pass NULL to TARGET_DEFAULT_RETURN when appropriate

This changes instances of TARGET_DEFAULT_RETURN(0) to
TARGET_DEFAULT_RETURN(NULL) when appropriate.  The use of "0" was a
relic from an earlier implementation of make-target-delegates; and I
didn't want to go back through the long patch series, fixing up
conflicts, just to change this small detail.

2014-02-19  Tom Tromey  <tromey@redhat.com>

	* target-delegates.c: Rebuild.
	* target.h (struct target_ops) <to_extra_thread_info,
	to_thread_name, to_pid_to_exec_file, to_get_section_table,
	to_memory_map, to_read_description, to_traceframe_info>: Use NULL,
	not 0, in TARGET_DEFAULT_RETURN.

3 files changed, 22 insertions, 14 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 0dd90ca..7496e3b 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,13 @@
 2014-02-19  Tom Tromey  <tromey@redhat.com>
 
+	* target-delegates.c: Rebuild.
+	* target.h (struct target_ops) <to_extra_thread_info,
+	to_thread_name, to_pid_to_exec_file, to_get_section_table,
+	to_memory_map, to_read_description, to_traceframe_info>: Use NULL,
+	not 0, in TARGET_DEFAULT_RETURN.
+
+2014-02-19  Tom Tromey  <tromey@redhat.com>
+
 	* target.c (complete_target_initialization): Remove casts.  Use
 	return_zero_has_execution.
 	(return_zero): Add "ignore" argument.
diff --git a/gdb/target-delegates.c b/gdb/target-delegates.c
index 4585d25..15ab43a 100644
--- a/gdb/target-delegates.c
+++ b/gdb/target-delegates.c
@@ -609,7 +609,7 @@ delegate_extra_thread_info (struct target_ops *self, struct thread_info *arg1)
 static char *
 tdefault_extra_thread_info (struct target_ops *self, struct thread_info *arg1)
 {
-  return 0;
+  return NULL;
 }
 
 static char *
@@ -622,7 +622,7 @@ delegate_thread_name (struct target_ops *self, struct thread_info *arg1)
 static char *
 tdefault_thread_name (struct target_ops *self, struct thread_info *arg1)
 {
-  return 0;
+  return NULL;
 }
 
 static void
@@ -654,7 +654,7 @@ delegate_pid_to_exec_file (struct target_ops *self, int arg1)
 static char *
 tdefault_pid_to_exec_file (struct target_ops *self, int arg1)
 {
-  return 0;
+  return NULL;
 }
 
 static void
@@ -679,7 +679,7 @@ delegate_get_section_table (struct target_ops *self)
 static struct target_section_table *
 tdefault_get_section_table (struct target_ops *self)
 {
-  return 0;
+  return NULL;
 }
 
 static int
@@ -772,7 +772,7 @@ delegate_memory_map (struct target_ops *self)
 static VEC(mem_region_s) *
 tdefault_memory_map (struct target_ops *self)
 {
-  return 0;
+  return NULL;
 }
 
 static void
@@ -811,7 +811,7 @@ delegate_read_description (struct target_ops *self)
 static const struct target_desc *
 tdefault_read_description (struct target_ops *self)
 {
-  return 0;
+  return NULL;
 }
 
 static ptid_t
@@ -1297,7 +1297,7 @@ delegate_traceframe_info (struct target_ops *self)
 static struct traceframe_info *
 tdefault_traceframe_info (struct target_ops *self)
 {
-  return 0;
+  return NULL;
 }
 
 static int
diff --git a/gdb/target.h b/gdb/target.h
index 34539c1..79805d1 100644
--- a/gdb/target.h
+++ b/gdb/target.h
@@ -567,20 +567,20 @@ struct target_ops
     char *(*to_pid_to_str) (struct target_ops *, ptid_t)
       TARGET_DEFAULT_FUNC (default_pid_to_str);
     char *(*to_extra_thread_info) (struct target_ops *, struct thread_info *)
-      TARGET_DEFAULT_RETURN (0);
+      TARGET_DEFAULT_RETURN (NULL);
     char *(*to_thread_name) (struct target_ops *, struct thread_info *)
-      TARGET_DEFAULT_RETURN (0);
+      TARGET_DEFAULT_RETURN (NULL);
     void (*to_stop) (struct target_ops *, ptid_t)
       TARGET_DEFAULT_IGNORE ();
     void (*to_rcmd) (struct target_ops *,
 		     char *command, struct ui_file *output)
       TARGET_DEFAULT_FUNC (default_rcmd);
     char *(*to_pid_to_exec_file) (struct target_ops *, int pid)
-      TARGET_DEFAULT_RETURN (0);
+      TARGET_DEFAULT_RETURN (NULL);
     void (*to_log_command) (struct target_ops *, const char *)
       TARGET_DEFAULT_IGNORE ();
     struct target_section_table *(*to_get_section_table) (struct target_ops *)
-      TARGET_DEFAULT_RETURN (0);
+      TARGET_DEFAULT_RETURN (NULL);
     enum strata to_stratum;
     int (*to_has_all_memory) (struct target_ops *);
     int (*to_has_memory) (struct target_ops *);
@@ -672,7 +672,7 @@ struct target_ops
        change unexpectedly, it should be invalidated, and higher
        layers will re-fetch it.  */
     VEC(mem_region_s) *(*to_memory_map) (struct target_ops *)
-      TARGET_DEFAULT_RETURN (0);
+      TARGET_DEFAULT_RETURN (NULL);
 
     /* Erases the region of flash memory starting at ADDRESS, of
        length LENGTH.
@@ -695,7 +695,7 @@ struct target_ops
        "beneath" target.  Returns the description found, or NULL if no
        description was available.  */
     const struct target_desc *(*to_read_description) (struct target_ops *ops)
-	 TARGET_DEFAULT_RETURN (0);
+	 TARGET_DEFAULT_RETURN (NULL);
 
     /* Build the PTID of the thread on which a given task is running,
        based on LWP and THREAD.  These values are extracted from the
@@ -987,7 +987,7 @@ struct target_ops
        cache data; higher layers take care of caching, invalidating,
        and re-fetching when necessary.  */
     struct traceframe_info *(*to_traceframe_info) (struct target_ops *)
-      TARGET_DEFAULT_RETURN (0);
+      TARGET_DEFAULT_RETURN (NULL);
 
     /* Ask the target to use or not to use agent according to USE.  Return 1
        successful, 0 otherwise.  */