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diff --git a/doc/html/bbv2/faq.html b/doc/html/bbv2/faq.html new file mode 100644 index 0000000000..acb25c5188 --- /dev/null +++ b/doc/html/bbv2/faq.html @@ -0,0 +1,149 @@ +<html> +<head> +<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> +<title>Chapter 27. Frequently Asked Questions</title> +<link rel="stylesheet" href="../boostbook.css" type="text/css"> +<meta name="generator" content="DocBook XSL Stylesheets V1.68.1"> +<style type="text/css"> +body { background-image: url('http://docbook.sourceforge.net/release/images/draft.png'); + background-repeat: no-repeat; + background-position: top left; + /* The following properties make the watermark "fixed" on the page. */ + /* I think that's just a bit too distracting for the reader... */ + /* background-attachment: fixed; */ + /* background-position: center center; */ + }</style> +<link rel="start" href="../index.html" title="The Boost C++ Libraries"> +<link rel="up" href="../bbv2.html" title="Part III. Boost.Build v2 User Manual"> +<link rel="prev" href="reference/generators.html" title="Generators"> +<link rel="next" href="faq/envar.html" title=" + Accessing environment variables + "> +</head> +<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> +<table cellpadding="2" width="100%"> +<td valign="top"><img alt="boost.png (6897 bytes)" width="277" height="86" src="../../../boost.png"></td> +<td align="center"><a href="../../../index.htm">Home</a></td> +<td align="center"><a href="../../../libs/libraries.htm">Libraries</a></td> +<td align="center"><a href="../../../people/people.htm">People</a></td> +<td align="center"><a href="../../../more/faq.htm">FAQ</a></td> +<td align="center"><a href="../../../more/index.htm">More</a></td> +</table> +<hr> +<div class="spirit-nav"> +<a accesskey="p" href="reference/generators.html"><img src="../images/prev.png" alt="Prev"></a><a accesskey="u" href="../bbv2.html"><img src="../images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../images/home.png" alt="Home"></a><a accesskey="n" href="faq/envar.html"><img src="../images/next.png" alt="Next"></a> +</div> +<div class="chapter" lang="en"> +<div class="titlepage"><div><div><h2 class="title"> +<a name="bbv2.faq"></a>Chapter 27. Frequently Asked Questions</h2></div></div></div> +<div class="toc"> +<p><b>Table of Contents</b></p> +<dl> +<dt><span class="section"><a href="faq.html#id1708877"> + I'm getting "Duplicate name of actual target" error. What + does it mean? + </a></span></dt> +<dt><span class="section"><a href="faq/envar.html"> + Accessing environment variables + </a></span></dt> +<dt><span class="section"><a href="faq/s03.html"> + How to control properties order? + </a></span></dt> +<dt><span class="section"><a href="faq/s04.html"> + How to control the library order on Unix? + </a></span></dt> +<dt><span class="section"><a href="faq/external.html">Can I get output of external program as a variable in a Jamfile? + </a></span></dt> +<dt><span class="section"><a href="faq/s06.html">How to get the project-root location? + </a></span></dt> +<dt><span class="section"><a href="faq/s07.html">How to change compilation flags for one file? + </a></span></dt> +<dt><span class="section"><a href="faq/dll-path.html">Why are the <code class="computeroutput">dll-path</code> and + <code class="computeroutput">hardcode-dll-paths</code> properties useful? + </a></span></dt> +<dt><span class="section"><a href="recipies/site-config.html">Targets in site-config.jam</a></span></dt> +</dl> +</div> +<div class="section" lang="en"> +<div class="titlepage"><div><div><h2 class="title" style="clear: both"> +<a name="id1708877"></a> + I'm getting "Duplicate name of actual target" error. What + does it mean? + </h2></div></div></div> +<p> + The most likely case is that you're trying to + compile the same file twice, with almost the same, + but differing properties. For example: + +</p> +<pre class="programlisting"> +exe a : a.cpp : <include>/usr/local/include ; +exe b : a.cpp ; +</pre> +<p> + The above snippet requires two different compilations + of 'a.cpp', which differ only in 'include' property. + Since the 'include' property is free, Boost.Build + can't generate two objects files into different directories. + On the other hand, it's dangerous to compile the file only + once -- maybe you really want to compile with different + includes. + </p> +<p> + To solve this issue, you need to decide if file should + be compiled once or twice.</p> +<div class="orderedlist"><ol type="1"> +<li> +<p>Two compile file only once, make sure that properties + are the same: + +</p> +<pre class="programlisting"> +exe a : a.cpp : <include>/usr/local/include ; +exe b : a.cpp : <include>/usr/local/include ; +</pre> +</li> +<li> +<p> + If changing the properties is not desirable, for example + if 'a' and 'b' target have other sources which need + specific properties, separate 'a.cpp' into it's own target: + +</p> +<pre class="programlisting"> +obj a_obj : a.cpp : <include>/usr/local/include ; +exe a : a_obj ; +</pre> +</li> +<li> +<p> + To compile file twice, you can make the object file local + to the main target: + +</p> +<pre class="programlisting"> + exe a : [ obj a_obj : a.cpp ] : <include>/usr/local/include ; + exe b : [ obj a_obj : a.cpp ] ; +</pre> +</li> +</ol></div> +<p> + A good question is why Boost.Build can't use some of the above + approaches automatically. The problem is that such magic would + require additional implementation complexities and would only + help in half of the cases, while in other half we'd be silently + doing the wrong thing. It's simpler and safe to ask user to + clarify his intention in such cases. + </p> +</div> +</div> +<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> +<td align="left"></td> +<td align="right"><small></small></td> +</tr></table> +<hr> +<div class="spirit-nav"> +<a accesskey="p" href="reference/generators.html"><img src="../images/prev.png" alt="Prev"></a><a accesskey="u" href="../bbv2.html"><img src="../images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../images/home.png" alt="Home"></a><a accesskey="n" href="faq/envar.html"><img src="../images/next.png" alt="Next"></a> +</div> +</body> +</html> |