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4023. Preconditions of std::basic_streambuf::setg/setp

Section: 31.6.3.4 [streambuf.protected] Status: WP Submitter: Jiang An Opened: 2023-12-08 Last modified: 2024-04-02

Priority: Not Prioritized

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Discussion:

It seems that operations of std::basic_streambuf expect that

• [eback(), egptr()) is a valid range and gptr() points into that range, and

• [pbase(), pptr()) is a valid range and epptr() points into that range.

However, it is currently not specified for setg/setp that such invariants need to be established.

[2024-03-11; Reflector poll]

Set status to Tentatively Ready after six votes in favour during reflector poll.

[Tokyo 2024-03-23; Status changed: Voting → WP.]

Proposed resolution:

This wording is relative to N4964.

1. Modify 31.6.3.4.2 [streambuf.get.area] as indicated:

   void setg(char_type* gbeg, char_type* gnext, char_type* gend);
   

   -?- Preconditions: [gbeg, gnext), [gbeg, gend), and [gnext, gend) are all valid ranges.

   -5- Postconditions: gbeg == eback(), gnext == gptr(), and gend == egptr() are all true.

2. Modify 31.6.3.4.3 [streambuf.put.area] as indicated:

   void setp(char_type* pbeg, char_type* pend);
   

   -?- Preconditions: [pbeg, pend) is a valid range.

   -5- Postconditions: pbeg == pbase(), pbeg == pptr(), and pend == epptr() are all true.