win32: support logging to command line

src/win32/yass.cpp

@@ -53,6 +53,21 @@ int APIENTRY wWinMain(_In_ HINSTANCE hInstance,
     return -1;
   }
 
+  // This function is primarily useful to applications that were linked with /SUBSYSTEM:WINDOWS,
+  // which implies to the operating system that a console is not needed
+  // before entering the program's main method.
+  if (AttachConsole(ATTACH_PARENT_PROCESS) != 0) {
+    FILE* unusedFile;
+    // Swap to the new out/err streams
+    freopen_s(&unusedFile, "CONOUT$", "w", stdout);
+    freopen_s(&unusedFile, "CONOUT$", "w", stderr);
+    std::cout.clear();
+    std::clog.clear();
+    std::cerr.clear();
+    fprintf(stderr, "attached to parent process\n");
+    fflush(stderr);
+  }
+
   if (!SetUTF8Locale()) {
     LOG(WARNING) << "Failed to set up utf-8 locale";
   }