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Formerly make.texinfo.~109~

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Roland McGrath 1993-07-16 22:14:09 +00:00
parent cace096aba
commit d24f1f2330
1 changed files with 14 additions and 9 deletions
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23
make.texinfo
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@ -4174,16 +4174,20 @@ it is this unexpanded text to which @code{make} appends the new text you
specify. specify.
@example @example
@group
variable = value variable = value
variable += more variable += more
@end group
@end example @end example
@noindent @noindent
is roughly equivalent to: is roughly equivalent to:
@example @example
@group
temp = value temp = value
variable = $(temp) more variable = $(temp) more
@end group
@end example @end example
@noindent @noindent
@ -4213,15 +4217,16 @@ CFLAGS := $(CFLAGS) -pg # enable profiling
@end example @end example
@noindent @noindent
This is close, but not quite what we want. Using @samp{:=} redefines This is pretty close, but not quite what we want. Using @samp{:=}
@code{CFLAGS} as a simply-expanded variable; this means @code{make} expands redefines @code{CFLAGS} as a simply-expanded variable; this means
the text @w{@samp{$(CFLAGS) -pg}} before setting the variable. If @code{make} expands the text @w{@samp{$(CFLAGS) -pg}} before setting the
@code{includes} is not yet defined, we get @w{@samp{ -O -pg}}, and a later variable. If @code{includes} is not yet defined, we get @w{@samp{ -O
definition of @code{includes} will have no effect. Conversely, by using -pg}}, and a later definition of @code{includes} will have no effect.
@samp{+=} we set @code{CFLAGS} to the @emph{unexpanded} value Conversely, by using @samp{+=} we set @code{CFLAGS} to the
@w{@samp{$(includes) -O -pg}}. Thus we preserve the reference to @emph{unexpanded} value @w{@samp{$(includes) -O -pg}}. Thus we preserve
@code{includes}, so if that variable gets defined at any later point, a the reference to @code{includes}, so if that variable gets defined at
reference like @samp{$(CFLAGS)} still uses its value. any later point, a reference like @samp{$(CFLAGS)} still uses its
value.
@node Override Directive, Defining, Appending, Using Variables @node Override Directive, Defining, Appending, Using Variables
@section The @code{override} Directive @section The @code{override} Directive