Fix failure

bin/fdutils_linux.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include <errno.h>
 #include <fcntl.h>
 #include <unistd.h>
 #include <sys/ioctl.h>
 
 #include "bin/fdutils.h"
@@ skipping 21 matching lines @@
   if (status < 0) {
     perror("fcntl F_GETFL failed");
     return false;
   }
   *is_blocking = (status & O_NONBLOCK) == 0;
   return true;
 }
 
 
 intptr_t FDUtils::AvailableBytes(intptr_t fd) {
-  size_t available;
+  int available;  // ioctl for FIONREAD expects an 'int*' argument.
   int result = TEMP_FAILURE_RETRY(ioctl(fd, FIONREAD, &available));
   if (result < 0) {
     return result;
   }
-  return available;
+#ifdef DEBUG
+  ASSERT(available >= 0);
+#endif
+  return static_cast<intptr_t>(available);
 }
 
 
 ssize_t FDUtils::ReadFromBlocking(int fd, void* buffer, size_t count) {
 #ifdef DEBUG
   bool is_blocking = false;
   ASSERT(FDUtils::IsBlocking(fd, &is_blocking));
   ASSERT(is_blocking);
 #endif
   size_t remaining = count;
@@ skipping 38 matching lines @@
       ASSERT(errno != EWOULDBLOCK);
       return -1;
     } else {
       ASSERT(bytes_written > 0);
       remaining -= bytes_written;
       buffer_pos += bytes_written;
     }
   }
   return count;
 }