"target remote | " stderr

[Vladimir Prus <vladimir at codesourcery dot com>]

At the moment, when handling

	target remote | whatever

gdb does not do anything with 'whatever''s stderr. This is not good,
because when using MI, frontend might not even look at stderr at all,
so messages from 'whatever' get lost.

This patch fixes that. The fix is only for Linux, I plan to do the
same with mingw support, but only if this patch is considered OK.

- Volodya

	Pass stderr of program run with "target remote |"
	via gdb_stderr.
	* serial.c (serial_open): Set error_fd to -1.
	* serial.h (struct serial): New field error_fd.
	* ser-pipe.c (pipe_open): Create another pair
	of sockets.  Pass stderr to gdb.
	* ser-base.c (generic_readchar): Check if there's
	anything in stderr channel and route that to gdb_stderr.

--- gdb/serial.c	(/mirrors/gdb_mainline)	(revision 3222)
+++ gdb/serial.c	(/patches/gdb/remote_stderr/gdb_mainline)	(revision 3222)
@@ -211,6 +211,7 @@ serial_open (const char *name)
 
   scb->bufcnt = 0;
   scb->bufp = scb->buf;
+  scb->error_fd = -1;
 
   if (scb->ops->open (scb, open_name))
     {
--- gdb/serial.h	(/mirrors/gdb_mainline)	(revision 3222)
+++ gdb/serial.h	(/patches/gdb/remote_stderr/gdb_mainline)	(revision 3222)
@@ -191,6 +191,12 @@ extern int serial_debug_p (struct serial
 struct serial
   {
     int fd;			/* File descriptor */
+    int error_fd;               /* File descriptor for a separate
+				   error stream that should be
+				   immediately forwarded to gdb_stderr.
+				   This may be -1.  
+				   If != -1, this descriptor should
+				   be non-blocking.  */
     struct serial_ops *ops;	/* Function vector */
     void *state;       		/* Local context info for open FD */
     serial_ttystate ttystate;	/* Not used (yet) */
--- gdb/ser-pipe.c	(/mirrors/gdb_mainline)	(revision 3222)
+++ gdb/ser-pipe.c	(/patches/gdb/remote_stderr/gdb_mainline)	(revision 3222)
@@ -62,9 +62,12 @@ pipe_open (struct serial *scb, const cha
    * published in UNIX Review, Vol. 6, No. 8.
    */
   int pdes[2];
+  int err_pdes[2];
   int pid;
   if (socketpair (AF_UNIX, SOCK_STREAM, 0, pdes) < 0)
     return -1;
+  if (socketpair (AF_UNIX, SOCK_STREAM, 0, err_pdes) < 0)
+    return -1;
 
   /* Create the child process to run the command in.  Note that the
      apparent call to vfork() below *might* actually be a call to
@@ -77,9 +80,18 @@ pipe_open (struct serial *scb, const cha
     {
       close (pdes[0]);
       close (pdes[1]);
+      close (err_pdes[0]);
+      close (err_pdes[1]);
       return -1;
     }
 
+  if (fcntl (err_pdes[0], F_SETFL, O_NONBLOCK) == -1)
+    {
+      close (err_pdes[0]);
+      close (err_pdes[1]);
+      err_pdes[0] = err_pdes[1] = -1;
+    }
+
   /* Child. */
   if (pid == 0)
     {
@@ -91,6 +103,13 @@ pipe_open (struct serial *scb, const cha
 	  close (pdes[1]);
 	}
       dup2 (STDOUT_FILENO, STDIN_FILENO);
+
+      if (err_pdes[0] != -1)
+	{
+	  close (err_pdes[0]);
+	  dup2 (err_pdes[1], STDERR_FILENO);
+	  close (err_pdes[1]);
+	}
 #if 0
       /* close any stray FD's - FIXME - how? */
       /* POSIX.2 B.3.2.2 "popen() shall ensure that any streams
@@ -109,6 +128,7 @@ pipe_open (struct serial *scb, const cha
   state = XMALLOC (struct pipe_state);
   state->pid = pid;
   scb->fd = pdes[0];
+  scb->error_fd = err_pdes[0];
   scb->state = state;
 
   /* If we don't do this, GDB simply exits when the remote side dies.  */
--- gdb/ser-base.c	(/mirrors/gdb_mainline)	(revision 3222)
+++ gdb/ser-base.c	(/patches/gdb/remote_stderr/gdb_mainline)	(revision 3222)
@@ -314,6 +314,33 @@ generic_readchar (struct serial *scb, in
 		  int (do_readchar) (struct serial *scb, int timeout))
 {
   int ch;
+
+  /* Read any error output we might have.  */
+  if (scb->error_fd != -1)
+    {
+      ssize_t s;
+      char buf[81];
+      while ((s = read (scb->error_fd, &buf, 80)) > 0)
+	{
+	  char *current;
+	  char *newline;
+	  /* In theory, embedded newlines are not a problem.
+	     But for MI, we want each output line to have just
+	     one newline for legibility.  So output things
+	     in newline chunks.  */
+	  buf[s] = '\0';
+	  current = buf;
+	  while ((newline = strstr (current, "\n")) != NULL)
+	    {
+	      *newline = '\0';
+	      fputs_unfiltered (current, gdb_stderr);
+	      fputs_unfiltered ("\n", gdb_stderr);
+	      current = newline + 1;
+	    }
+	  fputs_unfiltered (current, gdb_stderr);
+	}
+    }
+
   if (scb->bufcnt > 0)
     {
       ch = *scb->bufp;