22 Diagnostics library [diagnostics]

22.5 System error support [syserr]

22.5.7 Class system_­error [syserr.syserr]

22.5.7.1 Class system_­error overview [syserr.syserr.overview]

1
#
The class system_­error describes an exception object used to report error conditions that have an associated error code.
Such error conditions typically originate from the operating system or other low-level application program interfaces.
2
#
[ Note
:
If an error represents an out-of-memory condition, implementations are encouraged to throw an exception object of type bad_­alloc ([bad.alloc]) rather than system_­error.
— end note
 ]
namespace std {
  class system_error : public runtime_error {
  public:
    system_error(error_code ec, const string& what_arg);
    system_error(error_code ec, const char* what_arg);
    system_error(error_code ec);
    system_error(int ev, const error_category& ecat, const string& what_arg);
    system_error(int ev, const error_category& ecat, const char* what_arg);
    system_error(int ev, const error_category& ecat);
    const error_code& code() const noexcept;
    const char* what() const noexcept override;
  };
}

22.5.7.2 Class system_­error members [syserr.syserr.members]

system_error(error_code ec, const string& what_arg);
1
#
Effects: Constructs an object of class system_­error.
2
#
Postconditions: code() == ec.
string(what()).find(what_­arg) != string​::​npos.
system_error(error_code ec, const char* what_arg);
3
#
Effects: Constructs an object of class system_­error.
4
#
Postconditions: code() == ec.
string(what()).find(what_­arg) != string​::​npos.
system_error(error_code ec);
5
#
Effects: Constructs an object of class system_­error.
6
#
Postconditions: code() == ec.
system_error(int ev, const error_category& ecat, const string& what_arg);
7
#
Effects: Constructs an object of class system_­error.
8
#
Postconditions: code() == error_­code(ev, ecat).
string(what()).find(what_­arg) != string​::​npos.
system_error(int ev, const error_category& ecat, const char* what_arg);
9
#
Effects: Constructs an object of class system_­error.
10
#
Postconditions: code() == error_­code(ev, ecat).
string(what()).find(what_­arg) != string​::​npos.
system_error(int ev, const error_category& ecat);
11
#
Effects: Constructs an object of class system_­error.
12
#
Postconditions: code() == error_­code(ev, ecat).
const error_code& code() const noexcept;
13
#
Returns: ec or error_­code(ev, ecat), from the constructor, as appropriate.
const char* what() const noexcept override;
14
#
Returns: An ntbs incorporating the arguments supplied in the constructor.
[ Note
:
The returned ntbs might be the contents of what_­arg + ": " + code.message().
— end note
 ]