Directory Search and Implicit Rules
The search through the directories in @code{VPATH} happens also during
consideration of implicit rules (@pxref{Implicit}).
The search through the directories specified in @code{VPATH} or with
@code{vpath} happens also during consideration of implicit rules
(@pxref{Implicit}).
For example, when a file @file{foo.o} has no explicit rule, @code{make}
considers implicit rules, such as to compile @file{foo.c} if that file
exists. If such a file is lacking in the current directory, the
directories in @code{VPATH} are searched for it. If @file{foo.c} exists
(or is mentioned in the makefile) in any of the directories, the implicit
rule for C compilation is applicable.
appropriate directories are searched for it. If @file{foo.c} exists (or is
mentioned in the makefile) in any of the directories, the implicit rule for
C compilation is applicable.
The commands of all the built-in implicit rules normally use automatic
variables as a matter of necessity; consequently they will use the file
names found by directory search with no extra effort.
There is a final rather obscure little feature of directory search.
It is designed especially for libraries. A dependency name of the form
@code{-l@var{name}} will be searched for under the filename
@samp{lib@var{name}.a} in the @samp{/lib} and @samp{/usr/lib} directories
and then will be searched for in matching @code{vpath} search paths and in
the @code{VPATH} search path. This is meant to facilitate the use of
libraries in makefiles. For example,@refill
@node Libraries/Search,, Implicit/Search, Directory Search
@subsection Directory Search for Link Libraries
Directory search applies in a special way to libraries used with the
linker. This special feature comes into play when you write a dependency
whose name is of the form @code{-l@var{name}}. (You can tell something
funny is going on here because the dependency is normally the name of a
file, and the @emph{file name} of the library looks like
@file{lib@var{name}.a}, not like @code{-l@var{name}}.)@refill
When a dependency's name has the form @code{-l@var{name}}, @code{make}
handles it specially by searching for the file @samp{lib@var{name}.a} in
the directories @samp{/lib} and @samp{/usr/lib}, and then using matching
@code{vpath} search paths and the @code{VPATH} search path.@refill
For example,
@example
foo : foo.c -lcurses
@ -980,12 +1023,9 @@ foo : foo.c -lcurses
@end example
@noindent
would cause the command @samp{cc foo.c -lcurses -o foo} to be executed
when @samp{foo} is older than @samp{foo.c} or any of
@samp{/lib/libcurses.a} @samp{/usr/lib/libcurses.a} or the file
@samp{libcurses.a} in any of the directories in @code{vpath} search paths
whose associated patterns match @samp{libcurses.a} or in any of the
directories in the @code{VPATH} search path.@refill
would cause the command @samp{cc foo.c -lcurses -o foo} to be executed when
@file{foo} is older than @file{foo.c} or than @file{libcurses.a} (which has
probably been found by directory search in @file{/usr/lib/libcurses.a}).@refill
As shown by the example above, the file name found by directory search is
used only for comparing the file time with the target file's time. It
@ -1606,7 +1646,10 @@ the form:
@example
make: Entering directory `/u/gnu/make'.
@end example
before doing anything else, and a line of the form
@noindent
before doing anything else, and a line of this form:
@example
make: Leaving directory `/u/gnu/make'.
@end example
@ -1649,9 +1692,9 @@ rule's target file name.
To use the canned sequence, substitute the variable into the commands of a
rule. You can substitute it like any other variable (@pxref{Reference}).
Because the variable assignment made by a @code{define} is to a
recursively expanded variable, variable references inside such a variable
are expanded when the commands are run. For example:
Because variables defined by @code{define} are recursively expanded
variables, all the variable references you wrote inside the @code{define}
are expanded now. For example:
@example
foo.c : foo.y
@ -1756,7 +1799,7 @@ variables (@pxref{Automatic}).
In addition to simple references, variables can be referenced in manners
which modify the value of the reference but do not modify the value of
the variable referenced. There are two categories of modified references:
substitution references and conditional references.@refill
@dfn{substitution references} and @dfn{conditional references}.@refill
A @dfn{substitution reference} is really a simplified form of the
@code{patsubst} expansion function (@pxref{Functions}). It has the form
@ -1775,7 +1818,7 @@ sets @samp{bar} to @samp{a.c b.c c.c}. @xref{Setting}.
@dfn{Conditional references} are references whose value depends on
whether or not some variable is set. They are inspired by the similar
construct in the shell @samp{sh}. The syntax of conditional references is:
construct in the shell @code{sh}. The syntax of conditional references is:
@table @code
@item $(@var{a}:-@var{b})
@ -1784,17 +1827,22 @@ This expands to the value of the variable @var{a} if it is defined or to
@item $(@var{a}:+@var{b})
This expands to @samp{@var{b}} if the variable @var{a} is
defined or nothing if it is not.
defined or to nothing (no characters) if it is not.
@item $(@var{a}:@var{b}-@var{c})
This expands to @samp{@var{b}} if the variable @var{a} is defined or to
@samp{@var{c}} (a literal string) if it is not.
@end table
For the purpose of these conditional references, a variable is
@dfn{defined} if it exists and is non-null. If the @samp{:} is left out
of these, a variable need not be non-null to be considered @dfn{defined}.
Note that a variable consisting solely of whitespace is @emph{not} null.
For the purpose of these conditional references, a variable is ``defined''
if it exists and is non-null.
In the first two alternatives, the @samp{:} may be omitted. Then the
variable @var{a} is considered ``defined'' if it has been assigned any
value, even a null value.
Note that a variable value consisting solely of whitespace is @emph{not}
null.
@node Values, Flavors, Reference, Variables
@section How Variables Get Their Values
@ -1838,8 +1886,10 @@ Variables of this sort are defined by lines using @samp{=}.
@iftex
(See the next section.)
@end iftex
When the definition is made, the value given is not expanded for variable
references. When the variable is expanded, the value is expanded recursively.
The value you specify is installed verbatim; if it contains references to
other variables, these references are expanded whenever this variable is
substituted (in the course of expanding some other string). When this
happens, it is recursive expansion.
For example,
@ -1855,8 +1905,9 @@ all:;echo $(foo)
will echo @samp{Huh?}: @code{$(foo)} expands to @code{$(bar)} which
expands to @code{$(ugh)} which finally expands to @samp{Huh?}.@refill
This flavor of variable has its advantages and its disadvantages.
An advantage (most would say) is that
This flavor of variable is the only sort supported by other versions of
@code{make}. It has its advantages and its disadvantages. An advantage
(most would say) is that
@example
CFLAGS = $(include_dirs) -O
@ -1873,12 +1924,13 @@ CFLAGS = $(CFLAGS) -O
@end example
@noindent
because it will cause an infinite loop in the variable expansion.
Another disadvantage is that functions (@pxref{Functions}) will be executed
every time a variable calling a function is expanded and this wastes a lot
of time. As well as wasting time, this will give unpredictable results
when using the @code{wildcard} function. This flavor of variable is the
only sort supported by other versions of @code{make}.@refill
because it will cause an infinite loop in the variable expansion. (Actually
@code{make} detects the infinite loop and reports an error.)
Another disadvantage is that any functions (@pxref{Functions}) referenced
in the definition will be executed every time the variable is expanded.
This makes @code{make} run slower; worse, it causes the @code{wildcard}
function to give unpredictable results.
To avoid all the problems and inconveniences of recursively expanded
variables, there is another flavor: @dfn{simply expanded} variables.
@ -1889,35 +1941,40 @@ Simply expanded variables are defined by lines using @samp{:=}.
@iftex
(See the next section.)
@end iftex
When a simply expanded variable is defined, the value it is given is
expanded before the definition is made. When variables of this flavor
are expanded, they are expanded only once, not recursively.@refill
Thus,
The value of a simply expanded variable is scanned once and for all,
expanding any references to other variables and functions, when the
variable is defined. The actual value of the simply expanded variable is
the result of expanding the value you write. It does not contain any
references to other variables; it contains their values @emph{as of the
time this variable was defined}. Therefore,
@example
x := foo
y := $(x) bar
x := later
@end example
@noindent
is equivalent to
@example
x := foo
y := foo bar
x := later
@end example
This method makes complicated makefile programming easier. It allows you
to redefine a variable using its own value (or its value processed in some
way by one of the expansion functions; @pxref{Functions}) and to use the
variable expansion functions much more efficiently.
When a simply expanded variable is referenced, its value is substituted
verbatim.
It also gives you a way to introduce leading or trailing spaces into variable
values. Such spaces are discarded from your input before substitution of
variable references and function calls; this means you can include leading
or trailing spaces in a variable value by protecting them with variable
references, like this:
Simply expanded variables generally make complicated makefile programming
more predictable. This way you can redefine a variable using its own value
(or its value processed in some way by one of the expansion functions;
@pxref{Functions}) and use the expansion functions much more efficiently.
You can also use them to introduce controlled leading or trailing spaces
into variable values. Such spaces are discarded from your input before
substitution of variable references and function calls; this means you can
include leading or trailing spaces in a variable value by protecting them
with variable references, like this:
@example
nullstring :=
@ -1927,7 +1984,6 @@ space := $(nullstring) $(nullstring)
@noindent
Here the value of the variable @code{space} is precisely one space.
@node Setting, Override Directive, Flavors, Variables
@section Setting Variables
@cindex setting variables
@ -1986,7 +2042,6 @@ or
override @var{variable} := @var{value}
@end example
The @code{override} directive was not invented for escalation in the war
between makefiles and command arguments. It was invented so you can alter
and add to values that the user specifies with command arguments.
@ -2006,16 +2061,16 @@ override CFLAGS := $(CFLAGS) -g
@findex endef
Another way to set the value of a variable is to use the @code{define}
directive. This directive has a different syntax and provides different
features, and its intended use is for defining canned sequences of commands
(@pxref{Sequences}). But the variables made with @code{define} are just
like those made the usual way. Only the variable's value matters.
directive. This directive has a different syntax which allows newline
characters to be included in the value, which is convenient for defining
canned sequences of commands (@pxref{Sequences}).
The @code{define} directive is followed on the same line the name of the
variable and nothing more. The value to give the variable appears on the
following lines. These lines are used verbatim; the character @samp{$} is
not treated specially and whitespace is not changed. The end of the value
is marked by a line containing just the word @code{endef}.
following lines. The end of the value is marked by a line containing just
the word @code{endef}. Aside from this difference in syntax, @code{define}
works just like @code{=}; it creates a recursively-expanded variable
(@pxref{Flavors}).
@example
define two-lines
@ -2024,13 +2079,10 @@ echo $(bar)
endef
@end example
Aside from the syntax, the only difference between @code{define} and
ordinary recursive variable assignments is that the text in a
@code{define} can be multiple lines. The value in an ordinary assignment
cannot contain a newline; but the newlines that separate the lines of the
value in a @code{define} become part of thew variable's value (except for
the final newline which is always present and is not considered part of
the value.)@refill
The value in an ordinary assignment cannot contain a newline; but the
newlines that separate the lines of the value in a @code{define} become
part of the variable's value (except for the final newline which precedes
the @code{endef} and is not considered part of the value).@refill
Thus the previous example is functionally equivalent to:
@ -2088,8 +2140,8 @@ A @dfn{conditional} causes part of a makefile to be obeyed or ignored
depending on the values of variables. Conditionals can compare the value
of one variable with another, or the value of a variable with a constant
string. Conditionals control what @code{make} actually ``sees'' in the
makefile, so they can @emph{not} be used to control commands at the time
of execution.@refill
makefile, so they @emph{cannot} be used to control shell commands at the
time of execution.@refill
@menu
* Example: Conditional Example. An annotated example.
@ -2345,7 +2397,7 @@ comma:= ,
space:= $(empty) $(empty)
foo:= a b c
bar:= $(subst $(space),$(comma),$(foo))
@r{# bar is now `a,b,c'.}
# @r{bar is now `a,b,c'.}
@end example
@noindent
@ -2356,8 +2408,8 @@ the value of @code{foo}, and substitutes the result.
@section Functions for String Substitution and Analysis
Here are some functions that operate on substrings of a string:
@code{subst}, @code{patsubst}, @code{findstring}, @code{filter}
and @code{filter-out}.
@code{subst}, @code{patsubst}, @code{strip}, @code{findstring},
@code{filter} and @code{filter-out}.
@table @code
@item $(subst @var{from},@var{to},@var{text})
@ -2374,12 +2426,21 @@ substitutes the string @samp{fEEt on the strEEt}.
@item $(patsubst @var{pattern},@var{replacement},@var{text})
@findex patsubst
Finds whitespace-separated words in @var{text} that match @var{pattern}
and replaces them with @var{replacement}. @var{pattern} may contain a
@samp{%} which acts as a wildcard, matching any number of any characters
within a word. If @var{replacement} also contains a @samp{%}, the @samp{%}
is replaced by the text that matched it in the pattern.
Whitespace between words is folded into single space characters.
Finds whitespace-separated words in @var{text} that match
@var{pattern} and replaces them with @var{replacement}. Here
@var{pattern} may contain a @samp{%} which acts as a wildcard,
matching any number of any characters within a word. If
@var{replacement} also contains a @samp{%}, the @samp{%} is replaced
by the text that matched the @samp{%} in @var{pattern}.
Whitespace between words is folded into single space characters;
leading and trailing whitespace is discarded.
@item $(strip @var{string})
@findex strip
Removes leading and trailing whitespace from @var{string} and replaces
each internal sequence of one or more whitespace characters with a
single space.
@item $(findstring @var{find},@var{in})
@findex findstring
@ -2443,14 +2504,10 @@ CFLAGS:= $(CFLAGS) $(addprefix -I,$(subst :, ,$(VPATH)))
The effect is to append the text @samp{-Isrc -I../headers} to the
previously given value of @code{CFLAGS}.
@findex strip
Another function, @code{strip}, simply removes leading and trailing
whitespace from its argument and replaces each internal sequence of one
or more whitespace characters with a single space. This function can be
very useful when used in conjunction with conditionals. When comparing
something with the null string @samp{""} using @code{ifeq} or @code{ifneq},
you usually want a string of just whitespace to match the null string.
Thus,
The function @code{strip} can be very useful when used in conjunction
with conditionals. When comparing something with the null string
@samp{""} using @code{ifeq} or @code{ifneq}, you usually want a string
of just whitespace to match the null string. Thus,
@example
.PHONY: all
@ -2462,9 +2519,9 @@ endif
@end example
@noindent
would probably not have the desired results, while replacing
might fail to have the desired results. Replacing
@samp{"$(needs_made)"} with @samp{"$(strip $(needs_made))"} in the
@code{ifneq} directive would.@refill
@code{ifneq} directive would make it more reliable.@refill
@node Filename Functions,, Text Functions, Functions
@section Functions for File Names
@ -2581,8 +2638,11 @@ from each argument) concatenated form the first word of the result, the
two second words form the second word of the result, and so on. So the
@var{n}th word of the result comes from the @var{n}th word of each
argument. If one argument has more words that the other, the extra
words are copied unchanged into the result. Whitespace between the words
in the lists is not preserved; it is replaced with a single space.
words are copied unchanged into the result.
Whitespace between the words in the lists is not preserved; it is
replaced with a single space.
This function can reverse the effect of the @code{dir} and @code{notdir}
functions, after other processing has been done on the separated lists
of directories and files.@refill
@ -2815,9 +2875,9 @@ invocation of @code{make}.
If you are not at all interested in what @code{make} @emph{would} do,
but rather in some other information about @code{make}, there are two
are options: the command line @code{make -p -f /dev/null} will print the
options: the command line @samp{make -p -f /dev/null} will print the
information in @code{make}'s database of variables, rules, directories
and files and @code{make -v -f /dev/null} will print information about
and files and @samp{make -v -f /dev/null} will print information about
what version of GNU @code{make} you are using. @xref{Options}.@refill
@node Overriding, Testing, Instead of Execution, Running
@ -2971,7 +3031,7 @@ Print the data base (rules and variable values) that results from
reading the makefiles; then execute as usual or as otherwise
specified. This also prints the version information given by
the @samp{-v} switch (see below). To print the data base without
trying to remake any files, use @code{make -p -f /dev/null}.
trying to remake any files, use @samp{make -p -f /dev/null}.
@item -q
``Question mode''. Do not run any commands, or print anything; just
@ -3003,12 +3063,13 @@ future invocations of @code{make}) that the commands were done.
Print the version of the @code{make} program plus a copyright,
list of authors and notice of (non)warranty (short).
After this information is printed, processing continues normally.
To get just the version information, use @code{make -v -f /dev/null}.
To get the version information without doing anything else,
use @samp{make -v -f /dev/null}.
@item -w
Print a message containing the working directory both before and after
executing the makefile; this is useful for tracking down errors from builds
of large directory trees. @xref{Recursion}.
executing the makefile; this is useful for tracking down errors from
builds of large directory trees. @xref{Recursion}.
@end table
@node Implicit, Archives, Running, Top
@ -3566,7 +3627,6 @@ The stem with which an implicit rule matches (@pxref{Pattern Match}).
If the target is @file{dir/a.foo.b} and the target pattern is
@file{a.%.b} then the stem is @file{dir/foo}. The stem is useful for
constructing names of related files.@refill
of @code{make}.
@end table
@samp{$?} is useful even in explicit rules when you wish to operate on only
@ -4041,8 +4101,8 @@ files into the archive, as described in the preceding section.
@node Missing, Concept Index, Archives, Top
The variable @code{MAKELEVEL} which keeps track of the current level
of @code{make} recursion. @xref{Recursion}.
The @code{make} programs in various other systems support two features that
are not implemented in GNU @code{make}.
The @code{make} programs in various other systems support three features
@item
Static pattern rules. @xref{Static Pattern}.
@item
@ -4065,6 +4125,14 @@ of archive file @var{file}. The member is chosen, not by name, but by
being an object file which defines the linker symbol @var{entry}.@refill
This feature was not put into GNU @code{make} because of the
nonmodularity of putting knowledge into @code{make} of the internal
format of archive file symbol directories. @xref{Archive Symbols}.
@item
Suffixes (used in suffix rules) that end with the character @samp{~}
have a special meaning; they refer to the SCCS file that corresponds
to the file one would get without the @samp{~}. For example, the
suffix rule @samp{.c~.o} would make the file @file{@var{n}.o} file from
@noindent
can be replaced with the GNU @code{make} static pattern rule: