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std::experi...urce_checked(3)  C++ Standard Libary std::experi...urce_checked(3)

NAME
     std::experimental::make_unique_resource_checked	  -	 std::experimen-
     tal::make_unique_resource_checked

Synopsis
	Defined in header <experimental/scope>
	template< class R, class D, class S = std::decay_t<R> >

	std::experimental::unique_resource<std::decay_t<R>,
	std::decay_t<D>>						    (li-
     brary
	    make_unique_resource_checked(  R&& r, const S& invalid, D&&   funda-
     mentals TS v3)
	d )

	    noexcept(/*see below*/);

	Creates a unique_resource, initializes its  stored  resource  handle  is
     initialized
	with  std::forward<R>(r)  and  its  deleter with std::forward<D>(d). The
     created
	unique_resource owns the resource if and only if bool(r ==  invalid)  is
     false.

	The  program is ill-formed if the expression r == invalid cannot be con-
     textually
	converted to bool, and the behavior is undefined if the  conversion  re-
     sults in
	undefined behavior or throws an exception.

Exceptions
	Any exception thrown in initialization of the stored resource handle and
     the
	deleter.

	noexcept specification:
	noexcept(

	    std::is_nothrow_constructible_v<std::decay_t<R>, R> &&
	    std::is_nothrow_constructible_v<std::decay_t<D>, D>

	)

Notes
	make_unique_resource_checked  exists to avoid calling a deleter function
     with an
	invalid argument.

	Resource handle r is either copied or moved into the return  value,  and
     the created
	unique_resource  always  holds an underlying resource handle with object
     type.

Example
     // Run this code

      #include <cstdio>
      #include <experimental/scope>

      int main()
      {
	  // avoid calling fclose when fopen fails
	  auto file = std::experimental::make_unique_resource_checked(
	      std::fopen("potentially_nonexistent_file.txt", "r"),
	      nullptr,
	      [](std::FILE *fptr) { std::fclose(fptr); }
	  );
	  if (file.get())
	      std::puts("The file exits.");
	  else
	      std::puts("The file does not exist.");
      }

Possible output:
      The file does not exist.

See also
Category:
	  * conditionally noexcept

http://cppreference.com 	   2024.06.10	   std::experi...urce_checked(3)
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