[binutils-gdb] Avoid find_thread_ptid with null_ptid

[Pedro Alves <palves at sourceware dot org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=151bb4a5059e73934f7bc61318efaaffe0c91b81

commit 151bb4a5059e73934f7bc61318efaaffe0c91b81
Author: Pedro Alves <palves@redhat.com>
Date:   Thu Nov 22 16:09:12 2018 +0000

    Avoid find_thread_ptid with null_ptid
    
    With a following patch, find_thread_ptid will first find the inferior
    for the passed-in ptid, using find_inferior_pid, and then look for the
    thread in that inferior's thread list.  If we pass down null_ptid to
    find_thread_ptid then that means we'll end up passing 0 to
    find_inferior_pid, which hits this assertion:
    
    >   struct inferior *
    >   find_inferior_pid (int pid)
    >   {
    >     struct inferior *inf;
    >
    >     /* Looking for inferior pid == 0 is always wrong, and indicative of
    >	a bug somewhere else.  There may be more than one with pid == 0,
    >	for instance.  */
    >     gdb_assert (pid != 0);
    
    This patch prepares for the change, by avoiding passing down null_ptid
    to find_thread_ptid or to functions that naturally use it, such as the
    target_pid_to_str call in inferior.c:add_inferior.  In that latter
    case, the patch changes GDB output,
    
    from:
     (gdb) add-inferior
     [New inferior 2 (process 0)]
    
    to:
     (gdb) add-inferior
     [New inferior 2]
    
    which seems like a good change to me.  It might not even make sense to
    talk about "process" for the current target, for example.
    
    The python_on_normal_stop change ends up avoiding looking up the
    same thread twice (inferior_thread also does a look up).
    
    gdb/ChangeLog:
    2018-11-22  Pedro Alves  <palves@redhat.com>
    
    	* cli/cli-interp.c (cli_on_user_selected_context_changed): Use
    	inferior_thread instead of find_thread_ptid, and only when
    	inferior_ptid is not null_ptid.
    	* inferior.c (add_inferior): Don't include target_pid_to_str
    	output when the inferior is not started.
    	* python/py-inferior.c (python_on_normal_stop): Don't use
    	find_thread_ptid.
    	(tui_on_user_selected_context_changed): Use inferior_thread
    	instead of find_thread_ptid, and only when inferior_ptid is not
    	null_ptid.

Diff:
---
 gdb/ChangeLog            | 13 +++++++++++++
 gdb/cli/cli-interp.c     |  4 +---
 gdb/inferior.c           | 11 ++++++++---
 gdb/python/py-inferior.c |  4 ++--
 gdb/tui/tui-interp.c     |  4 +---
 5 files changed, 25 insertions(+), 11 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index d562a4b..a6738bd 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,16 @@
+2018-11-22  Pedro Alves  <palves@redhat.com>
+
+	* cli/cli-interp.c (cli_on_user_selected_context_changed): Use
+	inferior_thread instead of find_thread_ptid, and only when
+	inferior_ptid is not null_ptid.
+	* inferior.c (add_inferior): Don't include target_pid_to_str
+	output when the inferior is not started.
+	* python/py-inferior.c (python_on_normal_stop): Don't use
+	find_thread_ptid.
+	(tui_on_user_selected_context_changed): Use inferior_thread
+	instead of find_thread_ptid, and only when inferior_ptid is not
+	null_ptid.
+
 2018-11-21  Benno Fünfstück  <benno.fuenfstueck@gmail.com>
 
 	PR python/23714
diff --git a/gdb/cli/cli-interp.c b/gdb/cli/cli-interp.c
index 75d8093..b527fc7 100644
--- a/gdb/cli/cli-interp.c
+++ b/gdb/cli/cli-interp.c
@@ -257,13 +257,11 @@ cli_on_command_error (void)
 static void
 cli_on_user_selected_context_changed (user_selected_what selection)
 {
-  struct thread_info *tp;
-
   /* This event is suppressed.  */
   if (cli_suppress_notification.user_selected_context)
     return;
 
-  tp = find_thread_ptid (inferior_ptid);
+  thread_info *tp = inferior_ptid != null_ptid ? inferior_thread () : NULL;
 
   SWITCH_THRU_ALL_UIS ()
     {
diff --git a/gdb/inferior.c b/gdb/inferior.c
index 17d28c4..394386a 100644
--- a/gdb/inferior.c
+++ b/gdb/inferior.c
@@ -122,9 +122,14 @@ add_inferior (int pid)
   struct inferior *inf = add_inferior_silent (pid);
 
   if (print_inferior_events)
-    printf_unfiltered (_("[New inferior %d (%s)]\n"),
-		       inf->num,
-		       target_pid_to_str (ptid_t (pid)));
+    {
+      if (pid != 0)
+	printf_unfiltered (_("[New inferior %d (%s)]\n"),
+			   inf->num,
+			   target_pid_to_str (ptid_t (pid)));
+      else
+	printf_unfiltered (_("[New inferior %d]\n"), inf->num);
+    }
 
   return inf;
 }
diff --git a/gdb/python/py-inferior.c b/gdb/python/py-inferior.c
index e987cfe..7b378ca 100644
--- a/gdb/python/py-inferior.c
+++ b/gdb/python/py-inferior.c
@@ -86,8 +86,8 @@ python_on_normal_stop (struct bpstats *bs, int print_frame)
   if (!gdb_python_initialized)
     return;
 
-  if (!find_thread_ptid (inferior_ptid))
-      return;
+  if (inferior_ptid == null_ptid)
+    return;
 
   stop_signal = inferior_thread ()->suspend.stop_signal;
 
diff --git a/gdb/tui/tui-interp.c b/gdb/tui/tui-interp.c
index acc8f03..a4f3925 100644
--- a/gdb/tui/tui-interp.c
+++ b/gdb/tui/tui-interp.c
@@ -210,13 +210,11 @@ tui_on_command_error (void)
 static void
 tui_on_user_selected_context_changed (user_selected_what selection)
 {
-  struct thread_info *tp;
-
   /* This event is suppressed.  */
   if (cli_suppress_notification.user_selected_context)
     return;
 
-  tp = find_thread_ptid (inferior_ptid);
+  thread_info *tp = inferior_ptid != null_ptid ? inferior_thread () : NULL;
 
   SWITCH_THRU_ALL_UIS ()
     {