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| <div class="section" id="cmp0077"> |
| <span id="policy:CMP0077"></span><h1>CMP0077<a class="headerlink" href="#cmp0077" title="Permalink to this headline">ΒΆ</a></h1> |
| <div class="versionadded"> |
| <p><span class="versionmodified added">New in version 3.13.</span></p> |
| </div> |
| <p><span class="target" id="index-0-command:option"></span><a class="reference internal" href="../command/option.html#command:option" title="option"><code class="xref cmake cmake-command docutils literal notranslate"><span class="pre">option()</span></code></a> honors normal variables.</p> |
| <p>The <span class="target" id="index-1-command:option"></span><a class="reference internal" href="../command/option.html#command:option" title="option"><code class="xref cmake cmake-command docutils literal notranslate"><span class="pre">option()</span></code></a> command is typically used to create a cache entry |
| to allow users to set the option. However, there are cases in which a |
| normal (non-cached) variable of the same name as the option may be |
| defined by the project prior to calling the <span class="target" id="index-2-command:option"></span><a class="reference internal" href="../command/option.html#command:option" title="option"><code class="xref cmake cmake-command docutils literal notranslate"><span class="pre">option()</span></code></a> command. |
| For example, a project that embeds another project as a subdirectory |
| may want to hard-code options of the subproject to build the way it needs.</p> |
| <p>For historical reasons in CMake 3.12 and below the <span class="target" id="index-3-command:option"></span><a class="reference internal" href="../command/option.html#command:option" title="option"><code class="xref cmake cmake-command docutils literal notranslate"><span class="pre">option()</span></code></a> |
| command <em>removes</em> a normal (non-cached) variable of the same name when:</p> |
| <ul class="simple"> |
| <li><p>a cache entry of the specified name does not exist at all, or</p></li> |
| <li><p>a cache entry of the specified name exists but has not been given |
| a type (e.g. via <code class="docutils literal notranslate"><span class="pre">-D<name>=ON</span></code> on the command line).</p></li> |
| </ul> |
| <p>In both of these cases (typically on the first run in a new build tree), |
| the <span class="target" id="index-4-command:option"></span><a class="reference internal" href="../command/option.html#command:option" title="option"><code class="xref cmake cmake-command docutils literal notranslate"><span class="pre">option()</span></code></a> command gives the cache entry type <code class="docutils literal notranslate"><span class="pre">BOOL</span></code> and |
| removes any normal (non-cached) variable of the same name. In the |
| remaining case that the cache entry of the specified name already |
| exists and has a type (typically on later runs in a build tree), the |
| <span class="target" id="index-5-command:option"></span><a class="reference internal" href="../command/option.html#command:option" title="option"><code class="xref cmake cmake-command docutils literal notranslate"><span class="pre">option()</span></code></a> command changes nothing and any normal variable of |
| the same name remains set.</p> |
| <p>In CMake 3.13 and above the <span class="target" id="index-6-command:option"></span><a class="reference internal" href="../command/option.html#command:option" title="option"><code class="xref cmake cmake-command docutils literal notranslate"><span class="pre">option()</span></code></a> command prefers to |
| do nothing when a normal variable of the given name already exists. |
| It does not create or update a cache entry or remove the normal variable. |
| The new behavior is consistent between the first and later runs in a |
| build tree. This policy provides compatibility with projects that have |
| not been updated to expect the new behavior.</p> |
| <p>When the <span class="target" id="index-7-command:option"></span><a class="reference internal" href="../command/option.html#command:option" title="option"><code class="xref cmake cmake-command docutils literal notranslate"><span class="pre">option()</span></code></a> command sees a normal variable of the given |
| name:</p> |
| <ul class="simple"> |
| <li><p>The <code class="docutils literal notranslate"><span class="pre">OLD</span></code> behavior for this policy is to proceed even when a normal |
| variable of the same name exists. If the cache entry does not already |
| exist and have a type then it is created and/or given a type and the |
| normal variable is removed.</p></li> |
| <li><p>The <code class="docutils literal notranslate"><span class="pre">NEW</span></code> behavior for this policy is to do nothing when a normal |
| variable of the same name exists. The normal variable is not removed. |
| The cache entry is not created or updated and is ignored if it exists.</p></li> |
| </ul> |
| <p>See <span class="target" id="index-0-policy:CMP0126"></span><a class="reference internal" href="CMP0126.html#policy:CMP0126" title="CMP0126"><code class="xref cmake cmake-policy docutils literal notranslate"><span class="pre">CMP0126</span></code></a> for a similar policy for the <span class="target" id="index-0-command:set"></span><a class="reference internal" href="../command/set.html#command:set" title="set"><code class="xref cmake cmake-command docutils literal notranslate"><span class="pre">set(CACHE)</span></code></a> |
| command, but note that there are some differences in <code class="docutils literal notranslate"><span class="pre">NEW</span></code> behavior |
| between the two policies.</p> |
| <p>This policy was introduced in CMake version 3.13. CMake version |
| 3.23.1 warns when the policy is not set and uses <code class="docutils literal notranslate"><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 notranslate"><span class="pre">cmake_policy()</span></code></a> command to set it to <code class="docutils literal notranslate"><span class="pre">OLD</span></code> or <code class="docutils literal notranslate"><span class="pre">NEW</span></code> |
| explicitly within a project. Use the <span class="target" id="index-0-variable:CMAKE_POLICY_DEFAULT_CMP<NNNN>"></span><a class="reference internal" href="../variable/CMAKE_POLICY_DEFAULT_CMPNNNN.html#variable:CMAKE_POLICY_DEFAULT_CMP<NNNN>" title="CMAKE_POLICY_DEFAULT_CMP<NNNN>"><code class="xref cmake cmake-variable docutils literal notranslate"><span class="pre">CMAKE_POLICY_DEFAULT_CMP0077</span></code></a> variable to set the policy for |
| a third-party project in a subdirectory without modifying it.</p> |
| <div class="admonition note"> |
| <p class="admonition-title">Note</p> |
| <p>The <code class="docutils literal notranslate"><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 notranslate"><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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