gdb: use -1 for breakpoint::task default value

Within the breakpoint struct we have two fields ::thread and ::task
which are used for thread or task specific breakpoints.  When a
breakpoint doesn't have a specific thread or task then these fields
have the values -1 and 0 respectively.

There's no particular reason (as far as I can tell) why these two
"default" values are different, and I find the difference a little
confusing.  Long term I'd like to potentially fold these two fields
into a single field, but that isn't what this commit does.

What this commit does is switch to using -1 as the "default" value for
both fields, this means that the default for breakpoint::task has
changed from 0 to -1.   I've updated all the code I can find that
relied on the value of 0, and I see no test regressions, especially in
gdb.ada/tasks.exp, which still fully passes.

There should be no user visible changes after this commit.

Approved-By: Pedro Alves <pedro@palves.net>

1 files changed, 3 insertions, 3 deletions

diff --git a/gdb/guile/scm-breakpoint.c b/gdb/guile/scm-breakpoint.c
index d4f2b73..2931df2 100644
--- a/gdb/guile/scm-breakpoint.c
+++ b/gdb/guile/scm-breakpoint.c
@@ -774,7 +774,7 @@ gdbscm_set_breakpoint_thread_x (SCM self, SCM newvalue)
 				     _("invalid thread id"));
 	}
 
-      if (bp_smob->bp->task != 0)
+      if (bp_smob->bp->task != -1)
 	scm_misc_error (FUNC_NAME,
 			_("cannot set both task and thread attributes"),
 			SCM_EOL);
@@ -797,7 +797,7 @@ gdbscm_breakpoint_task (SCM self)
   breakpoint_smob *bp_smob
     = bpscm_get_valid_breakpoint_smob_arg_unsafe (self, SCM_ARG1, FUNC_NAME);
 
-  if (bp_smob->bp->task == 0)
+  if (bp_smob->bp->task == -1)
     return SCM_BOOL_F;
 
   return scm_from_long (bp_smob->bp->task);
@@ -840,7 +840,7 @@ gdbscm_set_breakpoint_task_x (SCM self, SCM newvalue)
 			SCM_EOL);
     }
   else if (gdbscm_is_false (newvalue))
-    id = 0;
+    id = -1;
   else
     SCM_ASSERT_TYPE (0, newvalue, SCM_ARG2, FUNC_NAME, _("integer or #f"));