[PATCH] Extra error message from update_watchpoint

["Andrew Burgess" <aburgess at broadcom dot com>]

While working on this:
  URL

I found the error message:
  Expression cannot be implemented with read/access watchpoint.

is also issued when hardware watchpoints are turned off, this
error seems a little confusing as the problem is not the
expression, but that software read/access watchpoints is not
supported.

After the patch I've ADDED an extra error message:
  Software read/access watchpoints not supported.

Which will be selected where appropriate.

OK to apply?

Thanks,
Andrew

gdb/ChangeLog

2013-10-18  Andrew Burgess  <aburgess@broadcom.com>

	* breakpoint.c (update_watchpoint): Give a different error message
	when software watchpoints are explicitly turned off.
    
gdb/testsuite/ChangeLog

2013-10-18  Andrew Burgess  <aburgess@broadcom.com>

	* gdb.base/watchpoint.exp: (test_no_hw_watchpoints): Update
	expected results, add additional test.
	(test_watch_register_location): New.
	(do_tests): Call test_watch_register_location.

diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
index c630b87..6e87e22 100644
--- a/gdb/breakpoint.c
+++ b/gdb/breakpoint.c
@@ -1946,8 +1946,13 @@ update_watchpoint (struct watchpoint *b, int reparse)
 		}
 	    }
 	  else if (!b->base.ops->works_in_software_mode (&b->base))
-	    error (_("Expression cannot be implemented with "
-		     "read/access watchpoint."));
+	    {
+	      if (!can_use_hw_watchpoints)
+		error (_("Software read/access watchpoints not supported."));
+	      else
+		error (_("Expression cannot be implemented with "
+			 "read/access watchpoint."));
+	    }
 	  else
 	    b->base.type = bp_watchpoint;
 
diff --git a/gdb/testsuite/gdb.base/watchpoint.exp b/gdb/testsuite/gdb.base/watchpoint.exp
index e0d4f81..5a5f149 100644
--- a/gdb/testsuite/gdb.base/watchpoint.exp
+++ b/gdb/testsuite/gdb.base/watchpoint.exp
@@ -825,8 +825,12 @@ proc test_no_hw_watchpoints {} {
     # refrains from using them.
     #
     gdb_test "rwatch ival3" \
-	"Expression cannot be implemented with read/access watchpoint..*" \
+	"Software read/access watchpoints not supported..*" \
 	"rwatch disallowed when can-set-hw-watchpoints cleared"
+    gdb_test "awatch ival3" \
+	"Software read/access watchpoints not supported..*" \
+	"awatch disallowed when can-set-hw-watchpoints cleared"
+
 
     # Re-enable hardware watchpoints if necessary.
     if ![target_info exists gdb,no_hardware_watchpoints] {
@@ -879,6 +883,22 @@ proc test_watchpoint_in_big_blob {} {
     gdb_test_no_output "delete \$bpnum" "delete watch buf"
 }
 
+proc test_watch_register_location {} {
+    global no_hw
+
+    if {!$no_hw && ![target_info exists gdb,no_hardware_watchpoints]} {
+	# Non-memory read/access watchpoints are not supported, they would
+	# require software read/access watchpoint support (which is not
+	# currently available).
+	gdb_test "rwatch \$pc" \
+	    "Expression cannot be implemented with read/access watchpoint..*" \
+	    "rwatch disallowed for register based expression"
+	gdb_test "awatch \$pc" \
+	    "Expression cannot be implemented with read/access watchpoint..*" \
+	    "awatch disallowed for register based expression"
+    }
+}
+
 # Start with a fresh gdb.
 
 set prev_timeout $timeout
@@ -940,6 +960,8 @@ proc do_tests {} {
 
     test_wide_location_1
     test_wide_location_2
+
+    test_watch_register_location
 }
 
 # On targets that can do hardware watchpoints, run the tests twice: