std::experimental::make_unique_resource_checked
| Defined in header <experimental/scope>
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| template< class R, class D, class S = std::decay_t<R> > std::experimental::unique_resource<std::decay_t<R>, std::decay_t<D>> |
(library fundamentals TS v3) | |
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
| r | - | a resource handle |
| d | - | a deleter to use to dispose the resource |
| invalid | - | a value indicating the resource handle is invalid |
Reture value
A unique_resource described above.
Exceptions
Any exception thrown in initialization of the stored resource handle and the deleter.
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
#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."); }
Possible output:
The file does not exist.