Re: Using non-const predicate in std::map fails to compile in release
On 6 Okt, 16:27, =B9=D8=D3=DAMS=B5=C4parport IOCTL
<MSparportIO...@discussions.microsoft.com> wrote:
#include <iostream>
#include <functional>
#include <map>
#include <cassert>
#include <tchar.h>
using namespace std;
int _tmain(int argc, _TCHAR* argv[])
{
struct c_wstring_compare
: std::binary_function<const wchar_t *, const wchar_t *, bool>
{
inline result_type
operator()(first_argument_type left, second_argument_type rig=
ht)
{
return wcscmp(left, right) < 0;
}
};
typedef map<const wchar_t *, const wchar_t *, c_wstring_compare>
MyCharMap;
MyCharMap container;
container.find(_T("key2"));
return 0;
}
The code above can be compiled successfully in debug mode while fails in
release mode (visual studio 2008).
The error message is:
E:\Microsoft Visual Studio 9.0\VC\include\xtree(1268) : error C3848:
expression having type 'const wmain::c_wstring_compare' would lose some
const-volatile qualifiers in order to call 'bool
wmain::c_wstring_compare::operator ()(const wchar_t *,const wchar_t *)'
Should it be regarded as a defect?
I reported this earlier this year. See:
http://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?Feedba=
ckID=328343
For the record, the predicate is required to be const because of the
definition of class value_compare.