Re: [RFA] initialize err variable in load_section_callback()

[Daniel Jacobowitz <drow@false.org>]

On Mon, Dec 27, 2004 at 06:33:48PM -0800, Theodore A. Roth wrote:
> This patch got left hanging. Is it a lost cause or can I get approval to
> commit it?

Sorry about the delay; a coworker just ran into this, which prodded me
to take another look at the problem.  I'm committing something similar. 
Your patch isn't quite right... here's the documented behavior
of target_read_memory_partial:

/* Make a single attempt at transfering LEN bytes.  On a successful
   transfer, the number of bytes actually transfered is returned and
   ERR is set to 0.  When a transfer fails, -1 is returned (the number
   of bytes actually transfered is not defined) and ERR is set to a
   non-zero error indication.  */

Here's a bit of target_read_partial:

/* Request the transfer of up to LEN 8-bit bytes of the target's
   OBJECT.  The OFFSET, for a seekable object, specifies the starting
   point.  The ANNEX can be used to provide additional data-specific
   information to the target.

   Return the number of bytes actually transfered, zero when no
   further transfer is possible, and -1 when the transfer is not
   supported.

"No further transfer is possible" is an error condition. 
remote_xfer_partial and inf_ptrace_xfer_partial don't seem to agree
about whether an I/O failure is a "return 0" or a "return -1"
condition; I am inclined to agree with the inf_ptrace implementation,
since the transfer is supported, but failed.  An argument could be made
for either.

This patch makes target_write_memory_partial obey its specification, as
long as target_read_partial obeys its.  No further transfer and
unsupported are both error conditions.  The specifications could still
use some clarifying (separately).

Tested on i686-linux native, and tested by hand that load doesn't blow
up any more.

> > > - when -ve, set *err -VE return value
> >
> > I assume -ve is an error code? Sould I extend my patch to also check for
> > retval < -1 and if so set *err to retval?

He just meant "negative": if the return value is negative, set *err to
its absolute value.  I stuck with the existing use of errno instead.

-- 
Daniel Jacobowitz
CodeSourcery, LLC

2005-03-04  Daniel Jacobowitz  <dan@codesourcery.com>

	* target.c (target_read_memory_partial): Always initialize
	ERR.
	(target_write_memory_partial): Likewise.

Index: target.c
===================================================================
RCS file: /cvs/src/src/gdb/target.c,v
retrieving revision 1.101
diff -u -p -r1.101 target.c
--- target.c	24 Feb 2005 13:51:35 -0000	1.101
+++ target.c	4 Mar 2005 17:08:12 -0000
@@ -1,7 +1,7 @@
 /* Select target systems and architectures at runtime for GDB.
 
    Copyright 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
-   1999, 2000, 2001, 2002, 2003, 2004 Free Software Foundation, Inc.
+   1999, 2000, 2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
 
    Contributed by Cygnus Support.
 
@@ -1249,8 +1249,26 @@ int
 target_read_memory_partial (CORE_ADDR memaddr, char *buf, int len, int *err)
 {
   if (target_xfer_partial_p ())
-    return target_xfer_partial (target_stack, TARGET_OBJECT_MEMORY, NULL,
-				buf, NULL, memaddr, len);
+    {
+      int retval;
+
+      retval = target_xfer_partial (target_stack, TARGET_OBJECT_MEMORY,
+				    NULL, buf, NULL, memaddr, len);
+
+      if (retval <= 0)
+	{
+	  if (errno)
+	    *err = errno;
+	  else
+	    *err = EIO;
+	  return -1;
+	}
+      else
+	{
+	  *err = 0;
+	  return retval;
+	}
+    }
   else
     return target_xfer_memory_partial (memaddr, buf, len, 0, err);
 }
@@ -1259,8 +1277,26 @@ int
 target_write_memory_partial (CORE_ADDR memaddr, char *buf, int len, int *err)
 {
   if (target_xfer_partial_p ())
-    return target_xfer_partial (target_stack, TARGET_OBJECT_MEMORY, NULL,
-				NULL, buf, memaddr, len);
+    {
+      int retval;
+
+      retval = target_xfer_partial (target_stack, TARGET_OBJECT_MEMORY,
+				    NULL, NULL, buf, memaddr, len);
+
+      if (retval <= 0)
+	{
+	  if (errno)
+	    *err = errno;
+	  else
+	    *err = EIO;
+	  return -1;
+	}
+      else
+	{
+	  *err = 0;
+	  return retval;
+	}
+    }
   else
     return target_xfer_memory_partial (memaddr, buf, len, 1, err);
 }