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3053. Prohibit error_code construction from rvalues of error_category

Section: 19.5.4.1 [syserr.errcode.overview] Status: New Submitter: Antony Polukhin Opened: 2018-01-24 Last modified: 2020-09-06

Priority: 3

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Discussion:

Constructor error_code(int val, const error_category& cat) and member function void assign(int val, const error_category& cat) could be misused if a custom error_category is provided:

error_code ec{1, test_category{}}; // ec holds a pointer/reference to a temporary

[2018-06-18 after reflector discussion]

Priority set to 3

Proposed resolution:

This wording is relative to N4713.

1. Modify 19.5.4.1 [syserr.errcode.overview] as indicated:

   namespace std {
     class error_code {
     public:
       // 19.5.4.2 [syserr.errcode.constructors], constructors
       […]
       error_code(int val, const error_category& cat) noexcept;
       error_code(int val, const error_category&& cat) = delete;
       […]
       // 19.5.4.3 [syserr.errcode.modifiers], modifiers
       void assign(int val, const error_category& cat) noexcept;
       void assign(int val, const error_category&& cat) = delete;
       […]
     };
     […]
   }