Fix swallowed "Quit" when inserting breakpoints

If GDB is inserting a breakpoint and you type Ctrl-C at the exact
"right" time, you'll hit a QUIT call in target_read, and the
breakpoint insertion is cancelled.  However, the related TRY/CATCH
code in insert_bp_location does:

 		  CATCH (e, RETURN_MASK_ALL)
 		    {
		      bp_err = e.error;
		      bp_err_message = e.message;
		    }

The problem with that is that a RETURN_QUIT exception has e.error ==
0, which means that further below, in the places that check for error
with:

      if (bp_err != GDB_NO_ERROR)

because GDB_NO_ERROR == 0, GDB continues as if the breakpoint was
inserted succesfully, and resumes the inferior.  Since the breakpoint
wasn't inserted the inferior runs free, out of our control...

Fix this by having insert_bp_location store a copy of the whole
exception instead of just a error/message parts, and then checking
"gdb_exception::reason" instead.

This was exposed by the new gdb.base/bp-cmds-continue-ctrl-c.exp
testcase added later in the series.

gdb/ChangeLog:
2017-11-16  Pedro Alves  <[email protected]>

	* breakpoint.c (insert_bp_location): Replace bp_err and
	bp_err_message locals by a gdb_exception local.

gdb/ChangeLog

@@ -1,3 +1,8 @@
+2017-11-16  Pedro Alves  <[email protected]>
+
+	* breakpoint.c (insert_bp_location): Replace bp_err and
+	bp_err_message locals by a gdb_exception local.
+
 2017-11-16  Pedro Alves  <[email protected]>
 
 	* inflow.c (scoped_ignore_sigttou): New class.

gdb/breakpoint.c

@@ -2458,8 +2458,7 @@ insert_bp_location (struct bp_location *bl,
 		    int *hw_breakpoint_error,
 		    int *hw_bp_error_explained_already)
 {
-  enum errors bp_err = GDB_NO_ERROR;
-  const char *bp_err_message = NULL;
+  gdb_exception bp_excpt = exception_none;
 
   if (!should_be_inserted (bl) || (bl->inserted && !bl->needs_update))
     return 0;
@@ -2568,12 +2567,11 @@ insert_bp_location (struct bp_location *bl,
 
 	      val = bl->owner->ops->insert_location (bl);
 	      if (val)
-		bp_err = GENERIC_ERROR;
+		bp_excpt = gdb_exception {RETURN_ERROR, GENERIC_ERROR};
 	    }
 	  CATCH (e, RETURN_MASK_ALL)
 	    {
-	      bp_err = e.error;
-	      bp_err_message = e.message;
+	      bp_excpt = e;
 	    }
 	  END_CATCH
 	}
@@ -2608,16 +2606,16 @@ insert_bp_location (struct bp_location *bl,
 		      val = target_insert_breakpoint (bl->gdbarch,
 						      &bl->overlay_target_info);
 		      if (val)
-			bp_err = GENERIC_ERROR;
+			bp_excpt
+			  = gdb_exception {RETURN_ERROR, GENERIC_ERROR};
 		    }
 		  CATCH (e, RETURN_MASK_ALL)
 		    {
-		      bp_err = e.error;
-		      bp_err_message = e.message;
+		      bp_excpt = e;
 		    }
 		  END_CATCH
 
-		  if (bp_err != GDB_NO_ERROR)
+		  if (bp_excpt.reason != 0)
 		    fprintf_unfiltered (tmp_error_stream,
 					"Overlay breakpoint %d "
 					"failed: in ROM?\n",
@@ -2634,12 +2632,11 @@ insert_bp_location (struct bp_location *bl,
 
 	          val = bl->owner->ops->insert_location (bl);
 		  if (val)
-		    bp_err = GENERIC_ERROR;
+		    bp_excpt = gdb_exception {RETURN_ERROR, GENERIC_ERROR};
 	        }
 	      CATCH (e, RETURN_MASK_ALL)
 	        {
-		  bp_err = e.error;
-		  bp_err_message = e.message;
+		  bp_excpt = e;
 	        }
 	      END_CATCH
 	    }
@@ -2651,7 +2648,7 @@ insert_bp_location (struct bp_location *bl,
 	    }
 	}
 
-      if (bp_err != GDB_NO_ERROR)
+      if (bp_excpt.reason != 0)
 	{
 	  /* Can't set the breakpoint.  */
 
@@ -2663,7 +2660,9 @@ insert_bp_location (struct bp_location *bl,
 	     breakpoint insertion failed (e.g., the remote target
 	     doesn't define error codes), so we must treat generic
 	     errors as memory errors.  */
-	  if ((bp_err == GENERIC_ERROR || bp_err == MEMORY_ERROR)
+	  if (bp_excpt.reason == RETURN_ERROR
+	      && (bp_excpt.error == GENERIC_ERROR
+		  || bp_excpt.error == MEMORY_ERROR)
 	      && bl->loc_type == bp_loc_software_breakpoint
 	      && (solib_name_from_address (bl->pspace, bl->address)
 		  || shared_objfile_contains_address_p (bl->pspace,
@@ -2691,16 +2690,18 @@ insert_bp_location (struct bp_location *bl,
 	      if (bl->loc_type == bp_loc_hardware_breakpoint)
 		{
 		  *hw_breakpoint_error = 1;
-		  *hw_bp_error_explained_already = bp_err_message != NULL;
+		  *hw_bp_error_explained_already = bp_excpt.message != NULL;
                   fprintf_unfiltered (tmp_error_stream,
                                       "Cannot insert hardware breakpoint %d%s",
-                                      bl->owner->number, bp_err_message ? ":" : ".\n");
-                  if (bp_err_message != NULL)
-                    fprintf_unfiltered (tmp_error_stream, "%s.\n", bp_err_message);
+                                      bl->owner->number,
+				      bp_excpt.message ? ":" : ".\n");
+                  if (bp_excpt.message != NULL)
+                    fprintf_unfiltered (tmp_error_stream, "%s.\n",
+					bp_excpt.message);
 		}
 	      else
 		{
-		  if (bp_err_message == NULL)
+		  if (bp_excpt.message == NULL)
 		    {
 		      std::string message
 			= memory_error_message (TARGET_XFER_E_IO,
@@ -2716,7 +2717,7 @@ insert_bp_location (struct bp_location *bl,
 		      fprintf_unfiltered (tmp_error_stream,
 					  "Cannot insert breakpoint %d: %s\n",
 					  bl->owner->number,
-					  bp_err_message);
+					  bp_excpt.message);
 		    }
 		}
 	      return 1;