[lldb] [Commands] Fix reporting errors in 'platform file read/write'

[mgorny]

Summary

Fix 'platform file read' and 'platform file write' commands to correctly
detect erraneous return and report it as such. Currently, errors were
implicitly printed as a return value of -1, and the commands were
assumed to be successful.

[mgorny]

Fix integer type mismatches.

lldb/source/Commands/CommandObjectPlatform.cpp

if (platform_sp) {
       lldb::user_id_t fd;
       if (!llvm::to_integer(cmd_line, fd)) {
         result.AppendErrorWithFormatv("'{0}' is not a valid file descriptor.\n",
                                       cmd_line);
         return result.Succeeded();
       }
       std::string buffer(m_options.m_count, 0);
       Status error;
-      uint32_t retcode = platform_sp->ReadFile(
+      uint64_t retcode = platform_sp->ReadFile(
           fd, m_options.m_offset, &buffer[0], m_options.m_count, error);
-      result.AppendMessageWithFormat("Return = %d\n", retcode);
+      if (retcode != UINT64_MAX) {
+        result.AppendMessageWithFormat("Return = %" PRIu64 "\n", retcode);
         result.AppendMessageWithFormat("Data = \"%s\"\n", buffer.c_str());
         result.SetStatus(eReturnStatusSuccessFinishResult);
       } else {
+        result.AppendError(error.AsCString());
+      }
+    } else {
       result.AppendError("no platform currently selected\n");
     }
     return result.Succeeded();
   }
 
   Options *GetOptions() override { return &m_options; }
 
 protected:
if (platform_sp) {
       args.GetCommandString(cmd_line);
       Status error;
       lldb::user_id_t fd;
       if (!llvm::to_integer(cmd_line, fd)) {
         result.AppendErrorWithFormatv("'{0}' is not a valid file descriptor.",
                                       cmd_line);
         return result.Succeeded();
       }
-      uint32_t retcode =
+      uint64_t retcode =
           platform_sp->WriteFile(fd, m_options.m_offset, &m_options.m_data[0],
                                  m_options.m_data.size(), error);
-      result.AppendMessageWithFormat("Return = %d\n", retcode);
+      if (retcode != UINT64_MAX) {
+        result.AppendMessageWithFormat("Return = %" PRIu64 "\n", retcode);
         result.SetStatus(eReturnStatusSuccessFinishResult);
       } else {
+        result.AppendError(error.AsCString());
+      }
+    } else {
       result.AppendError("no platform currently selected\n");
     }
     return result.Succeeded();
   }
 
   Options *GetOptions() override { return &m_options; }
 
 protected:

lldb/test/API/functionalities/gdb_remote_client/TestGDBRemotePlatformFile.py

def test_file_fail(self):
             self.runCmd("platform select remote-gdb-server")
             self.runCmd("platform connect connect://" +
                         self.server.get_connect_address())
             self.assertTrue(self.dbg.GetSelectedPlatform().IsConnected())
 
             self.match("platform file open /some/file.txt -v 0755",
                        [r"error: Invalid argument"],
                        error=True)
-            # TODO: fix the commands to fail on unsuccessful result
             self.match("platform file read 16 -o 11 -c 13",
-                       [r"Return = -1\nData = \"\""])
+                       [r"error: Invalid argument"],
+                       error=True)
             self.match("platform file write 16 -o 11 -d teststring",
-                       [r"Return = -1"])
+                       [r"error: Invalid argument"],
+                       error=True)
             self.match("platform file close 16",
                        [r"error: Invalid argument"],
                        error=True)
             self.assertPacketLogContains([
                 "vFile:open:2f736f6d652f66696c652e747874,0000020a,000001ed",
                 "vFile:pread:10,d,b",
                 "vFile:pwrite:10,b,teststring",
                 "vFile:close:10",
                 ])
         finally:
             self.dbg.GetSelectedPlatform().DisconnectRemote()