NAME¶

std::experimental::make_unique_resource_checked - std::experimental::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>> (library
make_unique_resource_checked( R&& r, const S& invalid, D&& fundamentals 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 contextually
converted to bool, and the behavior is undefined if the conversion results 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