and issues the commands to recompile them.
@c !!set edition, date, version
-This is Edition 0.33 Beta, last updated 6 July 1992,
+This is Edition 0.33 Beta, last updated 16 July 1992,
of @cite{The GNU Make Manual}, for @code{make}, Version 3.63 Beta.
Copyright (C) 1988, 1989, 1990, 1991, 1992 Free Software Foundation, Inc.
@title GNU Make
@subtitle A Program for Directing Recompilation
@subtitle Edition 0.33 Beta, for @code{make} Version 3.63 Beta.
-@subtitle June 1992
+@subtitle July 1992
@author by Richard M. Stallman and Roland McGrath
@page
@vskip 0pt plus 1filll
recompile them.@refill
This is Edition 0.33 Beta of the @cite{GNU Make Manual},
-last updated 12 June 1992,
+last updated 16 July 1992
for @code{make} Version 3.63 Beta.@refill
This manual describes @code{make} and contains the following chapters:@refill
@end ifinfo
+@c !!! Edit descriptions.
@menu
* Copying:: GNU GENERAL PUBLIC LICENSE
* Overview:: Introducing @code{make}.
specified by the existing contents of @file{mfile}.
@node Overriding Makefiles, , Remaking Makefiles, Makefiles
-@section Overriding Part of One Makefile with Another Makefile
+@section Overriding Part of Another Makefile
@cindex overriding makefiles
Sometimes it is useful to have a makefile that is mostly just like
A phony target is one that is not really the name of a file. It is just a
name for some commands to be executed when you make an explicit request.
+There are two reasons to use a phony target: to avoid a conflict with
+file of the same name, and to improve performance.
If you write a rule whose commands will not create the target file, the
commands will be executed every time the target comes up for remaking.
probably no such file will ever exist. Therefore, the @code{rm} command
will be executed every time you say @samp{make clean}.
-@c !!!! want to mention that using .PHONY is a performance win because
-@c implicit rule serach is not done for phony targets --roland
-
@findex .PHONY
The phony target will cease to work if anything ever does create a file
named @file{clean} in this directory. Since it has no dependencies, the
Once this is done, @samp{make clean} will run the commands regardless of
whether there is a file named @file{clean}.
+Since @code{make} knows that phony targets do not name actual files
+that could be remade from other files, @code{make} skips the implicit
+rule search for phony targets (@pxref{Implicit}). This is why
+declaring a target phony is good for performance, even if you are not
+worried about the actual file existing.
+
Thus, you first write the line that states that @code{clean} is a
phony target, then you write the rule, like this:
this is not totally reliable; some makefiles set @code{CFLAGS} explicitly
and therefore are not affected by the value in the environment.)
-@c !!!! this is completely wrong --roland
-When @code{make} is invoked recursively, variables defined in the outer
-invocation are automatically passed to inner invocations through the
-environment (@pxref{Recursion, ,Recursive Use of @code{make}}). This is the main purpose of turning
-environment variables into @code{make} variables, and it requires no
-attention from you.@refill
+When @code{make} is invoked recursively, variables defined in the
+outer invocation can be passed to inner invocations through the
+environment (@pxref{Recursion, ,Recursive Use of @code{make}}). By
+default, only variables that came from the environment or the command
+line are passed to recursive invocations. You can use the
+@code{export} directive to pass other variables.
+@xref{Variables/Recursion, , Communicating Variables to a
+Sub-@code{make}}, for full details.
Other use of variables from the environment is not recommended. It is not
wise for makefiles to depend for their functioning on environment variables
The @code{endif} directive ends the conditional. Every conditional must
end with an @code{endif}. Unconditional makefile text follows.
-@c !!!! this is repeated below --roland
-Conditionals work at the textual level: the lines of the conditional are
-treated as part of the makefile, or ignored, according to the condition.
-This is why the larger syntactic units of the makefile, such as rules, may
-cross the beginning or the end of the conditional.
+As this example illustrates, conditionals work at the textual level:
+the lines of the conditional are treated as part of the makefile, or
+ignored, according to the condition. This is why the larger syntactic
+units of the makefile, such as rules, may cross the beginning or the
+end of the conditional.
When the variable @code{CC} has the value @samp{gcc}, the above example has
this effect:
line, and spaces or tabs at the end. A comment starting with @samp{#} may
appear at the end of the line.
-@c !!!! repeated above
-Conditionals work at the textual level. The lines of the
-@var{text-if-true} are read as part of the makefile if the condition is
-true; if the condition is false, those lines are ignored completely. It
-follows that syntactic units of the makefile, such as rules, may safely be
-split across the beginning or the end of the conditional.@refill
+Conditionals affect which lines of the makefile @code{make} uses. If
+the condition is true, @code{make} reads the lines of the
+@var{text-if-true} as part of the makefile; if the condition is false,
+@code{make} ignores those lines completely. It follows that syntactic
+units of the makefile, such as rules, may safely be split across the
+beginning or the end of the conditional.@refill
+
+@code{make} evaluates conditionals when it reads a makefile.
+Consequently, you cannot use automatic variables in the tests of
+conditionals because they are not defined until commands are run
+(@pxref{Automatic}).
To prevent intolerable confusion, it is not permitted to start a
conditional in one makefile and end it in another. However, you may
For example, given:
-@noindent @c !!!! will this do what I want? --roland
@example
@group
objects=main1.o foo.o main2.o bar.o
For example,
-@noindent @c !!!! ? --roland
@example
$(firstword foo bar)
@end example
@node Running, Implicit Rules, Functions, Top
@chapter How to Run @code{make}
-A makefile that says how to recompile a program can be used in more than
-one way. The simplest use is to recompile every file that is out of date.
-This is what @code{make} will do if run with no arguments.
-@c !!!! this is misleading --roland
+A makefile that says how to recompile a program can be used in more
+than one way. The simplest use is to recompile every file that is out
+of date. Usually, makefiles are written so that if you run
+@code{make} with no arguments, it does just that.
But you might want to update only some of the files; you might want to use
a different compiler or different compiler options; you might want just to
of the suffixes that are on the list you specify; rules whose suffixes
fail to be on the list are disabled.@refill
-@c !!!! do we want to document $(COMPILE.c) et al? --roland
-@c !!!! and $(TARGET_ARCH)?
-
@table @asis
@item Compiling C programs
@file{@var{n}.o} will be made automatically from @file{@var{n}.c} with
software movement.
@end table
+Usually, you want to change only the variables listed in the table
+above, which are documented in the following section.
+
+However, the commands in built-in implicit rules actually use
+variables such as @code{COMPILE.c}, @code{LINK.p}, and
+@code{PREPROCESS.S}, whose values contain the commands listed above.
+
+@code{make} follows the convention that the rule to compile a
+@file{.@var{x}} source file uses the variable @code{COMPILE.@var{x}}.
+Similarly, the rule to produce an executable from a @file{.@var{x}}
+file uses @code{LINK.@var{x}}; and the rule to preprocess a
+@file{.@var{x}} file uses @code{PREPROCESS.@var{x}}.
+
+Every rule that produces an object file uses the variable
+@code{OUTPUT_OPTION}. @code{make} defines this variable either to
+contain @samp{-o $@@}, or to be empty, depending on a compile-time
+option. You need the @samp{-o} option to ensure that the output goes
+into the right file when the source file is in a different directory,
+as when using @code{VPATH} (@pxref{Directory Search}). However,
+compilers on some systems do not accept a @samp{-o} switch for object
+files. If you use such a system, and use @code{VPATH}, some
+compilations will put their output in the wrong place.
+
@node Implicit Variables, Chained Rules, Catalogue of Rules, Implicit Rules
@section Variables Used by Implicit Rules
@cindex flags for compilers
@subsection Introduction to Pattern Rules
@cindex pattern rule
-@c !!!! this paragraph is a repeat of the first paragraph of prev node
-You define an implicit rule by writing a @dfn{pattern rule}. A pattern
-rule looks like an ordinary rule, except that its target contains the
-character @samp{%} (exactly one of them). The target is considered a
-pattern for matching file names; the @samp{%} can match any nonempty
-substring, while other characters match only themselves.
+A pattern rule contains the character @samp{%} (exactly one of them)
+in the target; otherwise, it looks exactly like an ordinary rule. The
+target is a pattern for matching file names; the @samp{%} matches any
+nonempty substring, while other characters match only themselves.
For example, @samp{%.c} as a pattern matches any file name that ends in
@samp{.c}. @samp{s.%.c} as a pattern matches any file name that starts
and doing such a thing simply does not fit the model.@refill
@end itemize
-@node Summary, Complex Makefile, Missing, Top
-@appendix Summary of Directives, Functions, and Special Variables
-@c !!!! this title is too long for the page
+@node Quick Reference, Complex Makefile, Missing, Top
+@appendix Quick Reference
This appendix summarizes the directives, text manipulation functions,
and special variables which GNU @code{make} understands.
# Copyright (C) 1991 Free Software Foundation, Inc.
@end group
-@c !!!! must we have all this copying info? --roland
@group
# This program is free software; you can redistribute
# it and/or modify it under the terms of the GNU
-# General Public License as published by the Free
-# Software Foundation; either version 2, or (at your
-# option) any later version.
-@end group
-
-# This program is distributed in the hope that it will
-# be useful, but WITHOUT ANY WARRANTY; without even
-# the implied warranty of MERCHANTABILITY or FITNESS
-# FOR A PARTICULAR PURPOSE.
-# See the GNU General Public License for more details.
-
-@group
-# You should have received a copy of the GNU General
-# Public License along with this program; if not,
-# write to the Free Software Foundation, Inc.,
-# 675 Mass Ave, Cambridge, MA 02139, USA.
+# General Public License @dots{}
+@dots{}
+@dots{}
@end group
SHELL = /bin/sh
projects / platform / upstream / make.git / commitdiff