When the regex_constants::collate flag is set, character ranges fail to match characters according to the locale's collation order.
Test case
#include <iostream>
#include <locale>
#include <regex>
using namespace std;
int main() {
const locale de("de_DE");
regex_traits<wchar_t> traits;
traits.imbue(de);
wregex re(L"[a-z]", regex_constants::collate);
re.imbue(de);
const wchar_t eszett = L'ß';
const wchar_t s = L's';
const wchar_t t = L't';
const wchar_t ss[] = {L's', L's'};
const wchar_t minus = L'-';
const auto stransform = traits.transform(&s, &s + 1);
const auto ttransform = traits.transform(&t, &t + 1);
const auto eszetttransform = traits.transform(&eszett, &eszett + 1);
const auto sstransform = traits.transform(begin(ss), end(ss));
cout << regex_match(L"ß", re) << '\n';
cout << (stransform <= eszetttransform
&& eszetttransform <= ttransform)
<< ' '
<< (sstransform == eszetttransform)
<< '\n';
return 0;
}Godbolt link
Expected behavior
The range should match ß, since ß collates like ss and should be sorted between s and t (and thus between a and z as well). Hence, the output of this program should be:
Actual behavior
The range does not match ß, so the actual output is:
Note that the output of the second line shows that the problem does not lie in the implementation of regex_traits<wchar_t>::transform, as it returns sort keys that are equal for ß and ss and place ß between s and t.
When the
regex_constants::collateflag is set, character ranges fail to match characters according to the locale's collation order.Test case
Godbolt link
Expected behavior
The range should match
ß, sinceßcollates likessand should be sorted betweensandt(and thus betweenaandzas well). Hence, the output of this program should be:Actual behavior
The range does not match
ß, so the actual output is:Note that the output of the second line shows that the problem does not lie in the implementation of
regex_traits<wchar_t>::transform, as it returns sort keys that are equal forßandssand placeßbetweensandt.