check for interrupt from fgets on Windows

[lanza]

Summary

Windows does not have the error EINTR when a blocking syscall is
interrupted by a signal. The ReadFile API that fgets is implemented
with instead use ERROR_OPERATION_ABORTED. Check for that after fgets.

[aleksandr.urakov]

LGTM!

[lanza]

This actually doesn't seem to be working due to a bug in Windows' ReadFile. https://github.com/microsoft/terminal/issues/334 @stella.stamenova any idea about this?

[lanza]

rebase

source/Core/IOHandler.cpp

#ifdef _WIN32
         // ReadFile on Windows is supposed to set ERROR_OPERATION_ABORTED
         // according to the docs on MSDN. However, this has evidently been a
         // known bug since Windows 8. Therefore, we can't detect if a signal
         // interrupted in the fgets. So pressing ctrl-c causes the repl to end
         // and the process to exit. A temporary workaround is just to attempt to
         // fgets twice until this bug is fixed.
         if (fgets(buffer, sizeof(buffer), in) == nullptr &&
             fgets(buffer, sizeof(buffer), in) == nullptr) {
+          // this is the equivalent of EINTR for Windows
+          if (GetLastError() == ERROR_OPERATION_ABORTED)
+            continue;
 #else
         if (fgets(buffer, sizeof(buffer), in) == nullptr) {
 #endif
           const int saved_errno = errno;
           if (feof(in))
             done = true;
           else if (ferror(in)) {
             if (saved_errno != EINTR)