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Added description of usage of the getPosition() option on cl::opt and

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cl::list.

llvm-svn: 15726
This commit is contained in:
Reid Spencer 2004-08-13 20:19:14 +00:00
parent 45d12b6601
commit 16cefa6880
1 changed files with 59 additions and 1 deletions
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docs/CommandLine.html
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@ -30,6 +30,8 @@
<li><a href="#positional">Positional Arguments</a>
<ul>
<li><a href="#--">Specifying positional options with hyphens</a></li>
<li><a href="#getPosition">Determining absolute position with
getPosition</a></li>
<li><a href="#cl::ConsumeAfter">The <tt>cl::ConsumeAfter</tt>
modifier</a></li>
</ul></li>
@ -780,7 +782,7 @@ OPTIONS:
<p>Positional arguments are sorted by their order of construction. This means
that command line options will be ordered according to how they are listed in a
.cpp file, but will not have an ordering defined if they positional arguments
.cpp file, but will not have an ordering defined if the positional arguments
are defined in multiple .cpp files. The fix for this problem is simply to
define all of your positional arguments in one .cpp file.</p>
@ -824,6 +826,62 @@ can use it like this:</p>
</div>
<!-- _______________________________________________________________________ -->
<div class="doc_subsubsection">
<a name="getPosition">Determining absolute position with getPosition()</a>
</div>
<div class="doc_text">
<p>Sometimes an option can affect or modify the meaning of another option. For
example, consider <tt>gcc</tt>'s <tt>-x LANG</tt> option. This tells
<tt>gcc</tt> to ignore the suffix of subsequent positional arguments and force
the file to be interpreted as if it contained source code in language
<tt>LANG</tt>. In order to handle this properly , you need to know the
absolute position of each argument, especially those in lists, so their
interaction(s) can be applied correctly. This is also useful for options like
<tt>-llibname</tt> which is actually a positional argument that starts with
a dash.</p>
<p>So, generally, the problem is that you have two <tt>cl::list</tt> variables
that interact in some way. To ensure the correct interaction, you can use the
<tt>cl::list::getPosition(optnum)</tt> method. This method returns the
absolute position (as found on the command line) of the <tt>optnum</tt>
item in the <tt>cl::list</tt>.</p>
<p>The idiom for usage is like this:<pre><tt>
static cl::list&lt;std::string&gt; Files(cl::Positional, cl::OneOrMore);
static cl::listlt;std::string&gt; Libraries("l", cl::ZeroOrMore);
int main(int argc, char**argv) {
// ...
std::vector&lt;std::string&gt;::iterator fileIt = Files.begin();
std::vector&lt;std::string&gt;::iterator libIt = Libraries.begin();
unsigned libPos = 0, filePos = 0;
while ( 1 ) {
if ( libIt != Libraries.end() )
libPos = Libraries.getPosition( libIt - Libraries.begin() );
else
libPos = 0;
if ( fileIt != Files.end() )
filePos = Files.getPosition( fileIt - Files.begin() );
else
filePos = 0;
if ( filePos != 0 &amp;&amp; (libPos == 0 || filePos &lt; libPos) ) {
// Source File Is next
++fileIt;
}
else if ( libPos != 0 &amp;&amp; (filePos == 0 || libPos &lt; filePos) ) {
// Library is next
++libIt;
}
else
break; // we're done with the list
}
}</tt></pre></p>
<p>Note that, for compatibility reasons, the <tt>cl::opt</tt> also supports an
<tt>unsigned getPosition()</tt> option that will provide the absolute position
of that option. You can apply the same approach as above with a
<tt>cl::opt</tt> and a <tt>cl::list</tt> option as you can with two lists.</p>
</div>
<!-- _______________________________________________________________________ -->
<div class="doc_subsubsection">
<a name="cl::ConsumeAfter">The <tt>cl::ConsumeAfter</tt> modifier</a>