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| <div class="section" id="checktypesize"> |
| <span id="module:CheckTypeSize"></span><h1>CheckTypeSize<a class="headerlink" href="#checktypesize" title="Permalink to this headline">ΒΆ</a></h1> |
| <p>Check sizeof a type</p> |
| <div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">CHECK_TYPE_SIZE</span><span class="p">(</span><span class="n">TYPE</span> <span class="n">VARIABLE</span> <span class="p">[</span><span class="n">BUILTIN_TYPES_ONLY</span><span class="p">]</span> |
| <span class="p">[</span><span class="n">LANGUAGE</span> <span class="o"><</span><span class="n">language</span><span class="o">></span><span class="p">])</span> |
| </pre></div> |
| </div> |
| <p>Check if the type exists and determine its size. On return, |
| “HAVE_${VARIABLE}” holds the existence of the type, and “${VARIABLE}” |
| holds one of the following:</p> |
| <div class="highlight-default"><div class="highlight"><pre><span></span><span class="o"><</span><span class="n">size</span><span class="o">></span> <span class="o">=</span> <span class="nb">type</span> <span class="n">has</span> <span class="n">non</span><span class="o">-</span><span class="n">zero</span> <span class="n">size</span> <span class="o"><</span><span class="n">size</span><span class="o">></span> |
| <span class="s2">"0"</span> <span class="o">=</span> <span class="nb">type</span> <span class="n">has</span> <span class="n">arch</span><span class="o">-</span><span class="n">dependent</span> <span class="n">size</span> <span class="p">(</span><span class="n">see</span> <span class="n">below</span><span class="p">)</span> |
| <span class="s2">""</span> <span class="o">=</span> <span class="nb">type</span> <span class="n">does</span> <span class="ow">not</span> <span class="n">exist</span> |
| </pre></div> |
| </div> |
| <p>Both <code class="docutils literal"><span class="pre">HAVE_${VARIABLE}</span></code> and <code class="docutils literal"><span class="pre">${VARIABLE}</span></code> will be created as internal |
| cache variables.</p> |
| <p>Furthermore, the variable “${VARIABLE}_CODE” holds C preprocessor code |
| to define the macro “${VARIABLE}” to the size of the type, or leave |
| the macro undefined if the type does not exist.</p> |
| <p>The variable “${VARIABLE}” may be “0” when CMAKE_OSX_ARCHITECTURES has |
| multiple architectures for building OS X universal binaries. This |
| indicates that the type size varies across architectures. In this |
| case “${VARIABLE}_CODE” contains C preprocessor tests mapping from |
| each architecture macro to the corresponding type size. The list of |
| architecture macros is stored in “${VARIABLE}_KEYS”, and the value for |
| each key is stored in “${VARIABLE}-${KEY}”.</p> |
| <p>If the BUILTIN_TYPES_ONLY option is not given, the macro checks for |
| headers <sys/types.h>, <stdint.h>, and <stddef.h>, and saves results |
| in HAVE_SYS_TYPES_H, HAVE_STDINT_H, and HAVE_STDDEF_H. The type size |
| check automatically includes the available headers, thus supporting |
| checks of types defined in the headers.</p> |
| <p>If LANGUAGE is set, the specified compiler will be used to perform the |
| check. Acceptable values are C and CXX</p> |
| <p>Despite the name of the macro you may use it to check the size of more |
| complex expressions, too. To check e.g. for the size of a struct |
| member you can do something like this:</p> |
| <div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">check_type_size</span><span class="p">(</span><span class="s2">"((struct something*)0)->member"</span> <span class="n">SIZEOF_MEMBER</span><span class="p">)</span> |
| </pre></div> |
| </div> |
| <p>The following variables may be set before calling this macro to modify |
| the way the check is run:</p> |
| <div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">CMAKE_REQUIRED_FLAGS</span> <span class="o">=</span> <span class="n">string</span> <span class="n">of</span> <span class="nb">compile</span> <span class="n">command</span> <span class="n">line</span> <span class="n">flags</span> |
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