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| <span id="policy:CMP0053"></span><h1>CMP0053<a class="headerlink" href="#cmp0053" title="Permalink to this headline">ΒΆ</a></h1> |
| <p>Simplify variable reference and escape sequence evaluation.</p> |
| <p>CMake 3.1 introduced a much faster implementation of evaluation of the |
| <a class="reference internal" href="../manual/cmake-language.7.html#variable-references"><span class="std std-ref">Variable References</span></a> and <a class="reference internal" href="../manual/cmake-language.7.html#escape-sequences"><span class="std std-ref">Escape Sequences</span></a> documented in the |
| <span class="target" id="index-0-manual:cmake-language(7)"></span><a class="reference internal" href="../manual/cmake-language.7.html#manual:cmake-language(7)" title="cmake-language(7)"><code class="xref cmake cmake-manual docutils literal"><span class="pre">cmake-language(7)</span></code></a> manual. While the behavior is identical |
| to the legacy implementation in most cases, some corner cases were |
| cleaned up to simplify the behavior. Specifically:</p> |
| <ul> |
| <li><p class="first">Expansion of <code class="docutils literal"><span class="pre">@VAR@</span></code> reference syntax defined by the |
| <span class="target" id="index-0-command:configure_file"></span><a class="reference internal" href="../command/configure_file.html#command:configure_file" title="configure_file"><code class="xref cmake cmake-command docutils literal"><span class="pre">configure_file()</span></code></a> and <span class="target" id="index-0-command:string"></span><a class="reference internal" href="../command/string.html#command:string" title="string"><code class="xref cmake cmake-command docutils literal"><span class="pre">string(CONFIGURE)</span></code></a> |
| commands is no longer performed in other contexts.</p> |
| </li> |
| <li><p class="first">Literal <code class="docutils literal"><span class="pre">${VAR}</span></code> reference syntax may contain only |
| alphanumeric characters (<code class="docutils literal"><span class="pre">A-Z</span></code>, <code class="docutils literal"><span class="pre">a-z</span></code>, <code class="docutils literal"><span class="pre">0-9</span></code>) and |
| the characters <code class="docutils literal"><span class="pre">_</span></code>, <code class="docutils literal"><span class="pre">.</span></code>, <code class="docutils literal"><span class="pre">/</span></code>, <code class="docutils literal"><span class="pre">-</span></code>, and <code class="docutils literal"><span class="pre">+</span></code>. |
| Variables with other characters in their name may still |
| be referenced indirectly, e.g.</p> |
| <div class="highlight-cmake"><div class="highlight"><pre><span></span><span class="nb">set</span><span class="p">(</span><span class="s">varname</span> <span class="s2">"otherwise & disallowed $ characters"</span><span class="p">)</span> |
| <span class="nb">message</span><span class="p">(</span><span class="s2">"${${varname}}"</span><span class="p">)</span> |
| </pre></div> |
| </div> |
| </li> |
| <li><p class="first">The setting of policy <span class="target" id="index-0-policy:CMP0010"></span><a class="reference internal" href="CMP0010.html#policy:CMP0010" title="CMP0010"><code class="xref cmake cmake-policy docutils literal"><span class="pre">CMP0010</span></code></a> is not considered, |
| so improper variable reference syntax is always an error.</p> |
| </li> |
| <li><p class="first">More characters are allowed to be escaped in variable names. |
| Previously, only <code class="docutils literal"><span class="pre">()#"</span> <span class="pre">\@^</span></code> were valid characters to |
| escape. Now any non-alphanumeric, non-semicolon, non-NUL |
| character may be escaped following the <code class="docutils literal"><span class="pre">escape_identity</span></code> |
| production in the <a class="reference internal" href="../manual/cmake-language.7.html#escape-sequences"><span class="std std-ref">Escape Sequences</span></a> section of the |
| <span class="target" id="index-1-manual:cmake-language(7)"></span><a class="reference internal" href="../manual/cmake-language.7.html#manual:cmake-language(7)" title="cmake-language(7)"><code class="xref cmake cmake-manual docutils literal"><span class="pre">cmake-language(7)</span></code></a> manual.</p> |
| </li> |
| </ul> |
| <p>The <code class="docutils literal"><span class="pre">OLD</span></code> behavior for this policy is to honor the legacy behavior for |
| variable references and escape sequences. The <code class="docutils literal"><span class="pre">NEW</span></code> behavior is to |
| use the simpler variable expansion and escape sequence evaluation rules.</p> |
| <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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