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<title>14.1.4 Template instantiation #pragma directives </title>
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<a name="1206330"> </a><font color="#003366" face="Verdana, Arial, Helvetica, sans-serif">14.1.4 Template instantiation #pragma directives</font>
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<a name="1206331"> </a><font size=2 face="Verdana, Arial, Helvetica, sans-serif">Instantiation pragmas can be used to control the instantiation of specific template entities or sets of template entities. There are two instantiation pragmas.</font>
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<p> <font size=2 face="Verdana, Arial, Helvetica, sans-serif"><li ><a name="1206332"> </a>The <font size=2 face=Courier><strong>instantiate</strong></font> pragma causes a specified entity to be instantiated.</font></p>
<p> <font size=2 face="Verdana, Arial, Helvetica, sans-serif"><li ><a name="1206333"> </a>The <font size=2 face=Courier><strong>do_not_instantiate</strong></font> pragma suppresses the instantiation of a specified entity. It is typically used to suppress the instantiation of an entity for which a specific definition will be supplied.</font></p>
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<a name="1206442"> </a><font size=2 face="Verdana, Arial, Helvetica, sans-serif">The argument to the instantiation pragma may be:</font>
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<p> <font size=2 face="Verdana, Arial, Helvetica, sans-serif"><li ><a name="1206443"> </a>a template class name - <font size=2 face=Courier><strong>A<int></strong></font>,</font></p>
<p> <font size=2 face="Verdana, Arial, Helvetica, sans-serif"><li ><a name="1206444"> </a>a template class declaration - <font size=2 face=Courier><strong>class A<int></strong></font>,</font></p>
<p> <font size=2 face="Verdana, Arial, Helvetica, sans-serif"><li ><a name="1206341"> </a>a member function name - <font size=2 face=Courier><strong>A<int>::f</strong></font><font face="Verdana, Arial, Helvetica, sans-serif">,</font></font></p>
<p> <font size=2 face="Verdana, Arial, Helvetica, sans-serif"><li ><a name="1206342"> </a>a static data member name - <font size=2 face=Courier><strong>A<int>::i</strong></font>,</font></p>
<p> <font size=2 face="Verdana, Arial, Helvetica, sans-serif"><li ><a name="1206450"> </a>a static data declaration - <font size=2 face=Courier><strong>int A<int>::i</strong></font>,</font></p>
<p> <font size=2 face="Verdana, Arial, Helvetica, sans-serif"><li ><a name="1206451"> </a>a member function declaration - <font size=2 face=Courier><strong>void A<int>::f(int, char)</strong></font>,</font></p>
<p> <font size=2 face="Verdana, Arial, Helvetica, sans-serif"><li ><a name="1206452"> </a>a template function declaration - <font size=2 face=Courier><strong>char* f(int, float)</strong></font>.</font></p>
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<a name="1206346"> </a><font size=2 face="Verdana, Arial, Helvetica, sans-serif">A pragma in which the argument is a template class name (for example, <font size=2 face=Courier><strong>A<int></strong></font> or <font size=2 face=Courier><strong>class A<int></strong></font>) is equivalent to repeating the pragma for each member function and static data member declared in the class. When instantiating an entire class, a given member function or static data member may be excluded using the <font size=2 face=Courier><strong>do_not_instantiate</strong></font> pragma.</font>
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<a name="1207729"> </a><font size=2 face="Verdana, Arial, Helvetica, sans-serif">For example, </font>
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<a name="1206347"> </a><font size=2 face=Courier><strong>#pragma instantiate A<int><br>#pragma do_not_instantiate A<int>::f<br></strong></font>
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<a name="1206348"> </a><font size=2 face="Verdana, Arial, Helvetica, sans-serif">The template definition of a template entity must be present in the compilation for an instantiation to occur. If an instantiation is explicitly requested by use of the <font size=2 face=Courier><strong>instantiate</strong></font> pragma and no template definition is available or specific definition is provided, the compiler issues an error. </font>
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<a name="1206488"> </a><font size=2 face=Courier><strong>template <class T> void f1(T); ⌨️ 快捷键说明
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