std::experimental:: make_unique_resource_checked

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.

Paramaters

Reture value

A unique_resource described above.

Exceptions

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

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

#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 exists.");
    else
        std::puts("The file does not exist.");
}

The file does not exist.

See also