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>

1 files changed, 7 insertions, 15 deletions

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");
 }