gdb: make inferior_list use intrusive_list

Change inferior_list, the global list of inferiors, to use
intrusive_list.  I think most other changes are somewhat obvious
fallouts from this change.

There is a small change in behavior in scoped_mock_context.  Before this
patch, constructing a scoped_mock_context would replace the whole
inferior list with only the new mock inferior.  Tests using two
scoped_mock_contexts therefore needed to manually link the two inferiors
together, as the second scoped_mock_context would bump the first mock
inferior from the thread list.  With this patch, a scoped_mock_context
adds its mock inferior to the inferior list on construction, and removes
it on destruction.  This means that tests run with mock inferiors in the
inferior list in addition to any pre-existing inferiors (there is always
at least one).  There is no possible pid clash problem, since each
scoped mock inferior uses its own process target, and pids are per
process target.

Co-Authored-By: Simon Marchi <simon.marchi@efficios.com>
Change-Id: I7eb6a8f867d4dcf8b8cd2dcffd118f7270756018

10 files changed, 103 insertions, 116 deletions

diff --git a/gdb/ada-tasks.c b/gdb/ada-tasks.c
index a9c6b5e..80a7221 100644
--- a/gdb/ada-tasks.c
+++ b/gdb/ada-tasks.c
@@ -1444,8 +1444,6 @@ ada_tasks_normal_stop_observer (struct bpstats *unused_args, int unused_args2)
 static void
 ada_tasks_new_objfile_observer (struct objfile *objfile)
 {
-  struct inferior *inf;
-
   /* Invalidate the relevant data in our program-space data.  */
 
   if (objfile == NULL)
@@ -1468,7 +1466,7 @@ ada_tasks_new_objfile_observer (struct objfile *objfile)
      If all objfiles are being cleared (OBJFILE is NULL), then
      clear the caches for all inferiors.  */
 
-  for (inf = inferior_list; inf != NULL; inf = inf->next)
+  for (inferior *inf : all_inferiors ())
     if (objfile == NULL || inf->pspace == objfile->pspace)
       ada_tasks_invalidate_inferior_data (inf);
 }
diff --git a/gdb/inferior-iter.h b/gdb/inferior-iter.h
index f999150..1701465 100644
--- a/gdb/inferior-iter.h
+++ b/gdb/inferior-iter.h
@@ -36,18 +36,21 @@ public:
   typedef int difference_type;
 
   /* Create an iterator pointing at HEAD.  */
-  all_inferiors_iterator (process_stratum_target *proc_target, inferior *head)
-    : m_proc_target (proc_target)
+  all_inferiors_iterator (process_stratum_target *proc_target,
+			  const intrusive_list<inferior> &list)
+    : m_proc_target (proc_target), m_inf_iter (list.begin ())
   {
+    intrusive_list<inferior>::iterator end;
+
     /* Advance M_INF to the first inferior's position.  */
-    for (m_inf = head; m_inf != NULL; m_inf = m_inf->next)
+    for (; m_inf_iter != end; ++m_inf_iter)
       if (m_inf_matches ())
 	return;
   }
 
   /* Create a one-past-end iterator.  */
   all_inferiors_iterator ()
-    : m_proc_target (nullptr), m_inf (nullptr)
+    : m_proc_target (nullptr)
   {}
 
   all_inferiors_iterator &operator++ ()
@@ -57,37 +60,39 @@ public:
   }
 
   inferior *operator* () const
-  { return m_inf; }
+  { return &*m_inf_iter; }
 
   bool operator!= (const all_inferiors_iterator &other) const
-  { return m_inf != other.m_inf; }
+  { return m_inf_iter != other.m_inf_iter; }
 
 private:
   /* Advance to next inferior, skipping filtered inferiors.  */
   void advance ()
   {
+    intrusive_list<inferior>::iterator end;
+
     /* The loop below is written in the natural way as-if we'd always
        start at the beginning of the inferior list.  This
        fast-forwards the algorithm to the actual current position.  */
     goto start;
 
-    while (m_inf != NULL)
+    while (m_inf_iter != end)
       {
 	if (m_inf_matches ())
 	  return;
       start:
-	m_inf = m_inf->next;
+	++m_inf_iter;
       }
   }
 
   bool m_inf_matches ()
   {
     return (m_proc_target == nullptr
-	    || m_proc_target == m_inf->process_target ());
+	    || m_proc_target == m_inf_iter->process_target ());
   }
 
   process_stratum_target *m_proc_target;
-  inferior *m_inf;
+  intrusive_list<inferior>::iterator m_inf_iter;
 };
 
 /* A range adapter that makes it possible to iterate over all
diff --git a/gdb/inferior.c b/gdb/inferior.c
index 3accf97..9681aaf 100644
--- a/gdb/inferior.c
+++ b/gdb/inferior.c
@@ -41,7 +41,7 @@
 
 DEFINE_REGISTRY (inferior, REGISTRY_ACCESS_FIELD)
 
-struct inferior *inferior_list = NULL;
+intrusive_list<inferior> inferior_list;
 static int highest_inferior_num;
 
 /* See inferior.h.  */
@@ -126,16 +126,7 @@ add_inferior_silent (int pid)
 {
   inferior *inf = new inferior (pid);
 
-  if (inferior_list == NULL)
-    inferior_list = inf;
-  else
-    {
-      inferior *last;
-
-      for (last = inferior_list; last->next != NULL; last = last->next)
-	;
-      last->next = inf;
-    }
+  inferior_list.push_back (*inf);
 
   gdb::observers::inferior_added.notify (inf);
 
@@ -177,25 +168,12 @@ inferior::clear_thread_list (bool silent)
 }
 
 void
-delete_inferior (struct inferior *todel)
+delete_inferior (struct inferior *inf)
 {
-  struct inferior *inf, *infprev;
-
-  infprev = NULL;
-
-  for (inf = inferior_list; inf; infprev = inf, inf = inf->next)
-    if (inf == todel)
-      break;
-
-  if (!inf)
-    return;
-
   inf->clear_thread_list (true);
 
-  if (infprev)
-    infprev->next = inf->next;
-  else
-    inferior_list = inf->next;
+  auto it = inferior_list.iterator_to (*inf);
+  inferior_list.erase (it);
 
   gdb::observers::inferior_removed.notify (inf);
 
@@ -210,17 +188,8 @@ delete_inferior (struct inferior *todel)
    exit of its threads.  */
 
 static void
-exit_inferior_1 (struct inferior *inftoex, int silent)
+exit_inferior_1 (struct inferior *inf, int silent)
 {
-  struct inferior *inf;
-
-  for (inf = inferior_list; inf; inf = inf->next)
-    if (inf == inftoex)
-      break;
-
-  if (!inf)
-    return;
-
   inf->clear_thread_list (silent);
 
   gdb::observers::inferior_exit.notify (inf);
@@ -388,22 +357,14 @@ have_live_inferiors (void)
 void
 prune_inferiors (void)
 {
-  inferior *ss;
-
-  ss = inferior_list;
-  while (ss)
+  for (inferior *inf : all_inferiors_safe ())
     {
-      if (!ss->deletable ()
-	  || !ss->removable
-	  || ss->pid != 0)
-	{
-	  ss = ss->next;
-	  continue;
-	}
+      if (!inf->deletable ()
+	  || !inf->removable
+	  || inf->pid != 0)
+	continue;
 
-      inferior *ss_next = ss->next;
-      delete_inferior (ss);
-      ss = ss_next;
+      delete_inferior (inf);
     }
 }
 
diff --git a/gdb/inferior.h b/gdb/inferior.h
index 2ae9f9a..830dec3 100644
--- a/gdb/inferior.h
+++ b/gdb/inferior.h
@@ -55,6 +55,7 @@ struct thread_info;
 #include "gdbsupport/refcounted-object.h"
 #include "gdbsupport/forward-scope-exit.h"
 #include "gdbsupport/gdb_unique_ptr.h"
+#include "gdbsupport/intrusive_list.h"
 
 #include "gdbsupport/common-inferior.h"
 #include "gdbthread.h"
@@ -339,7 +340,8 @@ extern void switch_to_inferior_no_thread (inferior *inf);
    listed exactly once in the inferior list, so placing an inferior in
    the inferior list is an implicit, not counted strong reference.  */
 
-class inferior : public refcounted_object
+class inferior : public refcounted_object,
+		 public intrusive_list_node<inferior>
 {
 public:
   explicit inferior (int pid);
@@ -387,9 +389,6 @@ public:
   bool has_execution ()
   { return target_has_execution (this); }
 
-  /* Pointer to next inferior in singly-linked list of inferiors.  */
-  struct inferior *next = NULL;
-
   /* This inferior's thread list, sorted by creation order.  */
   intrusive_list<thread_info> thread_list;
 
@@ -653,7 +652,7 @@ private:
 
 /* Traverse all inferiors.  */
 
-extern struct inferior *inferior_list;
+extern intrusive_list<inferior> inferior_list;
 
 /* Pull in the internals of the inferiors ranges and iterators.  Must
    be done after struct inferior is defined.  */
diff --git a/gdb/infrun.c b/gdb/infrun.c
index 8cfd58b..300d627 100644
--- a/gdb/infrun.c
+++ b/gdb/infrun.c
@@ -3730,18 +3730,28 @@ do_target_wait (execution_control_state *ecs, target_wait_flags options)
      reported the stop to the user, polling for events.  */
   scoped_restore_current_thread restore_thread;
 
-  int inf_num = selected->num;
-  for (inferior *inf = selected; inf != NULL; inf = inf->next)
-    if (inferior_matches (inf))
-      if (do_wait (inf))
+  intrusive_list_iterator<inferior> start
+    = inferior_list.iterator_to (*selected);
+
+  for (intrusive_list_iterator<inferior> it = start;
+       it != inferior_list.end ();
+       ++it)
+    {
+      inferior *inf = &*it;
+
+      if (inferior_matches (inf) && do_wait (inf))
 	return true;
+    }
 
-  for (inferior *inf = inferior_list;
-       inf != NULL && inf->num < inf_num;
-       inf = inf->next)
-    if (inferior_matches (inf))
-      if (do_wait (inf))
+  for (intrusive_list_iterator<inferior> it = inferior_list.begin ();
+       it != start;
+       ++it)
+    {
+      inferior *inf = &*it;
+
+      if (inferior_matches (inf) && do_wait (inf))
 	return true;
+    }
 
   ecs->ws.kind = TARGET_WAITKIND_IGNORE;
   return false;
@@ -9452,7 +9462,6 @@ infrun_thread_ptid_changed ()
 
     scoped_mock_context<test_target_ops> target1 (arch);
     scoped_mock_context<test_target_ops> target2 (arch);
-    target2.mock_inferior.next = &target1.mock_inferior;
 
     ptid_t old_ptid (111, 222);
     ptid_t new_ptid (111, 333);
@@ -9477,7 +9486,6 @@ infrun_thread_ptid_changed ()
 
     scoped_mock_context<test_target_ops> target1 (arch);
     scoped_mock_context<test_target_ops> target2 (arch);
-    target2.mock_inferior.next = &target1.mock_inferior;
 
     ptid_t old_ptid (111, 222);
     ptid_t new_ptid (111, 333);
diff --git a/gdb/progspace.c b/gdb/progspace.c
index e3cc692..7080bf8 100644
--- a/gdb/progspace.c
+++ b/gdb/progspace.c
@@ -404,7 +404,6 @@ void
 update_address_spaces (void)
 {
   int shared_aspace = gdbarch_has_shared_address_space (target_gdbarch ());
-  struct inferior *inf;
 
   init_address_spaces ();
 
@@ -423,7 +422,7 @@ update_address_spaces (void)
 	pspace->aspace = new_address_space ();
       }
 
-  for (inf = inferior_list; inf; inf = inf->next)
+  for (inferior *inf : all_inferiors ())
     if (gdbarch_has_global_solist (target_gdbarch ()))
       inf->aspace = maybe_new_address_space ();
     else
diff --git a/gdb/regcache.c b/gdb/regcache.c
index fde0c61..21fa25d 100644
--- a/gdb/regcache.c
+++ b/gdb/regcache.c
@@ -2038,7 +2038,6 @@ regcache_thread_ptid_changed ()
   /* Prepare two targets with one thread each, with the same ptid.  */
   scoped_mock_context<test_target_ops> target1 (arch);
   scoped_mock_context<test_target_ops> target2 (arch);
-  target2.mock_inferior.next = &target1.mock_inferior;
 
   ptid_t old_ptid (111, 222);
   ptid_t new_ptid (111, 333);
diff --git a/gdb/scoped-mock-context.h b/gdb/scoped-mock-context.h
index 37ffe51..ba3b81e 100644
--- a/gdb/scoped-mock-context.h
+++ b/gdb/scoped-mock-context.h
@@ -44,13 +44,12 @@ struct scoped_mock_context
 
   scoped_restore_current_pspace_and_thread restore_pspace_thread;
 
-  /* Add the mock inferior to the inferior list so that look ups by
-     target+ptid can find it.  */
-  scoped_restore_tmpl<inferior *> restore_inferior_list
-    {&inferior_list, &mock_inferior};
-
   explicit scoped_mock_context (gdbarch *gdbarch)
   {
+    /* Add the mock inferior to the inferior list so that look ups by
+       target+ptid can find it.  */
+    inferior_list.push_back (mock_inferior);
+
     mock_inferior.thread_list.push_back (mock_thread);
     mock_inferior.gdbarch = gdbarch;
     mock_inferior.aspace = mock_pspace.aspace;
@@ -70,6 +69,7 @@ struct scoped_mock_context
 
   ~scoped_mock_context ()
   {
+    inferior_list.erase (inferior_list.iterator_to (mock_inferior));
     pop_all_targets_at_and_above (process_stratum);
   }
 };
diff --git a/gdb/thread-iter.c b/gdb/thread-iter.c
index a1cdd02..31b7a36 100644
--- a/gdb/thread-iter.c
+++ b/gdb/thread-iter.c
@@ -26,15 +26,18 @@
 all_threads_iterator::all_threads_iterator (begin_t)
 {
   /* Advance M_INF/M_THR to the first thread's position.  */
-  for (m_inf = inferior_list; m_inf != NULL; m_inf = m_inf->next)
+
+  for (inferior &inf : inferior_list)
     {
-      auto thr_iter = m_inf->thread_list.begin ();
-      if (thr_iter != m_inf->thread_list.end ())
+      auto thr_iter = inf.thread_list.begin ();
+      if (thr_iter != inf.thread_list.end ())
 	{
+	  m_inf = &inf;
 	  m_thr = &*thr_iter;
 	  return;
 	}
     }
+  m_inf = nullptr;
   m_thr = nullptr;
 }
 
@@ -43,6 +46,7 @@ all_threads_iterator::all_threads_iterator (begin_t)
 void
 all_threads_iterator::advance ()
 {
+  intrusive_list<inferior>::iterator inf_iter (m_inf);
   intrusive_list<thread_info>::iterator thr_iter (m_thr);
 
   /* The loop below is written in the natural way as-if we'd always
@@ -50,8 +54,9 @@ all_threads_iterator::advance ()
      the algorithm to the actual current position.  */
   goto start;
 
-  for (; m_inf != NULL; m_inf = m_inf->next)
+  for (; inf_iter != inferior_list.end (); ++inf_iter)
     {
+      m_inf = &*inf_iter;
       thr_iter = m_inf->thread_list.begin ();
       while (thr_iter != m_inf->thread_list.end ())
 	{
@@ -86,16 +91,21 @@ all_matching_threads_iterator::all_matching_threads_iterator
   gdb_assert ((filter_target == nullptr && filter_ptid == minus_one_ptid)
 	      || filter_target->stratum () == process_stratum);
 
-  for (m_inf = inferior_list; m_inf != NULL; m_inf = m_inf->next)
-    if (m_inf_matches ())
-      for (auto thr_iter = m_inf->thread_list.begin ();
-	   thr_iter != m_inf->thread_list.end ();
-	   ++thr_iter)
-	if (thr_iter->ptid.matches (m_filter_ptid))
+  for (inferior &inf : inferior_list)
+    {
+      m_inf = &inf;
+      if (m_inf_matches ())
+	for (auto thr_iter = m_inf->thread_list.begin ();
+	     thr_iter != m_inf->thread_list.end ();
+	     ++thr_iter)
 	  {
-	    m_thr = &*thr_iter;
-	    return;
+	    if (thr_iter->ptid.matches (m_filter_ptid))
+	      {
+		m_thr = &*thr_iter;
+		return;
+	      }
 	  }
+    }
 
   m_thr = nullptr;
 }
@@ -105,6 +115,7 @@ all_matching_threads_iterator::all_matching_threads_iterator
 void
 all_matching_threads_iterator::advance ()
 {
+  intrusive_list<inferior>::iterator inf_iter (m_inf);
   intrusive_list<thread_info>::iterator thr_iter (m_thr);
 
   /* The loop below is written in the natural way as-if we'd always
@@ -112,21 +123,24 @@ all_matching_threads_iterator::advance ()
      the algorithm to the actual current position.  */
   goto start;
 
-  for (; m_inf != NULL; m_inf = m_inf->next)
-    if (m_inf_matches ())
-      {
-	thr_iter = m_inf->thread_list.begin ();
-	while (thr_iter != m_inf->thread_list.end ())
-	  {
-	    if (thr_iter->ptid.matches (m_filter_ptid))
-	      {
-		m_thr = &*thr_iter;
-		return;
-	      }
-	  start:
-	    ++thr_iter;
-	  }
-      }
+  for (; inf_iter != inferior_list.end (); ++inf_iter)
+    {
+      m_inf = &*inf_iter;
+      if (m_inf_matches ())
+	{
+	  thr_iter = m_inf->thread_list.begin ();
+	  while (thr_iter != m_inf->thread_list.end ())
+	    {
+	      if (thr_iter->ptid.matches (m_filter_ptid))
+		{
+		  m_thr = &*thr_iter;
+		  return;
+		}
+	    start:
+	      ++thr_iter;
+	    }
+	}
+    }
 
   m_thr = nullptr;
 }
diff --git a/gdb/thread.c b/gdb/thread.c
index 89f51c0..506e93c 100644
--- a/gdb/thread.c
+++ b/gdb/thread.c
@@ -1395,7 +1395,11 @@ show_thread_that_caused_stop (void)
 int
 show_inferior_qualified_tids (void)
 {
-  return (inferior_list->next != NULL || inferior_list->num != 1);
+  auto inf = inferior_list.begin ();
+  if (inf->num != 1)
+    return true;
+  ++inf;
+  return inf != inferior_list.end ();
 }
 
 /* See gdbthread.h.  */