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Fix using std::reverse() with wxString iterators in a proper way

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The solution with specializing std::iter_swap() for wxString::iterator
was not conforming as the iterator was still not swappable, as it is
required to be.

Fix this by providing std::swap() overload for wxString::iterator, which
is correct and even simpler.

This allows std::reverse(s.begin(), s.end()) work with clang too and
incidentally avoids warnings about the code relying on non-conforming
extensions with MSVS 2017 which were due to the fact that iter_swap()
workaround wasn't enabled for it, while the new swap() overload is.
This commit is contained in:
Vadim Zeitlin
2019-04-26 03:10:16 +02:00
parent a1b39ce78b
commit 91b3bfedf8
3 changed files with 17 additions and 32 deletions
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26
include/wx/string.h
View File

@@ -3980,32 +3980,6 @@ namespace std
#endif // C++11
// Specialize std::iter_swap in C++11 to make std::reverse() work with wxString
// iterators: unlike in C++98, where iter_swap() is required to deal with the
// iterator::reference being different from "iterator::value_type&", in C++11
// iter_swap() just calls swap() by default and this doesn't work for us as
// wxUniCharRef is not the same as "wxUniChar&".
//
// Unfortunately currently iter_swap() can't be specialized when using libc++,
// see https://llvm.org/bugs/show_bug.cgi?id=28559
#if (__cplusplus >= 201103L) && !defined(_LIBCPP_VERSION)
namespace std
{
template <>
inline void
iter_swap<wxString::iterator>(wxString::iterator i1, wxString::iterator i2)
{
// We don't check for i1 == i2, this won't happen in normal use, so
// don't pessimize the common code to account for it.
wxUniChar tmp = *i1;
*i1 = *i2;
*i2 = tmp;
}
} // namespace std
#endif // C++11
// ---------------------------------------------------------------------------
// Implementation only from here until the end of file
// ---------------------------------------------------------------------------

17
include/wx/unichar.h
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@@ -360,6 +360,23 @@ void swap<wxUniCharRef>(wxUniCharRef& lhs, wxUniCharRef& rhs)
} // namespace std
#if __cplusplus >= 201103L || wxCHECK_VISUALC_VERSION(10)
// For std::iter_swap() to work with wxString::iterator, which uses
// wxUniCharRef as its reference type, we need to ensure that swap() works with
// wxUniCharRef objects by defining this overload.
//
// See https://bugs.llvm.org/show_bug.cgi?id=28559#c9
inline
void swap(wxUniCharRef&& lhs, wxUniCharRef&& rhs)
{
wxUniChar tmp = lhs;
lhs = rhs;
rhs = tmp;
}
#endif // C++11
// Comparison operators for the case when wxUniChar(Ref) is the second operand
// implemented in terms of member comparison functions

6
tests/strings/stdstrings.cpp
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@@ -626,13 +626,7 @@ void StdStringTestCase::StdConversion()
void StdStringTestCase::StdAlgo()
{
// Unfortunately this currently doesn't work with libc++ in C++11 mode, see
// comment near iter_swap() definition in wx/string.h.
#if __cplusplus < 201103L || !defined(_LIBCPP_VERSION)
wxString s("AB");
std::reverse(s.begin(), s.end());
CPPUNIT_ASSERT_EQUAL( "BA", s );
#else
wxLogWarning("Skipping std::reverse() test broken with C++11/libc++");
#endif
}