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Assume variadic macro support.

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Edward Diener
2020-09-17 18:25:36 -04:00
parent 8288ce7575
commit 5fd12d32d4
80 changed files with 864 additions and 9334 deletions
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doc/topics/emptiness.html
+8 -10
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@@ -125,13 +125,12 @@
BOOST_PP_VARIADIC_HAS_OPT, which is a function-like macro taking
no parameters and returning 1 if the __VA_OPT__ construct is
supported and 0 if it is not. The macro only returns 1 when
variadic macros are supported, when the compiler is at the C++20
level, and when the __VA_OPT__ construct can be used according to
the C++20 standard. In particular the macro needs the compiler to
be working at the C++20 level despite the fact that at least one
major compiler supports the __VA_OPT__ construct in some of its
latest releases even when the compiler is being used at a C++
standard level below that of C++20. The reason this Boost
the compiler is at the C++20 level, and when the __VA_OPT__ construct
can be used according to the C++20 standard. In particular the macro
needs the compiler to be working at the C++20 level despite the fact
that at least one major compiler supports the __VA_OPT__ construct in
some of its latest releases even when the compiler is being used at a
C++ standard level below that of C++20. The reason this Boost
preprocessor library requires the C++20 level is because that same
major compiler can produce a warning, or even an error, when it
even sees a macro using the __VA_OPT__ construct at a level below
@@ -139,9 +138,8 @@
requiring strict adherence to the level of the C++ standard being
used are passed on the command line. So taking a conservative
approach the BOOST_PP_VARIADIC_HAS_OPT macros requires compilation
at the C++20 level, along with variadic macro support, along with
the testing code expanding to 1, in order to specify that
__VA_OPT__ is supported.<br>
at the C++20 level, along with the testing code expanding to 1,
in order to specify that __VA_OPT__ is supported.<br>
<br>
The actual Boost Preprocessor library for testing for emptiness in
C++20 mode is called BOOST_PP_CHECK_EMPTY. The macro is a variadic