gdb: change frame_info::prev_func::p type to cached_copy_status

One might think that variable `frame_info::prev_func::p` is a simple
true/false value, but that's not the case, it can also have the value -1
to mean "unavaiable".  Change it to use the `cached_copy_status` enum,
which seems designed exactly for this purpose.

Rename to `status` to be consistent with `prev_pc::status` (and be cause
`p` means `predicate`, which implies boolean, which this is not).

gdb/ChangeLog:

	* frame.c (frame_info) <prev_func> <p>: Rename to status, change
	type to cached_copy_status.
	(fprintf_frame): Adjust.
	(get_frame_func_if_available): Adjust.
	(frame_cleanup_after_sniffer): Adjust.

Change-Id: I50c6ebef6c0acb076e25c741f7f417bfd101d953

2 files changed, 18 insertions, 8 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index b18627c..da1f2e1 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,11 @@
+2020-08-04  Simon Marchi  <simon.marchi@efficios.com>
+
+	* frame.c (frame_info) <prev_func> <p>: Rename to status, change
+	type to cached_copy_status.
+	(fprintf_frame): Adjust.
+	(get_frame_func_if_available): Adjust.
+	(frame_cleanup_after_sniffer): Adjust.
+
 2020-08-04  Mark Wielaard  <mark@klomp.org>
 
 	* MAINTAINERS (Write After Approval): Update email address.
diff --git a/gdb/frame.c b/gdb/frame.c
index a3599e8..9c3a1ae 100644
--- a/gdb/frame.c
+++ b/gdb/frame.c
@@ -133,7 +133,7 @@ struct frame_info
 
   /* Cached copy of the previous frame's resume address.  */
   struct {
-    enum cached_copy_status status;
+    cached_copy_status status;
     /* Did VALUE require unmasking when being read.  */
     bool masked;
     CORE_ADDR value;
@@ -143,7 +143,7 @@ struct frame_info
   struct
   {
     CORE_ADDR addr;
-    int p;
+    cached_copy_status status;
   } prev_func;
   
   /* This frame's ID.  */
@@ -478,7 +478,7 @@ fprint_frame (struct ui_file *file, struct frame_info *fi)
     fprintf_unfiltered (file, "<unknown>");
   fprintf_unfiltered (file, ",");
   fprintf_unfiltered (file, "func=");
-  if (fi->next != NULL && fi->next->prev_func.p)
+  if (fi->next != NULL && fi->next->prev_func.status == CC_VALUE)
     fprintf_unfiltered (file, "%s", hex_string (fi->next->prev_func.addr));
   else
     fprintf_unfiltered (file, "<unknown>");
@@ -1008,7 +1008,7 @@ get_frame_func_if_available (struct frame_info *this_frame, CORE_ADDR *pc)
 {
   struct frame_info *next_frame = this_frame->next;
 
-  if (!next_frame->prev_func.p)
+  if (next_frame->prev_func.status == CC_UNKNOWN)
     {
       CORE_ADDR addr_in_block;
 
@@ -1016,7 +1016,7 @@ get_frame_func_if_available (struct frame_info *this_frame, CORE_ADDR *pc)
          found.  */
       if (!get_frame_address_in_block_if_available (this_frame, &addr_in_block))
 	{
-	  next_frame->prev_func.p = -1;
+	  next_frame->prev_func.status = CC_UNAVAILABLE;
 	  if (frame_debug)
 	    fprintf_unfiltered (gdb_stdlog,
 				"{ get_frame_func (this_frame=%d)"
@@ -1025,7 +1025,7 @@ get_frame_func_if_available (struct frame_info *this_frame, CORE_ADDR *pc)
 	}
       else
 	{
-	  next_frame->prev_func.p = 1;
+	  next_frame->prev_func.status = CC_VALUE;
 	  next_frame->prev_func.addr = get_pc_function_start (addr_in_block);
 	  if (frame_debug)
 	    fprintf_unfiltered (gdb_stdlog,
@@ -1035,13 +1035,15 @@ get_frame_func_if_available (struct frame_info *this_frame, CORE_ADDR *pc)
 	}
     }
 
-  if (next_frame->prev_func.p < 0)
+  if (next_frame->prev_func.status == CC_UNAVAILABLE)
     {
       *pc = -1;
       return 0;
     }
   else
     {
+      gdb_assert (next_frame->prev_func.status == CC_VALUE);
+
       *pc = next_frame->prev_func.addr;
       return 1;
     }
@@ -2908,7 +2910,7 @@ frame_cleanup_after_sniffer (struct frame_info *frame)
 
      The previous PC is independent of the unwinder, but the previous
      function is not (see get_frame_address_in_block).  */
-  frame->prev_func.p = 0;
+  frame->prev_func.status = CC_UNKNOWN;
   frame->prev_func.addr = 0;
 
   /* Discard the unwinder last, so that we can easily find it if an assertion