gdb: add all_objfiles_removed observer

The new_objfile observer is currently used to indicate both when a new
objfile is added to program space (when passed non-nullptr) and when all
objfiles of a program space were just removed (when passed nullptr).
I think this is confusing (and Andrew apparently thinks so too [1]).
Add a new "all_objfiles_removed" observer to remove the second role from
"new_objfile".

Some existing users of new_objfile do nothing if the passed objfile is
nullptr.  For them, we can simply drop the nullptr check.  For others,
add a new all_objfiles_removed callback, and refactor things a bit to
keep the existing behavior as much as possible.

Some callbacks relied on current_program_space, and following
the refactoring now use either objfile->pspace or the pspace passed to
all_objfiles_removed.  I think this should be relatively safe, and in
general a step in the right direction.

On the notify side, I found only one call site to change from
new_objfile to all_objfiles_removed, in clear_symtab_users.  It is not
entirely clear to me that this is entirely correct.  clear_symtab_users
appears to be called in spots that don't remove all objfiles
(functions finish_new_objfile, remove_symbol_file_command, reread_symbols,
do_module_cleanups).  But I think that this patch at least makes the
current code clearer.

[1] https://gitlab.com/gnutools/binutils-gdb/-/commit/a0a031bce0527b1521788b5dad640e7883b3a252

Change-Id: Icb648f72862e056267f30f44dd439bd4ec766f13
Approved-By: Tom Tromey <tom@tromey.com>

16 files changed, 105 insertions, 102 deletions

diff --git a/gdb/ada-lang.c b/gdb/ada-lang.c
index 4dc4055..a37e563 100644
--- a/gdb/ada-lang.c
+++ b/gdb/ada-lang.c
@@ -13884,7 +13884,7 @@ static struct cmd_list_element *show_ada_list;
 static void
 ada_new_objfile_observer (struct objfile *objfile)
 {
-  ada_clear_symbol_cache (current_program_space);
+  ada_clear_symbol_cache (objfile->pspace);
 }
 
 /* This module's 'free_objfile' observer.  */
@@ -13892,7 +13892,7 @@ ada_new_objfile_observer (struct objfile *objfile)
 static void
 ada_free_objfile_observer (struct objfile *objfile)
 {
-  ada_clear_symbol_cache (current_program_space);
+  ada_clear_symbol_cache (objfile->pspace);
 }
 
 /* Charsets known to GNAT.  */
@@ -14025,6 +14025,8 @@ DWARF attribute."),
 
   /* The ada-lang observers.  */
   gdb::observers::new_objfile.attach (ada_new_objfile_observer, "ada-lang");
+  gdb::observers::all_objfiles_removed.attach (ada_clear_symbol_cache,
+					       "ada-lang");
   gdb::observers::free_objfile.attach (ada_free_objfile_observer, "ada-lang");
   gdb::observers::inferior_exit.attach (ada_inferior_exit, "ada-lang");
 
diff --git a/gdb/ada-tasks.c b/gdb/ada-tasks.c
index 14b0bf1..1de6b0f 100644
--- a/gdb/ada-tasks.c
+++ b/gdb/ada-tasks.c
@@ -1469,38 +1469,31 @@ ada_tasks_normal_stop_observer (struct bpstat *unused_args, int unused_args2)
   ada_task_list_changed (current_inferior ());
 }
 
-/* A routine to be called when the objfiles have changed.  */
+/* Clear data associated to PSPACE and all inferiors using that program
+   space.  */
 
 static void
-ada_tasks_new_objfile_observer (struct objfile *objfile)
+ada_tasks_clear_pspace_data (program_space *pspace)
 {
-  /* Invalidate the relevant data in our program-space data.  */
-
-  if (objfile == NULL)
-    {
-      /* All objfiles are being cleared, so we should clear all
-	 our caches for all program spaces.  */
-      for (struct program_space *pspace : program_spaces)
-	ada_tasks_invalidate_pspace_data (pspace);
-    }
-  else
-    {
-      /* The associated program-space data might have changed after
-	 this objfile was added.  Invalidate all cached data.  */
-      ada_tasks_invalidate_pspace_data (objfile->pspace);
-    }
+  /* The associated program-space data might have changed after
+     this objfile was added.  Invalidate all cached data.  */
+  ada_tasks_invalidate_pspace_data (pspace);
 
   /* Invalidate the per-inferior cache for all inferiors using
-     this objfile (or, in other words, for all inferiors who have
-     the same program-space as the objfile's program space).
-     If all objfiles are being cleared (OBJFILE is NULL), then
-     clear the caches for all inferiors.  */
-
+     this program space.  */
   for (inferior *inf : all_inferiors ())
-    if (objfile == NULL || inf->pspace == objfile->pspace)
+    if (inf->pspace == pspace)
       ada_tasks_invalidate_inferior_data (inf);
 }
 
+/* Called when a new objfile was added.  */
+
+static void
+ada_tasks_new_objfile_observer (objfile *objfile)
+{
+  ada_tasks_clear_pspace_data (objfile->pspace);
+}
+
 /* The qcs command line flags for the "task apply" commands.  Keep
    this in sync with the "frame apply" commands.  */
 
@@ -1667,6 +1660,8 @@ _initialize_tasks ()
 				      "ada-tasks");
   gdb::observers::new_objfile.attach (ada_tasks_new_objfile_observer,
 				      "ada-tasks");
+  gdb::observers::all_objfiles_removed.attach (ada_tasks_clear_pspace_data,
+					       "ada-tasks");
 
   static struct cmd_list_element *task_cmd_list;
   static struct cmd_list_element *task_apply_list;
diff --git a/gdb/agent.c b/gdb/agent.c
index e2ad3b5..d7e4858 100644
--- a/gdb/agent.c
+++ b/gdb/agent.c
@@ -65,7 +65,7 @@ set_can_use_agent (const char *args, int from_tty, struct cmd_list_element *c)
 static void
 agent_new_objfile (struct objfile *objfile)
 {
-  if (objfile == NULL || agent_loaded_p ())
+  if (agent_loaded_p ())
     return;
 
   if (can_use_agent == can_use_agent_off)
diff --git a/gdb/aix-thread.c b/gdb/aix-thread.c
index 1f7b3c5..2077491 100644
--- a/gdb/aix-thread.c
+++ b/gdb/aix-thread.c
@@ -1109,14 +1109,13 @@ pd_disable (inferior *inf)
 
 /* new_objfile observer callback.
 
-   If OBJFILE is non-null, check whether a threaded application is
-   being debugged, and if so, prepare for thread debugging.  */
+   Check whether a threaded application is being debugged, and if so, prepare
+   for thread debugging.  */
 
 static void
 new_objfile (struct objfile *objfile)
 {
-  if (objfile)
-    pd_enable (current_inferior ());
+  pd_enable (current_inferior ());
 }
 
 /* Attach to process specified by ARGS.  */
diff --git a/gdb/arm-tdep.c b/gdb/arm-tdep.c
index 2495284..7e069d1 100644
--- a/gdb/arm-tdep.c
+++ b/gdb/arm-tdep.c
@@ -2543,7 +2543,7 @@ arm_exidx_new_objfile (struct objfile *objfile)
   LONGEST i;
 
   /* If we've already touched this file, do nothing.  */
-  if (!objfile || arm_exidx_data_key.get (objfile->obfd.get ()) != NULL)
+  if (arm_exidx_data_key.get (objfile->obfd.get ()) != nullptr)
     return;
 
   /* Read contents of exception table and index.  */
diff --git a/gdb/auto-load.c b/gdb/auto-load.c
index 37a44cc..8bbe669 100644
--- a/gdb/auto-load.c
+++ b/gdb/auto-load.c
@@ -1138,7 +1138,11 @@ auto_load_section_scripts (struct objfile *objfile, const char *section_name)
     }
 }
 
-/* Load any auto-loaded scripts for OBJFILE.  */
+/* Load any auto-loaded scripts for OBJFILE.
+
+   Two flavors of auto-loaded scripts are supported.
+   1) based on the path to the objfile
+   2) from .debug_gdb_scripts section  */
 
 void
 load_auto_scripts_for_objfile (struct objfile *objfile)
@@ -1160,25 +1164,6 @@ load_auto_scripts_for_objfile (struct objfile *objfile)
   auto_load_section_scripts (objfile, AUTO_SECTION_NAME);
 }
 
-/* This is a new_objfile observer callback to auto-load scripts.
-
-   Two flavors of auto-loaded scripts are supported.
-   1) based on the path to the objfile
-   2) from .debug_gdb_scripts section  */
-
-static void
-auto_load_new_objfile (struct objfile *objfile)
-{
-  if (!objfile)
-    {
-      /* OBJFILE is NULL when loading a new "main" symbol-file.  */
-      clear_section_scripts (current_program_space);
-      return;
-    }
-
-  load_auto_scripts_for_objfile (objfile);
-}
-
 /* Collect scripts to be printed in a vec.  */
 
 struct collect_matching_scripts_data
@@ -1531,9 +1516,11 @@ _initialize_auto_load ()
     python_name_help, guile_name_help;
   const char *suffix;
 
-  gdb::observers::new_objfile.attach (auto_load_new_objfile,
+  gdb::observers::new_objfile.attach (load_auto_scripts_for_objfile,
 				      auto_load_new_objfile_observer_token,
 				      "auto-load");
+  gdb::observers::all_objfiles_removed.attach (clear_section_scripts,
+					       "auto-load");
   add_setshow_boolean_cmd ("gdb-scripts", class_support,
 			   &auto_load_gdb_scripts, _("\
 Enable or disable auto-loading of canned sequences of commands scripts."), _("\
diff --git a/gdb/auxv.c b/gdb/auxv.c
index cfb44ff..7e3efc5 100644
--- a/gdb/auxv.c
+++ b/gdb/auxv.c
@@ -344,23 +344,14 @@ invalidate_auxv_cache_inf (struct inferior *inf)
   auxv_inferior_data.clear (inf);
 }
 
-/* Invalidate current inferior's auxv cache when all symbol table data is
-   cleared (indicated by OBJFILE being nullptr).  */
+/* Invalidate the auxv cache for all inferiors using PSPACE.  */
 
 static void
-auxv_new_objfile_observer (struct objfile *objfile)
+auxv_all_objfiles_removed (program_space *pspace)
 {
-  if (objfile == nullptr)
-    {
-      /* When OBJFILE is nullptr, this indicates that all symbol files have
-	 been unloaded from the current program space.  Discard cached auxv
-	 information from any inferior within the effected program space.  */
-      for (inferior *inf : all_inferiors ())
-	{
-	  if (inf->pspace == current_program_space)
-	    invalidate_auxv_cache_inf (inf);
-	}
-    }
+  for (inferior *inf : all_inferiors ())
+    if (inf->pspace == current_program_space)
+      invalidate_auxv_cache_inf (inf);
 }
 
 /* See auxv.h.  */
@@ -624,5 +615,6 @@ This is information provided by the operating system at program startup."));
   /* Observers used to invalidate the auxv cache when needed.  */
   gdb::observers::inferior_exit.attach (invalidate_auxv_cache_inf, "auxv");
   gdb::observers::inferior_appeared.attach (invalidate_auxv_cache_inf, "auxv");
-  gdb::observers::new_objfile.attach (auxv_new_objfile_observer, "auxv");
+  gdb::observers::all_objfiles_removed.attach (auxv_all_objfiles_removed,
+					       "auxv");
 }
diff --git a/gdb/linux-thread-db.c b/gdb/linux-thread-db.c
index 16c250c..cef78f5 100644
--- a/gdb/linux-thread-db.c
+++ b/gdb/linux-thread-db.c
@@ -1278,13 +1278,12 @@ thread_db_new_objfile (struct objfile *objfile)
   /* This observer must always be called with inferior_ptid set
      correctly.  */
 
-  if (objfile != NULL
-      /* libpthread with separate debug info has its debug info file already
+  if (/* libpthread with separate debug info has its debug info file already
 	 loaded (and notified without successful thread_db initialization)
 	 the time gdb::observers::new_objfile.notify is called for the library itself.
 	 Static executables have their separate debug info loaded already
 	 before the inferior has started.  */
-      && objfile->separate_debug_objfile_backlink == NULL
+      objfile->separate_debug_objfile_backlink == NULL
       /* Only check for thread_db if we loaded libpthread,
 	 or if this is the main symbol file.
 	 We need to check OBJF_MAINLINE to handle the case of debugging
diff --git a/gdb/observable.c b/gdb/observable.c
index 93a842e..09613b2 100644
--- a/gdb/observable.c
+++ b/gdb/observable.c
@@ -42,6 +42,7 @@ DEFINE_OBSERVABLE (inferior_forked);
 DEFINE_OBSERVABLE (solib_loaded);
 DEFINE_OBSERVABLE (solib_unloaded);
 DEFINE_OBSERVABLE (new_objfile);
+DEFINE_OBSERVABLE (all_objfiles_removed);
 DEFINE_OBSERVABLE (free_objfile);
 DEFINE_OBSERVABLE (new_thread);
 DEFINE_OBSERVABLE (thread_exit);
diff --git a/gdb/observable.h b/gdb/observable.h
index d9fc5cb..5a21440 100644
--- a/gdb/observable.h
+++ b/gdb/observable.h
@@ -107,11 +107,12 @@ extern observable<struct so_list */* solib */> solib_loaded;
 extern observable<struct program_space */* pspace */, struct so_list */* solib */>
   solib_unloaded;
 
-/* The symbol file specified by OBJFILE has been loaded.  Called
-   with OBJFILE equal to NULL to indicate previously loaded symbol
-   table data has now been invalidated.  */
+/* The symbol file specified by OBJFILE has been loaded.  */
 extern observable<struct objfile */* objfile */> new_objfile;
 
+/*  All objfiles from PSPACE were removed.  */
+extern observable<program_space */* pspace */> all_objfiles_removed;
+
 /* The object file specified by OBJFILE is about to be freed.  */
 extern observable<struct objfile */* objfile */> free_objfile;
 
diff --git a/gdb/python/py-inferior.c b/gdb/python/py-inferior.c
index e7a9d82..1f20b9a 100644
--- a/gdb/python/py-inferior.c
+++ b/gdb/python/py-inferior.c
@@ -190,20 +190,22 @@ python_new_objfile (struct objfile *objfile)
   if (!gdb_python_initialized)
     return;
 
-  gdbpy_enter enter_py (objfile != NULL
-			? objfile->arch ()
-			: target_gdbarch ());
+  gdbpy_enter enter_py (objfile->arch ());
 
-  if (objfile == NULL)
-    {
-      if (emit_clear_objfiles_event (current_program_space) < 0)
-	gdbpy_print_stack ();
-    }
-  else
-    {
-      if (emit_new_objfile_event (objfile) < 0)
-	gdbpy_print_stack ();
-    }
+  if (emit_new_objfile_event (objfile) < 0)
+    gdbpy_print_stack ();
+}
+
+static void
+python_all_objfiles_removed (program_space *pspace)
+{
+  if (!gdb_python_initialized)
+    return;
+
+  gdbpy_enter enter_py (target_gdbarch ());
+
+  if (emit_clear_objfiles_event (pspace) < 0)
+    gdbpy_print_stack ();
 }
 
 /* Emit a Python event when an objfile is about to be removed.  */
@@ -1020,6 +1022,8 @@ gdbpy_initialize_inferior (void)
   gdb::observers::new_objfile.attach
     (python_new_objfile, "py-inferior",
      { &auto_load_new_objfile_observer_token });
+  gdb::observers::all_objfiles_removed.attach (python_all_objfiles_removed,
+					       "py-inferior");
   gdb::observers::free_objfile.attach (python_free_objfile, "py-inferior");
   gdb::observers::inferior_added.attach (python_new_inferior, "py-inferior");
   gdb::observers::inferior_removed.attach (python_inferior_deleted,
diff --git a/gdb/remote.c b/gdb/remote.c
index 9bb4f1d..ae08c98 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -14963,14 +14963,12 @@ show_remote_cmd (const char *args, int from_tty)
       }
 }
 
+/* Some change happened in PSPACE's objfile list (obfiles added or removed),
+   offer all inferiors using that program space a change to look up symbols.  */
 
-/* Function to be called whenever a new objfile (shlib) is detected.  */
 static void
-remote_new_objfile (struct objfile *objfile)
+remote_objfile_changed_check_symbols (program_space *pspace)
 {
-  /* The objfile change happened in that program space.  */
-  program_space *pspace = current_program_space;
-
   /* The affected program space is possibly shared by multiple inferiors.
      Consider sending a qSymbol packet for each of the inferiors using that
      program space.  */
@@ -15019,6 +15017,14 @@ remote_new_objfile (struct objfile *objfile)
   }
 }
 
+/* Function to be called whenever a new objfile (shlib) is detected.  */
+
+static void
+remote_new_objfile (struct objfile *objfile)
+{
+  remote_objfile_changed_check_symbols (objfile->pspace);
+}
+
 /* Pull all the tracepoints defined on the target and create local
    data structures representing them.  We don't want to create real
    tracepoints yet, we don't want to mess up the user's existing
@@ -15333,6 +15339,8 @@ _initialize_remote ()
 
   /* Hook into new objfile notification.  */
   gdb::observers::new_objfile.attach (remote_new_objfile, "remote");
+  gdb::observers::all_objfiles_removed.attach
+    (remote_objfile_changed_check_symbols, "remote");
 
 #if 0
   init_remote_threadtests ();
diff --git a/gdb/sol-thread.c b/gdb/sol-thread.c
index ed1a803..c152b44 100644
--- a/gdb/sol-thread.c
+++ b/gdb/sol-thread.c
@@ -668,8 +668,7 @@ check_for_thread_db (void)
 static void
 sol_thread_new_objfile (struct objfile *objfile)
 {
-  if (objfile != NULL)
-    check_for_thread_db ();
+  check_for_thread_db ();
 }
 
 /* Clean up after the inferior dies.  */
diff --git a/gdb/symfile.c b/gdb/symfile.c
index 584a62c..0f720d4 100644
--- a/gdb/symfile.c
+++ b/gdb/symfile.c
@@ -2915,7 +2915,7 @@ clear_symtab_users (symfile_add_flags add_flags)
   clear_displays ();
   clear_last_displayed_sal ();
   clear_pc_function_cache ();
-  gdb::observers::new_objfile.notify (NULL);
+  gdb::observers::all_objfiles_removed.notify (current_program_space);
 
   /* Now that the various caches have been cleared, we can re_set
      our breakpoints without risking it using stale data.  */
diff --git a/gdb/symtab.c b/gdb/symtab.c
index afad782..e9bc7b2 100644
--- a/gdb/symtab.c
+++ b/gdb/symtab.c
@@ -1695,13 +1695,18 @@ maintenance_print_symbol_cache_statistics (const char *args, int from_tty)
 static void
 symtab_new_objfile_observer (struct objfile *objfile)
 {
-  /* Ideally we'd use OBJFILE->pspace, but OBJFILE may be NULL.  */
-  symbol_cache_flush (current_program_space);
+  symbol_cache_flush (objfile->pspace);
+}
+
+/* This module's 'all_objfiles_removed' observer.  */
+
+static void
+symtab_all_objfiles_removed (program_space *pspace)
+{
+  symbol_cache_flush (pspace);
 
-  /* When all objfiles have been removed (OBJFILE is nullptr), then forget
-     everything we know about the main function.  */
-  if (objfile == nullptr)
-    set_main_name (current_program_space, nullptr, language_unknown);
+  /* Forget everything we know about the main function.  */
+  set_main_name (pspace, nullptr, language_unknown);
 }
 
 /* This module's 'free_objfile' observer.  */
@@ -7022,5 +7027,7 @@ the use of prologue scanners."),
   deprecate_cmd (c, "maintenancelist flush symbol-cache");
 
   gdb::observers::new_objfile.attach (symtab_new_objfile_observer, "symtab");
+  gdb::observers::all_objfiles_removed.attach (symtab_all_objfiles_removed,
+					       "symtab");
   gdb::observers::free_objfile.attach (symtab_free_objfile_observer, "symtab");
 }
diff --git a/gdb/tui/tui-hooks.c b/gdb/tui/tui-hooks.c
index d67c3d7..6525f0f 100644
--- a/gdb/tui/tui-hooks.c
+++ b/gdb/tui/tui-hooks.c
@@ -49,13 +49,20 @@
 
 #include "gdb_curses.h"
 
-static void
-tui_new_objfile_hook (struct objfile* objfile)
+static void tui_on_objfiles_changed ()
 {
   if (tui_active)
     tui_display_main ();
 }
 
+static void
+tui_new_objfile_hook (struct objfile* objfile)
+{ tui_on_objfiles_changed (); }
+
+static void
+tui_all_objfiles_removed (program_space *pspace)
+{ tui_on_objfiles_changed (); }
+
 /* Prevent recursion of deprecated_register_changed_hook().  */
 static bool tui_refreshing_registers = false;
 
@@ -283,4 +290,6 @@ _initialize_tui_hooks ()
 {
   /* Install the permanent hooks.  */
   gdb::observers::new_objfile.attach (tui_new_objfile_hook, "tui-hooks");
+  gdb::observers::all_objfiles_removed.attach (tui_all_objfiles_removed,
+					       "tui-hooks");
 }