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Section: 23.4.3.7.8 [string.swap] Status: TC1 Submitter: Jack Reeves Opened: 1997-12-11 Last modified: 2016-11-12
Priority: Not Prioritized
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Duplicate of: 87
Discussion:
At the very end of the basic_string class definition is the signature: int compare(size_type pos1, size_type n1, const charT* s, size_type n2 = npos) const; In the following text this is defined as: returns basic_string<charT,traits,Allocator>(*this,pos1,n1).compare( basic_string<charT,traits,Allocator>(s,n2);
Since the constructor basic_string(const charT* s, size_type n, const Allocator& a = Allocator()) clearly requires that s != NULL and n < npos and further states that it throws length_error if n == npos, it appears the compare() signature above should always throw length error if invoked like so: str.compare(1, str.size()-1, s); where 's' is some null terminated character array.
This appears to be a typo since the obvious intent is to allow either the call above or something like: str.compare(1, str.size()-1, s, strlen(s)-1);
This would imply that what was really intended was two signatures int compare(size_type pos1, size_type n1, const charT* s) const int compare(size_type pos1, size_type n1, const charT* s, size_type n2) const; each defined in terms of the corresponding constructor.
Proposed resolution:
Replace the compare signature in 23.4.3 [basic.string] (at the very end of the basic_string synopsis) which reads:
int compare(size_type pos1, size_type n1,
const charT* s, size_type n2 = npos) const;
with:
int compare(size_type pos1, size_type n1,
const charT* s) const;
int compare(size_type pos1, size_type n1,
const charT* s, size_type n2) const;
Replace the portion of 23.4.3.7.8 [string.swap] paragraphs 5 and 6 which read:
int compare(size_type pos, size_type n1,
charT * s, size_type n2 = npos) const;
Returns:
basic_string<charT,traits,Allocator>(*this, pos, n1).compare(
basic_string<charT,traits,Allocator>( s, n2))
with:
int compare(size_type pos, size_type n1,
const charT * s) const;
Returns:
basic_string<charT,traits,Allocator>(*this, pos, n1).compare(
basic_string<charT,traits,Allocator>( s ))
int compare(size_type pos, size_type n1,
const charT * s, size_type n2) const;
Returns:
basic_string<charT,traits,Allocator>(*this, pos, n1).compare(
basic_string<charT,traits,Allocator>( s, n2))
Editors please note that in addition to splitting the signature, the third argument becomes const, matching the existing synopsis.
Rationale:
While the LWG dislikes adding signatures, this is a clear defect in the Standard which must be fixed. The same problem was also identified in issues 7 (item 5) and 87.