path_from_handle using GetModuleFileNameW in wrong way

[Agile86]

boost\dll\detail\windows\path_from_handle.hpp

        boost::detail::winapi::GetModuleFileNameW(handle, path_hldr, 
            DEFAULT_PATH_SIZE_);
        ec = last_error_code();
        if (!ec) {
            return boost::filesystem::path(path_hldr);
        }

The problem here is that code doesn't analyze return code. If GetLastError() was dirty before a call this code will fail even if GetModuleFileNameW() will success. Yes, on success, GetModuleFileNameW() doesn't reset last error to ERROR_SUCCESS.

[apolukhin]

Many thanks for reporting the issue!

[Oberon00]

I don't think the fix in f04ceff is correct, as calling GetLastError does not reset the error code. Instead, as @Agile86 said, you should check the return value of GetModuleFileNameW and call GetLastError only if the return value indicates an error (i.e. if the return value equals zero or DEFAULT_PATH_SIZE_ in this case).

I think, even setting the error code to zero beforehand is not guaranteed to work as the function might internally cause and handle an error reported via GetLastError without setting the error code to zero afterwards.

[muggenhor]

The chosen solution definitely doesn't work:

#include <assert.h>
#include <windows.h>

int main()
{
  SetLastError(42u);
  GetLastError(); // <-- we depend on this resetting the error code (it doesn't)
  assert(GetLastError() == ERROR_SUCCESS);
  return 0;
}

Leads to:

Assertion failed!

Program: Z:\home\vanschig\git\novaui\thirdparty\test.exe
File: test.cpp, Line 8

Expression: GetLastError() == ERROR_SUCCESS

abnormal program termination