gdb: throw OPTIMIZED_OUT_ERROR rather than GENERIC_ERROR

While reviewing this patch:

  https://sourceware.org/pipermail/gdb-patches/2021-November/183227.html

I spotted that the patch could be improved if we threw
OPTIMIZED_OUT_ERROR rather than GENERIC_ERROR in a few places.

This commit updates error_value_optimized_out and
require_not_optimized_out to throw OPTIMIZED_OUT_ERROR.

I ran the testsuite and saw no regressions.  This doesn't really
surprise me, we don't usually write code like:

  catch (const gdb_exception_error &ex)
    {
      (if ex.error == GENERIC_ERROR)
        ...
      else
        ...
    }

There are a three places where we write something like:

  catch (const gdb_exception_error &ex)
    {
      (if ex.error == OPTIMIZED_OUT_ERROR)
        ...
    }

In frame.c:unwind_pc, stack.c:info_frame_command_core, and
value.c:value_optimized_out, but if we are hitting these cases then
it's not significantly changing GDB's behaviour.

1 files changed, 3 insertions, 2 deletions

diff --git a/gdb/value.c b/gdb/value.c
index 998bec3..10edf3b 100644
--- a/gdb/value.c
+++ b/gdb/value.c
@@ -1221,7 +1221,7 @@ value_actual_type (struct value *value, int resolve_simple_types,
 void
 error_value_optimized_out (void)
 {
-  error (_("value has been optimized out"));
+  throw_error (OPTIMIZED_OUT_ERROR, _("value has been optimized out"));
 }
 
 static void
@@ -1230,7 +1230,8 @@ require_not_optimized_out (const struct value *value)
   if (!value->optimized_out.empty ())
     {
       if (value->lval == lval_register)
-	error (_("register has not been saved in frame"));
+	throw_error (OPTIMIZED_OUT_ERROR,
+		     _("register has not been saved in frame"));
       else
 	error_value_optimized_out ();
     }