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- Improve text on RUN_DEPENDS

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PR:		docs/149480
Submitted by:	sahil
This commit is contained in:
Gabor Pali 2010-08-11 19:37:15 +00:00
parent 9635d96d04
commit 0a9be94096
Notes: svn2git 2020-12-08 03:00:23 +00:00 
svn path=/head/; revision=36227
1 changed files with 16 additions and 21 deletions
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37
en_US.ISO8859-1/books/porters-handbook/book.sgml
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@ -3283,33 +3283,28 @@ ALWAYS_KEEP_DISTFILES= yes
part can be omitted if it is the same as
<makevar>DEPENDS_TARGET</makevar>.</para>
<para>Quite common situation is when
<para>A quite common situation is when
<makevar>RUN_DEPENDS</makevar> is literally the same as
<makevar>BUILD_DEPENDS</makevar>, especially if ported
software is written in a scripted language or if it requires
the same run-time environment used to build it. In this
case, it is very tempting, and indeed natural to directly
assign one to another:</para>
the same build and run-time environment. In this
case, it is both tempting and intuitive to directly
assign one to the other:</para>
<programlisting>RUN_DEPENDS= ${BUILD_DEPENDS}</programlisting>
<para>However, doing so can and often will result in
run-time dependencies be polluted by superfluous entries, not
present in original port's <makevar>BUILD_DEPENDS</makevar>.
It happens due to the fact that &man.make.1 is being lazy
when it evaluates assignments like these. Most probably
additional dependencies will be pulled by
<filename>ports/Mk/bsd.*.mk</filename> when processing
<makevar>USE_<replaceable>*</replaceable></makevar>
variables, which most ports contain. For example, such
direct assignment along with
<literal>USE_GMAKE=yes</literal> will bring
<application>gmake</application> into
<makevar>RUN_DEPENDS</makevar>, despite that it was not
included explicitly in <makevar>BUILD_DEPENDS</makevar>. To
prevent this from happening, immediate expansion assignment
should be used, i.e. expand the value before assigning it
to the variable:</para>
<para>However, such assignment can pollute run-time dependencies
with entries not defined in the port's original <makevar>BUILD_DEPENDS</makevar>.
This happens because of &man.make.1;'s lazy evaluation of variable
assignment. Consider a <filename>Makefile</filename> with
<makevar>USE_<replaceable>*</replaceable></makevar> variables, which
are processed by <filename>ports/Mk/bsd.*.mk</filename> to augment
initial build dependencies. For example, <literal>USE_GMAKE=yes</literal>
adds <filename role="package">devel/gmake</filename> to
<makevar>BUILD_DEPENDS</makevar>. To prevent such additional dependencies
from polluting <makevar>RUN_DEPENDS</makevar>, take care to assign
with expansion, i.e. expand the value before assigning it to the
variable:</para>
<programlisting>RUN_DEPENDS:= ${BUILD_DEPENDS}</programlisting>
</sect2>