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Edward Diener
2019-10-06 22:20:19 -04:00
parent 88a0365f4d
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doc/ref/variadic_opt.html
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@ -16,6 +16,19 @@ Expands to 1 if the __VA_OPT__ construct is supported, otherwise expands to 0.
<dt>None<br>
</dt>
</dl>
<h4>Remarks</h4>
<div>
This macro only returns 1 if the compiler is compiling at its own C++20 level and
__VA_OPT__ is supported. It is possible for a compiler to support the __VA_OPT__
construct when not compiling at its own C++20 level, but this macro will return
0 in that case even if __VA_OPT__ is normally supported for that level. The reason
for this is that such a compiler may have a compiler switch, enforcing a strict
adherence to a particular C++ standard level, which gives a warning or an error
if __VA_OPT__ is specified below the C++20 level, and the preprocessor library
wants to avoid that happening. Therefore the macro will only test to see whether
or not __VA_OPT__ is supported at the C++20 level, while otherwise always returning
0 for all lesser C++ standard levels.
</div>
<h4>Requirements</h4>
<div> <b>Header:</b> &nbsp;<a href="../headers/variadic/opt.html">&lt;boost/preprocessor/variadic/opt.hpp&gt;</a>
</div>