EventLogChannel::EventLogChannel():
_logFile("Application"),
_h(0)
{
#if defined(POCO_WIN32_UTF8)
wchar_t name[256];
int n = GetModuleFileNameW(NULL, name, sizeof(name));
// ...
}

wchar_t name[256];
// -> array with 256 elements created

int n = GetModuleFileNameW(NULL, name, sizeof(name));
// -> Try to read 512 elements !!! because the length of one wchar_t is 2

EventLogChannel::EventLogChannel():
_logFile("Application"),
_h(0)
{
static const int length = 256;
#if defined(POCO_WIN32_UTF8)
wchar_t name[length];
int n = GetModuleFileNameW(NULL, name, length);
// ...
}