test overloads

Synopses

Declared in <bslstl_sharedptr.h>

This function is never defined. It provides a property‐checker that an entity of (template parameter) type FACTORY can be called like a function with a single argument, which is a pointer to an object of (template parameter) type ARG. The sizeof() expression provides an unevaluated context to check the validity of the enclosed expression, and the , 0 ensures that the sizeof check remains valid, even if the expression returns void. Similarly, the cast to void ensures that there are no surprises with types that overload the comma operator. Note that the cast to void is elided for Clang compilers using versions of LLVM prior to 12, which fail to evaluate the trait properly. Note that sizeof(decltype()) is required for MSVC due to a compiler bug in MSVC 17.6 and later (at least including 17.7.0 Preview 2.0).

template<class ARG>
static
FalseType
test(...);

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Overload selected when FUNCTOR is callable with ARG.

template<class ARG>
static
TrueType
test(bsl::enable_if<static_cast<bool>(sizeof static_cast<void>(Util::declval<FUNCTOR>()(Util::declval<ARG>() , 0)))>::type*);

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