The last checkin replaced some impossible error handling with DEBUGASSERT. Except that one of the case is actually possible in one cornercase and had to be restored

nuttx/configs/sim/README.txt

@@ -165,6 +165,9 @@ I never did get networking to work on the sim target.  It tries to use the tap d
 (/dev/net/tun) to emulate an Ethernet NIC, but I never got it correctly integrated
 with the NuttX networking (I probably should try using raw sockets instead).
 
+Update:  Max Holtzberg reports to me that the tap device actually does work properly,
+but not in an NSH configuration because of stdio operations freeze the simulation.
+
 X11 Issues
 ----------
 There is an X11-based framebuffer driver that you can use exercise the NuttX graphics

nuttx/fs/fs_lseek.c

@@ -80,7 +80,7 @@ off_t file_seek(FAR struct file *filep, off_t offset, int whence)
   int ret;
   int err = OK;
 
-  DEBUGASSERT(seekfile);
+  DEBUGASSERT(filep);
   inode =  filep->f_inode;
 
   /* Invoke the file seek method if available */
@@ -173,9 +173,6 @@ errout:
 off_t lseek(int fd, off_t offset, int whence)
 {
   FAR struct filelist *list;
-  FAR struct file     *filep;
-  FAR struct inode    *inode;
-  int                  err;
 
   /* Did we get a valid file descriptor? */
 
@@ -184,15 +181,17 @@ off_t lseek(int fd, off_t offset, int whence)
       set_errno(EBADF);
       return (off_t)ERROR;
     }
+  else
+    {
+      /* Get the thread-specific file list */
 
-  /* Get the thread-specific file list */
+      list = sched_getfiles();
+      DEBUGASSERT(list);
 
-  list = sched_getfiles();
-  DEBUGASSERT(list);
+      /* Then let file_seek do the real work */
 
-  /* Then let file_seek do the real work */
-
-  return file_seek(&list->fl_files[fd], offset, whence);
+      return file_seek(&list->fl_files[fd], offset, whence);
+    }
 }
 
 #endif

nuttx/fs/fs_write.c

@@ -67,7 +67,17 @@ static inline ssize_t file_write(int fd, FAR const void *buf, size_t nbytes)
   /* Get the thread-specific file list */
 
   list = sched_getfiles();
-  DEBUGASSERT(list);
+
+  /* The file list can be NULL under one obscure cornercase:  When memory
+   * management debug output is enabled.  Then there may be attempts to
+   * write to stdout from malloc before the group data has been allocated.
+   */
+
+  if (!list)
+    {
+      err = EAGAIN;
+      goto errout;
+    }
 
   /* Was this file opened for write access? */
 

nuttx/include/nuttx/fs/fs.h

@@ -621,7 +621,7 @@ int lib_flushall(FAR struct streamlist *list);
 ssize_t lib_sendfile(int outfd, int infd, off_t *offset, size_t count);
 #endif
 
-/* fs/fs_fileread.c *********************************************************/
+/* fs/fs_read.c *************************************************************/
 /****************************************************************************
  * Name: file_read
  *
@@ -636,7 +636,7 @@ ssize_t lib_sendfile(int outfd, int infd, off_t *offset, size_t count);
 ssize_t file_read(FAR struct file *filep, FAR void *buf, size_t nbytes);
 #endif
 
-/* fs/fs_fileread.c *********************************************************/
+/* fs/fs_lseek.c ************************************************************/
 /****************************************************************************
  * Name: file_seek
  *