diff --git a/gdb/ada-tasks.c b/gdb/ada-tasks.c
index 9c07f0ca226..d5ec855f69d 100644
--- a/gdb/ada-tasks.c
+++ b/gdb/ada-tasks.c
@@ -1089,7 +1089,8 @@ print_ada_task_info (struct ui_out *uiout,
       uiout->field_int ("id", taskno);
 
       /* Print the Task ID.  */
-      uiout->field_fmt ("task-id", "%9lx", (long) task_info->task_id);
+      uiout->field_string ("task-id",
+			   hex_string_custom (task_info->task_id, 9));
 
       /* Print the associated Thread ID.  */
       if (uiout->is_mi_like_p ())
@@ -1129,10 +1130,9 @@ print_ada_task_info (struct ui_out *uiout,
 	uiout->field_string ("state", task_states[task_info->state]);
 
       /* Finally, print the task name.  */
-      uiout->field_fmt ("name",
-			"%s",
-			task_info->name[0] != '\0' ? task_info->name
-						   : _("<no name>"));
+      uiout->field_string ("name",
+			   task_info->name[0] != '\0' ? task_info->name
+			   : _("<no name>"));
 
       uiout->text ("\n");
     }
diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
index 8422db8b571..5cdebddfc5d 100644
--- a/gdb/breakpoint.c
+++ b/gdb/breakpoint.c
@@ -4490,13 +4490,13 @@ maybe_print_thread_hit_breakpoint (struct ui_out *uiout)
       struct thread_info *thr = inferior_thread ();
 
       uiout->text ("Thread ");
-      uiout->field_fmt ("thread-id", "%s", print_thread_id (thr));
+      uiout->field_string ("thread-id", print_thread_id (thr));
 
       name = thr->name != NULL ? thr->name : target_thread_name (thr);
       if (name != NULL)
 	{
 	  uiout->text (" \"");
-	  uiout->field_fmt ("name", "%s", name);
+	  uiout->field_string ("name", name);
 	  uiout->text ("\"");
 	}
 
diff --git a/gdb/i386-tdep.c b/gdb/i386-tdep.c
index 00c1f8d7499..42fb8b26463 100644
--- a/gdb/i386-tdep.c
+++ b/gdb/i386-tdep.c
@@ -8914,7 +8914,7 @@ i386_mpx_print_bounds (const CORE_ADDR bt_entry[4])
 
       size = (size > -1 ? size + 1 : size);
       uiout->text (", size = ");
-      uiout->field_fmt ("size", "%s", plongest (size));
+      uiout->field_string ("size", plongest (size));
 
       uiout->text (", metadata = ");
       uiout->field_core_addr ("metadata", gdbarch, bt_entry[3]);
diff --git a/gdb/infrun.c b/gdb/infrun.c
index 4fd92f1bac2..f1f10fd30ff 100644
--- a/gdb/infrun.c
+++ b/gdb/infrun.c
@@ -7690,13 +7690,13 @@ print_signal_received_reason (struct ui_out *uiout, enum gdb_signal siggnal)
       const char *name;
 
       uiout->text ("\nThread ");
-      uiout->field_fmt ("thread-id", "%s", print_thread_id (thr));
+      uiout->field_string ("thread-id", print_thread_id (thr));
 
       name = thr->name != NULL ? thr->name : target_thread_name (thr);
       if (name != NULL)
 	{
 	  uiout->text (" \"");
-	  uiout->field_fmt ("name", "%s", name);
+	  uiout->field_string ("name", name);
 	  uiout->text ("\"");
 	}
     }
diff --git a/gdb/mi/mi-interp.c b/gdb/mi/mi-interp.c
index ad1a06cae0b..76583ff494b 100644
--- a/gdb/mi/mi-interp.c
+++ b/gdb/mi/mi-interp.c
@@ -1172,7 +1172,7 @@ mi_memory_changed (struct inferior *inferior, CORE_ADDR memaddr,
 
       mi_uiout->field_fmt ("thread-group", "i%d", inferior->num);
       mi_uiout->field_core_addr ("addr", target_gdbarch (), memaddr);
-      mi_uiout->field_fmt ("len", "%s", hex_string (len));
+      mi_uiout->field_string ("len", hex_string (len));
 
       /* Append 'type=code' into notification if MEMADDR falls in the range of
 	 sections contain code.  */
diff --git a/gdb/mi/mi-main.c b/gdb/mi/mi-main.c
index 13c310d494c..dc4feedb6f4 100644
--- a/gdb/mi/mi-main.c
+++ b/gdb/mi/mi-main.c
@@ -746,7 +746,7 @@ list_available_thread_groups (const std::set<int> &ids, int recurse)
 
       ui_out_emit_tuple tuple_emitter (uiout, NULL);
 
-      uiout->field_fmt ("id", "%s", pid->c_str ());
+      uiout->field_string ("id", pid->c_str ());
       uiout->field_string ("type", "process");
       if (cmd)
 	uiout->field_string ("description", cmd->c_str ());
diff --git a/gdb/spu-tdep.c b/gdb/spu-tdep.c
index a2ac3149d4d..95303fc7e8f 100644
--- a/gdb/spu-tdep.c
+++ b/gdb/spu-tdep.c
@@ -2096,10 +2096,12 @@ info_spu_event_command (const char *args, int from_tty)
   ui_out_emit_tuple tuple_emitter (current_uiout, "SPUInfoEvent");
 
   current_uiout->text (_("Event Status "));
-  current_uiout->field_fmt ("event_status", "0x%s", phex (event_status, 4));
+  current_uiout->field_string ("event_status",
+			       hex_string_custom (event_status, 4));
   current_uiout->text ("\n");
   current_uiout->text (_("Event Mask   "));
-  current_uiout->field_fmt ("event_mask", "0x%s", phex (event_mask, 4));
+  current_uiout->field_string ("event_mask",
+			       hex_string_custom (event_mask, 4));
   current_uiout->text ("\n");
 }
 
@@ -2168,10 +2170,12 @@ info_spu_signal_command (const char *args, int from_tty)
   if (current_uiout->is_mi_like_p ())
     {
       current_uiout->field_int ("signal1_pending", signal1_pending);
-      current_uiout->field_fmt ("signal1", "0x%s", phex_nz (signal1, 4));
+      current_uiout->field_string ("signal1",
+				   hex_string_custom (signal1, 4));
       current_uiout->field_int ("signal1_type", signal1_type);
       current_uiout->field_int ("signal2_pending", signal2_pending);
-      current_uiout->field_fmt ("signal2", "0x%s", phex_nz (signal2, 4));
+      current_uiout->field_string ("signal2",
+				   hex_string_custom (signal2, 4));
       current_uiout->field_int ("signal2_type", signal2_type);
     }
   else
@@ -2218,7 +2222,7 @@ info_spu_mailbox_list (gdb_byte *buf, int nr, enum bfd_endian byte_order,
 	ULONGEST val;
 	ui_out_emit_tuple tuple_emitter (current_uiout, "mbox");
 	val = extract_unsigned_integer (buf + 4*i, 4, byte_order);
-	current_uiout->field_fmt (field, "0x%s", phex (val, 4));
+	current_uiout->field_string (field, hex_string_custom (val, 4));
       }
 
       current_uiout->text ("\n");
@@ -2421,20 +2425,26 @@ info_spu_dma_cmdlist (gdb_byte *buf, int nr, enum bfd_endian byte_order)
 	current_uiout->field_int ("rid", rclass_id);
 
 	if (ea_valid_p)
-	  current_uiout->field_fmt ("ea", "0x%s", phex (mfc_ea, 8));
+	  current_uiout->field_string ("ea", phex (mfc_ea, 8));
 	else
 	  current_uiout->field_skip ("ea");
 
-	current_uiout->field_fmt ("lsa", "0x%05x", mfc_lsa << 4);
+	current_uiout->field_string ("lsa",
+				     hex_string_custom (mfc_lsa << 4, 5));
 	if (qw_valid_p)
-	  current_uiout->field_fmt ("size", "0x%05x", mfc_size << 4);
+	  current_uiout->field_string ("size",
+				       hex_string_custom (mfc_size << 4, 5));
 	else
-	  current_uiout->field_fmt ("size", "0x%05x", mfc_size);
+	  current_uiout->field_string ("size",
+				       hex_string_custom (mfc_size, 5));
 
 	if (list_valid_p)
 	  {
-	    current_uiout->field_fmt ("lstaddr", "0x%05x", list_lsa << 3);
-	    current_uiout->field_fmt ("lstsize", "0x%05x", list_size << 3);
+	    current_uiout->field_string ("lstaddr",
+					 hex_string_custom (list_lsa << 3, 5));
+	    current_uiout->field_string ("lstsize",
+					 hex_string_custom (list_size << 3,
+							    5));
 	  }
 	else
 	  {
@@ -2494,16 +2504,18 @@ info_spu_dma_command (const char *args, int from_tty)
 
   if (current_uiout->is_mi_like_p ())
     {
-      current_uiout->field_fmt ("dma_info_type", "0x%s",
-				phex_nz (dma_info_type, 4));
-      current_uiout->field_fmt ("dma_info_mask", "0x%s",
-				phex_nz (dma_info_mask, 4));
-      current_uiout->field_fmt ("dma_info_status", "0x%s",
-				phex_nz (dma_info_status, 4));
-      current_uiout->field_fmt ("dma_info_stall_and_notify", "0x%s",
-				phex_nz (dma_info_stall_and_notify, 4));
-      current_uiout->field_fmt ("dma_info_atomic_command_status", "0x%s",
-				phex_nz (dma_info_atomic_command_status, 4));
+      current_uiout->field_string ("dma_info_type",
+				   hex_string_custom (dma_info_type, 4));
+      current_uiout->field_string ("dma_info_mask",
+				   hex_string_custom (dma_info_mask, 4));
+      current_uiout->field_string ("dma_info_status",
+				   hex_string_custom (dma_info_status, 4));
+      current_uiout->field_string
+	("dma_info_stall_and_notify",
+	 hex_string_custom (dma_info_stall_and_notify, 4));
+      current_uiout->field_string
+	("dma_info_atomic_command_status",
+	 hex_string_custom (dma_info_atomic_command_status, 4));
     }
   else
     {
@@ -2564,12 +2576,12 @@ info_spu_proxydma_command (const char *args, int from_tty)
 
   if (current_uiout->is_mi_like_p ())
     {
-      current_uiout->field_fmt ("proxydma_info_type", "0x%s",
-				phex_nz (dma_info_type, 4));
-      current_uiout->field_fmt ("proxydma_info_mask", "0x%s",
-				phex_nz (dma_info_mask, 4));
-      current_uiout->field_fmt ("proxydma_info_status", "0x%s",
-				phex_nz (dma_info_status, 4));
+      current_uiout->field_string ("proxydma_info_type",
+				   hex_string_custom (dma_info_type, 4));
+      current_uiout->field_string ("proxydma_info_mask",
+				   hex_string_custom (dma_info_mask, 4));
+      current_uiout->field_string ("proxydma_info_status",
+				   hex_string_custom (dma_info_status, 4));
     }
   else
     {
@@ -2584,9 +2596,9 @@ info_spu_proxydma_command (const char *args, int from_tty)
 	}
 
       printf_filtered (_("Tag-Group Status  0x%s\n"),
-		       phex (dma_info_status, 4));
+		       hex_string_custom (dma_info_status, 4));
       printf_filtered (_("Tag-Group Mask    0x%s (%s)\n"),
-		       phex (dma_info_mask, 4), query_msg);
+		       hex_string_custom (dma_info_mask, 4), query_msg);
       printf_filtered ("\n");
     }
 
diff --git a/gdb/target.c b/gdb/target.c
index febb3390339..417b795d47f 100644
--- a/gdb/target.c
+++ b/gdb/target.c
@@ -3795,7 +3795,7 @@ flash_erase_command (const char *cmd, int from_tty)
           current_uiout->message (_("Erasing flash memory region at address "));
           current_uiout->field_core_addr ("address", gdbarch, m.lo);
           current_uiout->message (", size = ");
-          current_uiout->field_fmt ("size", "%s", hex_string (m.hi - m.lo));
+          current_uiout->field_string ("size", hex_string (m.hi - m.lo));
           current_uiout->message ("\n");
         }
     }
