[NaCl SDK] nacl_io example: Check ferror() after reading/writing.

native_client_sdk/src/examples/demo/nacl_io/handlers.c

 /* Copyright (c) 2012 The Chromium Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "handlers.h"
 
 #include <assert.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ skipping 146 matching lines @@
   data_len = strlen(data);
 
   if (!file) {
     *output = PrintfToNewString("Error: Unknown file handle %s.",
                                 file_index_string);
     return 2;
   }
 
   bytes_written = fwrite(data, 1, data_len, file);
 
+  if (ferror(file)) {
+    *output = PrintfToNewString(
+        "Error: Wrote %d bytes, but ferror() returns true.", bytes_written);
+    return 3;
+  }
+
   *output = PrintfToNewString("fwrite\1%s\1%d", file_index_string,
                               bytes_written);
   return 0;
 }
 
 /**
  * Handle a call to fread() made by JavaScript.
  *
  * fread expects 2 parameters:
  *   0: The index of the file (which is mapped to a FILE*)
@@ skipping 27 matching lines @@
   if (!file) {
     *output = PrintfToNewString("Error: Unknown file handle %s.",
                                 file_index_string);
     return 2;
   }
 
   buffer = (char*)malloc(data_len + 1);
   bytes_read = fread(buffer, 1, data_len, file);
   buffer[bytes_read] = 0;
 
+  if (ferror(file)) {
+    *output = PrintfToNewString(
+        "Error: Read %d bytes, but ferror() returns true.", bytes_read);
+    return 3;
+  }
+
   *output = PrintfToNewString("fread\1%s\1%s", file_index_string, buffer);
   free(buffer);
   return 0;
 }
 
 /**
  * Handle a call to fseek() made by JavaScript.
  *
  * fseek expects 3 parameters:
  *   0: The index of the file (which is mapped to a FILE*)
@@ skipping 89 matching lines @@
   if (result) {
     *output = PrintfToNewString("Error: fclose returned error %d.", result);
     return 3;
   }
 
   RemoveFileFromMap(file_index);
 
   *output = PrintfToNewString("fclose\1%s", file_index_string);
   return 0;
 }