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| <div class="section" id="cmp0054"> |
| <span id="policy:CMP0054"></span><h1>CMP0054<a class="headerlink" href="#cmp0054" title="Permalink to this headline">ΒΆ</a></h1> |
| <p>Only interpret <span class="target" id="index-0-command:if"></span><a class="reference internal" href="../command/if.html#command:if" title="if"><code class="xref cmake cmake-command docutils literal"><span class="pre">if()</span></code></a> arguments as variables or keywords when unquoted.</p> |
| <p>CMake 3.1 and above no longer implicitly dereference variables or |
| interpret keywords in an <span class="target" id="index-1-command:if"></span><a class="reference internal" href="../command/if.html#command:if" title="if"><code class="xref cmake cmake-command docutils literal"><span class="pre">if()</span></code></a> command argument when |
| it is a <a class="reference internal" href="../manual/cmake-language.7.html#quoted-argument"><span class="std std-ref">Quoted Argument</span></a> or a <a class="reference internal" href="../manual/cmake-language.7.html#bracket-argument"><span class="std std-ref">Bracket Argument</span></a>.</p> |
| <p>The <code class="docutils literal"><span class="pre">OLD</span></code> behavior for this policy is to dereference variables and |
| interpret keywords even if they are quoted or bracketed. |
| The <code class="docutils literal"><span class="pre">NEW</span></code> behavior is to not dereference variables or interpret keywords |
| that have been quoted or bracketed.</p> |
| <p>Given the following partial example:</p> |
| <div class="highlight-default"><div class="highlight"><pre><span></span><span class="nb">set</span><span class="p">(</span><span class="n">A</span> <span class="n">E</span><span class="p">)</span> |
| <span class="nb">set</span><span class="p">(</span><span class="n">E</span> <span class="s2">""</span><span class="p">)</span> |
| |
| <span class="k">if</span><span class="p">(</span><span class="s2">"$</span><span class="si">{A}</span><span class="s2">"</span> <span class="n">STREQUAL</span> <span class="s2">""</span><span class="p">)</span> |
| <span class="n">message</span><span class="p">(</span><span class="s2">"Result is TRUE before CMake 3.1 or when CMP0054 is OLD"</span><span class="p">)</span> |
| <span class="k">else</span><span class="p">()</span> |
| <span class="n">message</span><span class="p">(</span><span class="s2">"Result is FALSE in CMake 3.1 and above if CMP0054 is NEW"</span><span class="p">)</span> |
| <span class="n">endif</span><span class="p">()</span> |
| </pre></div> |
| </div> |
| <p>After explicit expansion of variables this gives:</p> |
| <div class="highlight-default"><div class="highlight"><pre><span></span><span class="k">if</span><span class="p">(</span><span class="s2">"E"</span> <span class="n">STREQUAL</span> <span class="s2">""</span><span class="p">)</span> |
| </pre></div> |
| </div> |
| <p>With the policy set to <code class="docutils literal"><span class="pre">OLD</span></code> implicit expansion reduces this semantically to:</p> |
| <div class="highlight-default"><div class="highlight"><pre><span></span><span class="k">if</span><span class="p">(</span><span class="s2">""</span> <span class="n">STREQUAL</span> <span class="s2">""</span><span class="p">)</span> |
| </pre></div> |
| </div> |
| <p>With the policy set to <code class="docutils literal"><span class="pre">NEW</span></code> the quoted arguments will not be |
| further dereferenced:</p> |
| <div class="highlight-default"><div class="highlight"><pre><span></span><span class="k">if</span><span class="p">(</span><span class="s2">"E"</span> <span class="n">STREQUAL</span> <span class="s2">""</span><span class="p">)</span> |
| </pre></div> |
| </div> |
| <p>This policy was introduced in CMake version 3.1. |
| CMake version 3.8.2 warns when the policy is not set and uses |
| <code class="docutils literal"><span class="pre">OLD</span></code> behavior. Use the <span class="target" id="index-0-command:cmake_policy"></span><a class="reference internal" href="../command/cmake_policy.html#command:cmake_policy" title="cmake_policy"><code class="xref cmake cmake-command docutils literal"><span class="pre">cmake_policy()</span></code></a> command to set |
| it to <code class="docutils literal"><span class="pre">OLD</span></code> or <code class="docutils literal"><span class="pre">NEW</span></code> explicitly.</p> |
| <div class="admonition note"> |
| <p class="first admonition-title">Note</p> |
| <p class="last">The <code class="docutils literal"><span class="pre">OLD</span></code> behavior of a policy is |
| <span class="target" id="index-0-manual:cmake-policies(7)"></span><a class="reference internal" href="../manual/cmake-policies.7.html#manual:cmake-policies(7)" title="cmake-policies(7)"><code class="xref cmake cmake-manual docutils literal"><span class="pre">deprecated</span> <span class="pre">by</span> <span class="pre">definition</span></code></a> |
| and may be removed in a future version of CMake.</p> |
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