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-rw-r--r--doc/make.texi77
1 files changed, 46 insertions, 31 deletions
diff --git a/doc/make.texi b/doc/make.texi
index 9b8faee..d723d2d 100644
--- a/doc/make.texi
+++ b/doc/make.texi
@@ -1399,6 +1399,7 @@ Variable definitions are parsed as follows:
@var{immediate} = @var{deferred}
@var{immediate} ?= @var{deferred}
@var{immediate} := @var{immediate}
+@var{immediate} ::= @var{immediate}
@var{immediate} += @var{deferred} or @var{immediate}
@var{immediate} != @var{immediate}
@@ -1418,6 +1419,10 @@ define @var{immediate} :=
@var{immediate}
endef
+define @var{immediate} ::=
+ @var{immediate}
+endef
+
define @var{immediate} +=
@var{deferred} or @var{immediate}
endef
@@ -1429,7 +1434,7 @@ endef
For the append operator, @samp{+=}, the right-hand side is considered
immediate if the variable was previously set as a simple variable
-(@samp{:=}), and deferred otherwise.
+(@samp{:=} or @samp{::=}), and deferred otherwise.
For the shell assignment operator, @samp{!=}, the right-hand side is
evaluated immediately and handed to the shell. The result is stored in the
@@ -4967,9 +4972,9 @@ all:;echo $(foo)
will echo @samp{Huh?}: @samp{$(foo)} expands to @samp{$(bar)} which
expands to @samp{$(ugh)} which finally expands to @samp{Huh?}.@refill
-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:
+This flavor of variable is the only sort supported by most other
+versions of @code{make}. It has its advantages and its disadvantages.
+An advantage (most would say) is that:
@example
CFLAGS = $(include_dirs) -O
@@ -5005,8 +5010,14 @@ variables, there is another flavor: simply expanded variables.
@cindex simply expanded variables
@cindex variables, simply expanded
@cindex :=
+@cindex ::=
@dfn{Simply expanded variables} are defined by lines using @samp{:=}
-(@pxref{Setting, ,Setting Variables}).
+or @samp{::=} (@pxref{Setting, ,Setting Variables}). Both forms are
+equivalent in GNU @code{make}; however only the @samp{::=} form is
+described by the POSIX standard (support for @samp{::=} was added to
+the POSIX standard in 2012, so older versions of @code{make} won't
+accept this form either).
+
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
@@ -5425,12 +5436,14 @@ Several variables have constant initial values.
@cindex variables, setting
@cindex =
@cindex :=
+@cindex ::=
@cindex ?=
@cindex !=
To set a variable from the makefile, write a line starting with the
-variable name followed by @samp{=} or @samp{:=}. Whatever follows the
-@samp{=} or @samp{:=} on the line becomes the value. For example,
+variable name followed by @samp{=} @samp{:=}, or @samp{::=}. Whatever
+follows the @samp{=}, @samp{:=}, or @samp{::=} on the line becomes the
+value. For example,
@example
objects = main.o foo.o bar.o utils.o
@@ -5440,10 +5453,11 @@ objects = main.o foo.o bar.o utils.o
defines a variable named @code{objects}. Whitespace around the variable
name and immediately after the @samp{=} is ignored.
-Variables defined with @samp{=} are @dfn{recursively expanded} variables.
-Variables defined with @samp{:=} are @dfn{simply expanded} variables; these
-definitions can contain variable references which will be expanded before
-the definition is made. @xref{Flavors, ,The Two Flavors of Variables}.
+Variables defined with @samp{=} are @dfn{recursively expanded}
+variables. Variables defined with @samp{:=} or @samp{::=} are
+@dfn{simply expanded} variables; these definitions can contain
+variable references which will be expanded before the definition is
+made. @xref{Flavors, ,The Two Flavors of Variables}.
The variable name may contain function and variable references, which
are expanded when the line is read to find the actual variable name to use.
@@ -5553,12 +5567,12 @@ explanation of the two flavors of variables.
When you add to a variable's value with @samp{+=}, @code{make} acts
essentially as if you had included the extra text in the initial
-definition of the variable. If you defined it first with @samp{:=},
-making it a simply-expanded variable, @samp{+=} adds to that
-simply-expanded definition, and expands the new text before appending it
-to the old value just as @samp{:=} does
-(see @ref{Setting, ,Setting Variables}, for a full explanation of @samp{:=}).
-In fact,
+definition of the variable. If you defined it first with @samp{:=} or
+@samp{::=}, making it a simply-expanded variable, @samp{+=} adds to
+that simply-expanded definition, and expands the new text before
+appending it to the old value just as @samp{:=} does (see
+@ref{Setting, ,Setting Variables}, for a full explanation of
+@samp{:=} or @samp{::=}). In fact,
@example
variable := value
@@ -5898,13 +5912,13 @@ Multiple @var{target} values create a target-specific variable value for
each member of the target list individually.
The @var{variable-assignment} can be any valid form of assignment;
-recursive (@samp{=}), simple (@samp{:=}), appending (@samp{+=}), or
-conditional (@samp{?=}). All variables that appear within the
-@var{variable-assignment} are evaluated within the context of the
-target: thus, any previously-defined target-specific variable values
-will be in effect. Note that this variable is actually distinct from
-any ``global'' value: the two variables do not have to have the same
-flavor (recursive vs.@: simple).
+recursive (@samp{=}), simple (@samp{:=} or @samp{::=}), appending
+(@samp{+=}), or conditional (@samp{?=}). All variables that appear
+within the @var{variable-assignment} are evaluated within the context
+of the target: thus, any previously-defined target-specific variable
+values will be in effect. Note that this variable is actually
+distinct from any ``global'' value: the two variables do not have to
+have the same flavor (recursive vs.@: simple).
Target-specific variables have the same priority as any other makefile
variable. Variables provided on the command line (and in the
@@ -8463,10 +8477,10 @@ makefile works by changing the variables.
When you override a variable with a command line argument, you can
define either a recursively-expanded variable or a simply-expanded
variable. The examples shown above make a recursively-expanded
-variable; to make a simply-expanded variable, write @samp{:=} instead
-of @samp{=}. But, unless you want to include a variable reference or
-function call in the @emph{value} that you specify, it makes no
-difference which kind of variable you create.
+variable; to make a simply-expanded variable, write @samp{:=} or
+@samp{::=} instead of @samp{=}. But, unless you want to include a
+variable reference or function call in the @emph{value} that you
+specify, it makes no difference which kind of variable you create.
There is one way that the makefile can change a variable that you have
overridden. This is to use the @code{override} directive, which is a line
@@ -11024,6 +11038,7 @@ Here is a summary of the directives GNU @code{make} recognizes:
@item define @var{variable}
@itemx define @var{variable} =
@itemx define @var{variable} :=
+@itemx define @var{variable} ::=
@itemx define @var{variable} +=
@itemx define @var{variable} ?=
@itemx endef
@@ -11479,9 +11494,9 @@ prerequisites, etc., one of them depended on @var{xxx} again.
@item Recursive variable `@var{xxx}' references itself (eventually). Stop.
This means you've defined a normal (recursive) @code{make} variable
@var{xxx} that, when it's expanded, will refer to itself (@var{xxx}).
-This is not allowed; either use simply-expanded variables (@code{:=}) or
-use the append operator (@code{+=}). @xref{Using Variables, ,How to Use
-Variables}.
+This is not allowed; either use simply-expanded variables (@samp{:=}
+or @samp{::=}) or use the append operator (@samp{+=}). @xref{Using
+Variables, ,How to Use Variables}.
@item Unterminated variable reference. Stop.
This means you forgot to provide the proper closing parenthesis