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2235. Undefined behavior without proper requirements onbasic_string constructors

Section: 27.4.3.3[string.cons]Status:C++14Submitter: Juan SoulieOpened: 2013-01-17Last modified: 2016-01-28

Priority:Not Prioritized

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Discussion:

In 27.4.3.3[string.cons], I believe tighter requirements should be imposed onbasic_string's constructors taking ans argument (or, a behavior should be provided for the undefined cases).These requirements are properly stated in the other members functions takings arguments (append,assign,insert,...).

basic_string(const charT* s, size_type n, const Allocator& a = Allocator());

Relative to N3485, 27.4.3.3[string.cons]/6 says "Requires:s shall not be a null pointer andn < npos", where it should say: "Requires:s points to an array of at leastn elements ofcharT"

basic_string(const charT* s, const Allocator& a = Allocator());

27.4.3.3[string.cons]/8 says "Requires:s shall not be a null pointer.", where it should say:"Requires:s points to an array of at leasttraits::length(s) + 1 elements ofcharT"

Daniel:

I think that 16.4.5.9[res.on.arguments] p1 b2 basically requires this already, but the wording is indeed worth improving it.

[2013-03-15 Issues Teleconference]

Moved to Review.

The resolution could be worded more cleanly, and there is some concern about redundancy betweenRequirements andEffects clauses. Consensus that we do want to say something likethis for theRequirements though.

[2013-04-18, Bristol]

Move to Ready

[2013-09-29, Bristol]

Apply to the Working Paper

Proposed resolution:

This wording is relative to N3485.

1. Change 27.4.3.3[string.cons]/6 as indicated:

   basic_string(const charT* s, size_type n, const Allocator& a = Allocator());

   -6-Requires:sshall not be a null pointer andn < npospoints to an array of at leastn elements ofcharT.

2. Change 27.4.3.3[string.cons]/8 as indicated:

   basic_string(const charT* s, const Allocator& a = Allocator());

   -8-Requires:sshall not be a null pointerpoints to an array of at leasttraits::length(s) + 1 elements ofcharT.