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<title>Issue 284: unportable example in 20.3.7, p6</title>
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<p><em>This page is a snapshot from the LWG issues list, see the <a href="lwg-active.html">Library Active Issues List</a> for more information and the meaning of <a href="lwg-active.html#CD1">CD1</a> status.</em></p>
<h3 id="284"><a href="lwg-defects.html#284">284</a>. unportable example in 20.3.7, p6</h3>
<p><b>Section:</b> 22.10.8 <a href="https://wg21.link/comparisons">[comparisons]</a> <b>Status:</b> <a href="lwg-active.html#CD1">CD1</a>
 <b>Submitter:</b> Martin Sebor <b>Opened:</b> 2000-12-26 <b>Last modified:</b> 2016-01-28</p>
<p><b>Priority: </b>Not Prioritized
</p>
<p><b>View other</b> <a href="lwg-index-open.html#comparisons">active issues</a> in [comparisons].</p>
<p><b>View all other</b> <a href="lwg-index.html#comparisons">issues</a> in [comparisons].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#CD1">CD1</a> status.</p>
<p><b>Discussion:</b></p>
<p>The example in 22.10.8 <a href="https://wg21.link/comparisons">[comparisons]</a>, p6 shows how to use the C
library function <code>strcmp()</code> with the function pointer adapter
<code>ptr_fun()</code>. But since it's unspecified whether the C library
functions have <code>extern &quot;C&quot;</code> or <code>extern
&quot;C++&quot;</code> linkage [16.4.3.3 <a href="https://wg21.link/using.linkage">[using.linkage]</a>], and since
function pointers with different the language linkage specifications
(9.12 <a href="https://wg21.link/dcl.link">[dcl.link]</a>) are incompatible, whether this example is
well-formed is unspecified.
</p>


<p id="res-284"><b>Proposed resolution:</b></p>
<p>Change 22.10.8 <a href="https://wg21.link/comparisons">[comparisons]</a> paragraph 6 from:</p>
<blockquote>
  <p>[<i>Example:</i></p>
  <pre>
    replace_if(v.begin(), v.end(), not1(bind2nd(ptr_fun(strcmp), "C")), "C++");
  </pre>
  <p>replaces each <code>C</code> with <code>C++</code> in sequence <code>v</code>.</p>
</blockquote>


<p>to:</p>
<blockquote>
  <p>[<i>Example:</i></p>
  <pre>
    int compare(const char*, const char*);
    replace_if(v.begin(), v.end(),
               not1(bind2nd(ptr_fun(compare), "abc")), "def");
  </pre>
  <p>replaces each <code>abc</code> with <code>def</code> in sequence <code>v</code>.</p>
</blockquote>

<p>Also, remove footnote 215 in that same paragraph.</p>

<p><i>[Copenhagen: Minor change in the proposed resolution.  Since this
issue deals in part with C and C++ linkage, it was believed to be too
confusing for the strings in the example to be "C" and "C++".
]</i></p>


<p><i>[Redmond: More minor changes.  Got rid of the footnote (which
seems to make a sweeping normative requirement, even though footnotes
aren't normative), and changed the sentence after the footnote so that
it corresponds to the new code fragment.]</i></p>






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