19 Diagnostics library [diagnostics]

19.5 System error support [syserr]

19.5.8 Class system_error [syserr.syserr]

19.5.8.1 Overview [syserr.syserr.overview]

1
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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
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[Note 1: 
If an error represents an out-of-memory condition, implementations are encouraged to throw an exception object of type bad_alloc rather than system_error.
— end note]
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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; }; }

19.5.8.2 Members [syserr.syserr.members]

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