[PATCH] Hardware breakpoint error reporting

Stan Shebs stanshebs@earthlink.net
Wed May 9 17:50:00 GMT 2012


On 5/3/12 9:25 AM, Mike Wrighton wrote:
> Hi,
>
> I've attached a patch to improve error reporting for hardware 
> breakpoint insertion errors on remote targets. Currently the error 
> response coming back over RSP is discarded, and instead the default 
> error:
>
> "... You may have requested too many hardware breakpoints/watchpoints."
>
> is printed, which is often not helpful to users.
>
> Note my copyright assignment is currently in progress.
>

I understand the assignment is now done, which is great!

Conceptually the patch is good, I just have a couple coding quibbles:

@@ -2257,11 +2274,20 @@ insert_bp_location (struct bp_location *bl,
  	    {
  	      if (bl->loc_type == bp_loc_hardware_breakpoint)
  		{
-		  *hw_breakpoint_error = 1;
-		  fprintf_unfiltered (tmp_error_stream,
-				      "Cannot insert hardware "
-				      "breakpoint %d.\n",
-				      bl->owner->number);
+                  if (hw_bp_err_string)
+                    {
+                      *hw_breakpoint_error = 2;
+                      fprintf_unfiltered (tmp_error_stream,
+                                          "Cannot insert hardware breakpoint %d: %s.\n",
+                                          bl->owner->number, hw_bp_err_string);
+                    }
+                  else
+                    {
+                      *hw_breakpoint_error = 1;
+                      fprintf_unfiltered (tmp_error_stream,
+                                          "Cannot insert hardware breakpoint %d.\n",
+                                          bl->owner->number);
+                    }
  		}
  	      else
  		{
@@ -2590,7 +2616,7 @@ insert_breakpoint_locations (void)
      {
        /* If a hardware breakpoint or watchpoint was inserted, add a
           message about possibly exhausted resources.  */
-      if (hw_breakpoint_error)
+      if (hw_breakpoint_error == 1)
  	{
  	  fprintf_unfiltered (tmp_error_stream,
  			      "Could not insert hardware breakpoints:\n\


In general, we'd rather not have obscurely-meaningful integer values running around, and certainly not without documentation in the code.

Thinking about what's really going on here, the lower-level insertion has gotten an explanation of what went wrong, and so you want the higher-level code not to speculate on possibilities that are obviously irrelevant.  So maybe another flag, like "hw_bp_error_explained_already"?  I'd also try to do a single "Cannot insert..." printf, and have the explanation as a second print that is an addendum.


@@ -8131,6 +8133,13 @@ remote_insert_hw_breakpoint (struct gdbarch *gdbarch,
    switch (packet_ok (rs->buf,&remote_protocol_packets[PACKET_Z1]))
      {
      case PACKET_ERROR:
+      if (rs->buf[1] == '.')
+        {
+          message = strchr (rs->buf + 2, '.');
+          if (message)
+            error ("%s", message + 1);


Should have a "Remote failure reply: " at the front of the message, similar to other cases in remote.c; there's no assurance that a bad target won't send back massive line noise as its, ahem, message; so we need the explanatory phrase.

Stan





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