* fports.c (scm_fdes_to_port): call fcntl F_GETFL to test that

the fdes is valid before doing anything else.  check that
	the file descriptor supports the modes required.
	(scm_fport_buffer_add): don't throw an error if fstat doesn't
	work: just use the default buffer size.

	* throw.c: change an outdated comment about scm_internal_catch
	BODY: it doesn't take a jumpbuf arg.

	* init.c (scm_standard_stream_to_port): install a handler in case
	scm_fdes_to_port throws an error.  don't check here whether the
	file descriptor is valid, since scm_fdes_to_port will do that.
	set the revealed count depending on whether the port got the
	standard file descriptor.
	(stream_body_data): new type.
	(stream_body, stream_handler): new procs.

libguile/fports.c

@@ -67,6 +67,9 @@ scm_sizet fwrite ();
 
 #include "iselect.h"
 
+/* default buffer size, used if the O/S won't supply a value.  */
+static const int default_buffer_size = 1024;
+
 /* create FPORT buffer with specified sizes (or -1 to use default size or
    0 for no buffer.  */
 static void
@@ -82,11 +85,10 @@ scm_fport_buffer_add (SCM port, int read_size, int write_size)
 #ifdef HAVE_ST_BLKSIZE
       struct stat st;
       
-      if (fstat (fp->fdes, &st) == -1)
-	scm_syserror (s_scm_fport_buffer_add);
-      default_size = st.st_blksize;
+      default_size = (fstat (fp->fdes, &st) == -1) ? default_buffer_size
+	: st.st_blksize;
 #else
-      default_size = 1024;
+      default_size = default_buffer_size;
 #endif
       if (read_size == -1)
 	read_size = default_size;
@@ -359,14 +361,28 @@ SCM_DEFINE (scm_open_file, "open-file", 2, 0, 0,
 /* Build a Scheme port from an open file descriptor `fdes'.
    MODE indicates whether FILE is open for reading or writing; it uses
       the same notation as open-file's second argument.
-   Use NAME as the port's filename.  */
-
+   NAME is a string to be used as the port's filename.
+*/
 SCM
 scm_fdes_to_port (int fdes, char *mode, SCM name)
+#define FUNC_NAME "scm_fdes_to_port"
 {
   long mode_bits = scm_mode_bits (mode);
   SCM port;
   scm_port *pt;
+  int flags;
+
+  /* test that fdes is valid.  */
+  flags = fcntl (fdes, F_GETFL, 0);
+  if (flags == -1)
+    SCM_SYSERROR;
+  flags &= O_ACCMODE;
+  if (flags != O_RDWR
+      && ((flags != O_WRONLY && (mode_bits & SCM_WRTNG))
+	  || (flags != O_RDONLY && (mode_bits & SCM_RDNG))))
+    {
+      SCM_MISC_ERROR ("requested file mode not available on fdes", SCM_EOL);
+    }
 
   SCM_NEWCELL (port);
   SCM_DEFER_INTS;
@@ -378,7 +394,7 @@ scm_fdes_to_port (int fdes, char *mode, SCM name)
     struct scm_fport *fp
       = (struct scm_fport *) malloc (sizeof (struct scm_fport));
     if (fp == NULL)
-      scm_memory_error ("scm_fdes_to_port");
+      SCM_MEMORY_ERROR;
     fp->fdes = fdes;
     pt->rw_random = SCM_FDES_RANDOM_P (fdes);
     SCM_SETSTREAM (port, fp);
@@ -391,7 +407,7 @@ scm_fdes_to_port (int fdes, char *mode, SCM name)
   SCM_ALLOW_INTS;
   return port;
 }
-
+#undef FUNC_NAME
 
 /* Return a lower bound on the number of bytes available for input.  */
 static int

libguile/init.c

@@ -248,32 +248,69 @@ check_config (void)
 
 /* initializing standard and current I/O ports */
 
-/* Like scm_fdes_to_port, except that:
-   - NAME is a standard C string, not a Guile string
-   - we set the revealed count for FILE's file descriptor to 1, so
-     that FDES won't be closed when the port object is GC'd.
-   - when FDES is not a valid file descripter (as determined by
-     fstat), we open "/dev/null" and use that instead.  In that case,
-     the revealed count is left at zero.
-*/
+typedef struct
+{
+  int fdes;
+  char *mode;
+  char *name;
+} stream_body_data;
+
+/* proc to be called in scope of exception handler stream_handler. */
+static SCM
+stream_body (void *data)
+{
+  stream_body_data *body_data = (stream_body_data *) data;
+  SCM port = scm_fdes_to_port (body_data->fdes, body_data->mode,
+			       scm_makfrom0str (body_data->name));
+
+  SCM_REVEALED (port) = 1;
+  return port;
+}
+
+/* exception handler for stream_body.  */
+static SCM
+stream_handler (void *data, SCM tag, SCM throw_args)
+{
+  return SCM_BOOL_F;
+}
+
+/* Convert a file descriptor to a port, using scm_fdes_to_port.
+   - NAME is a C string, not a Guile string
+   - set the revealed count for FILE's file descriptor to 1, so
+   that fdes won't be closed when the port object is GC'd.
+   - catch exceptions: allow Guile to be able to start up even
+   if it has been handed bogus stdin/stdout/stderr.  In this case
+   try to open a new stream on /dev/null.  */
 static SCM
 scm_standard_stream_to_port (int fdes, char *mode, char *name)
 {
-  struct stat st;
-  if (fstat (fdes, &st) == -1)
-    {
-      /* We do not bother to check errno.  When fstat fails, there is
-         generally no point in trying to use FDES, I think. */
+  SCM port;
+  stream_body_data body_data;
 
-      fdes = open ("/dev/null", (mode[0] == 'r')? O_RDONLY : O_WRONLY);
-      return scm_fdes_to_port (fdes, mode, scm_makfrom0str (name));
-    }
-  else
+  body_data.fdes = fdes;
+  body_data.mode = mode;
+  body_data.name = name;
+  port = scm_internal_catch (SCM_BOOL_T, stream_body, &body_data, 
+			     stream_handler, NULL);
+  if (SCM_FALSEP (port))
     {
-      SCM port = scm_fdes_to_port (fdes, mode, scm_makfrom0str (name));
-      scm_set_port_revealed_x (port, SCM_MAKINUM (1));
-      return port;
-    }
+      /* FIXME: /dev/null portability.  there's also *null-device* in
+	 r4rs.scm.  */
+      int null_fdes = open ("/dev/null",
+			    (mode[0] == 'r') ? O_RDONLY : O_WRONLY);
+      
+      body_data.fdes = null_fdes;
+      port = (null_fdes == -1) ? SCM_BOOL_F
+	: scm_internal_catch (SCM_BOOL_T, stream_body, &body_data, 
+			      stream_handler, NULL);
+      /* if the standard fdes was not allocated, reset the revealed count
+	 on the grounds that the user doesn't know what it is. */
+      if (SCM_NFALSEP (port) && null_fdes != fdes)
+	SCM_REVEALED (port) = 0;
+      /* if port is still #f, we'll just leave it like that and
+	 an error will be raised on the first attempt to use it.  */
+    }      
+  return port;
 }
 
 /* Create standard ports from stdin, stdout, and stderr.  */

libguile/ioext.c

@@ -448,13 +448,11 @@ SCM_DEFINE (scm_fdopen, "fdopen", 2, 0, 0,
 	    "by @ref{File Ports, open-file}.")
 #define FUNC_NAME s_scm_fdopen
 {
-  SCM port;
-
   SCM_VALIDATE_INUM (1,fdes);
   SCM_VALIDATE_ROSTRING (2,modes);
   SCM_COERCE_SUBSTR (modes);
-  port = scm_fdes_to_port (SCM_INUM (fdes), SCM_ROCHARS (modes), SCM_BOOL_F);
-  return port;
+
+  return scm_fdes_to_port (SCM_INUM (fdes), SCM_ROCHARS (modes), SCM_BOOL_F);
 }
 #undef FUNC_NAME
 

libguile/throw.c

@@ -148,13 +148,11 @@ struct jmp_buf_and_retval	/* use only on the stack, in scm_catch */
 
    BODY is a pointer to a C function which runs the body of the catch;
    this is the code you can throw from.  We call it like this:
-      BODY (BODY_DATA, JMPBUF)
+      BODY (BODY_DATA)
    where:
       BODY_DATA is just the BODY_DATA argument we received; we pass it
 	 through to BODY as its first argument.  The caller can make
 	 BODY_DATA point to anything useful that BODY might need.
-      JMPBUF is the Scheme jmpbuf object corresponding to this catch,
-         which we have just created and initialized.
 
    HANDLER is a pointer to a C function to deal with a throw to TAG,
    should one occur.  We call it like this:
@@ -610,7 +608,6 @@ SCM_DEFINE (scm_throw, "throw", 1, 0, 1,
 }
 #undef FUNC_NAME
 
-
 SCM
 scm_ithrow (SCM key, SCM args, int noreturn)
 {