Section: 27.2.4.2 [char.traits.specializations.char] Status: CD1 Submitter: Martin Sebor Opened: 2004-06-28 Last modified: 2016-01-28
Priority: Not Prioritized
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Discussion:
Table 37 describes the requirements on Traits::compare() in terms of those on Traits::lt(). 21.1.3.1, p6 requires char_traits<char>::lt() to yield the same result as operator<(char, char).
Most, if not all, implementations of char_traits<char>::compare() call memcmp() for efficiency. However, the C standard requires both memcmp() and strcmp() to interpret characters under comparison as unsigned, regardless of the signedness of char. As a result, all these char_traits implementations fail to meet the requirement imposed by Table 37 on compare() when char is signed.
Read email thread starting with c++std-lib-13499 for more.
Proposed resolution:
Change 21.1.3.1, p6 from
The two-argument members assign, eq, and lt are defined identically to the built-in operators =, ==, and < respectively.
to
The two-argument member assign is defined identically to the built-in operator =. The two argument members eq and lt are defined identically to the built-in operators == and < for type unsigned char.
[Redmond: The LWG agreed with this general direction, but we
also need to change eq to be consistent with this change.
Post-Redmond: Martin provided wording.]