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- <a name="variadic_macro_data.vmd_vmacros"></a><a class="link" href="vmd_vmacros.html" title="Using variadic macros">Using variadic macros</a>
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- <p>
- Variadic macros, as specified by C++11, is a feature taken from the C99 specification.
- They are macros which take a final parameter denoted as '...' which represents
- one or more final arguments to the macro as a series of comma-separated tokens.
- In the macro expansion a special keyword of '__VA_ARGS__' represents the comma-separated
- tokens. This information when passed to a variadic macro I call 'variadic macro
- data', which gives its name to this library. The more general term 'variadic
- data' is used in this documentation to specify data passed to a macro which
- can contain any number of macro tokens as a single macro parameter, such as
- is found in Boost PP data types.
- </p>
- <h4>
- <a name="variadic_macro_data.vmd_vmacros.h0"></a>
- <span class="phrase"><a name="variadic_macro_data.vmd_vmacros.boost_support"></a></span><a class="link" href="vmd_vmacros.html#variadic_macro_data.vmd_vmacros.boost_support">Boost
- support</a>
- </h4>
- <p>
- The Boost PP library has support for variadic macros and uses its own criteria
- to determine if a particular compiler has that support. Boost PP defines or
- uses the macro BOOST_PP_VARIADICS to denote whether the compiler being used
- supports variadic macros. When BOOST_PP_VARIADICS is set to 1 the compiler
- supports variadic macros, otherwise when BOOST_PP_VARIADICS is set to 0 the
- compiler does not support variadic macros. If a user of Boost PP sets this
- value, Boost PP uses the value the end-user sets, otherwise Boost PP defines
- the value of BOOST_PP_VARIADICS based on its own analysis of the compiler being
- used. This macro can also be checked to determine if a compiler has support
- for variadic macros.
- </p>
- <h4>
- <a name="variadic_macro_data.vmd_vmacros.h1"></a>
- <span class="phrase"><a name="variadic_macro_data.vmd_vmacros.determining_variadic_macro_suppo"></a></span><a class="link" href="vmd_vmacros.html#variadic_macro_data.vmd_vmacros.determining_variadic_macro_suppo">Determining
- variadic macro support</a>
- </h4>
- <p>
- The VMD library automatically determines whether variadic macro support is
- enabled for a particular compiler by also using the same BOOST_PP_VARIADICS
- macro from Boost PP. The end-user of VMD can also manually set the macro BOOST_PP_VARIADICS
- to turn on or off compiler support for variadic macros in the VMD library.
- When BOOST_PP_VARIADICS is set to 0 variadic macros are not supported in the
- VMD library, otherwise when BOOST_PP_VARIADICS is set to non-zero they are
- supported in the VMD library. This same macro can be used to determine if VMD
- supports variadic macros for a particular compiler.
- </p>
- <p>
- Since this library depends on variadic macro support, if BOOST_PP_VARIADICS
- is set to 0, using any of the macros in VMD will lead to a compiler error since
- the macro will not be defined. However just including any of the header files
- in VMD, even with no variadic macro support for the compiler, will not lead
- to any compiler errors.
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