X-Git-Url: http://git.efficios.com/?a=blobdiff_plain;f=gdb%2Flinux-fork.c;h=c77fb6c73ac98dbef349e4af30d357bd451f2670;hb=5b6d1e4fa4fc6827c7b3f0e99ff120dfa14d65d2;hp=dbaa36eb4a7ad6467ebf24f7a64594425301cf1a;hpb=5826e159863b6cd69953dc01faf7c20414409909;p=deliverable%2Fbinutils-gdb.git

diff --git a/gdb/linux-fork.c b/gdb/linux-fork.c
index dbaa36eb4a..c77fb6c73a 100644
--- a/gdb/linux-fork.c
+++ b/gdb/linux-fork.c
@@ -1,6 +1,6 @@
 /* GNU/Linux native-dependent code for debugging multiple forks.
 
-   Copyright (C) 2005-2015 Free Software Foundation, Inc.
+   Copyright (C) 2005-2020 Free Software Foundation, Inc.
 
    This file is part of GDB.
 
@@ -31,133 +31,134 @@
 #include "source.h"
 
 #include "nat/gdb_ptrace.h"
-#include "gdb_wait.h"
+#include "gdbsupport/gdb_wait.h"
 #include <dirent.h>
 #include <ctype.h>
 
-struct fork_info *fork_list;
-static int highest_fork_num;
-
-/* Prevent warning from -Wmissing-prototypes.  */
-extern void _initialize_linux_fork (void);
+#include <list>
 
 /* Fork list data structure:  */
 struct fork_info
 {
-  struct fork_info *next;
-  ptid_t ptid;
-  ptid_t parent_ptid;
-  int num;			/* Convenient handle (GDB fork id).  */
-  struct regcache *savedregs;	/* Convenient for info fork, saves
-				   having to actually switch contexts.  */
-  int clobber_regs;		/* True if we should restore saved regs.  */
-  off_t *filepos;		/* Set of open file descriptors' offsets.  */
-  int maxfd;
+  explicit fork_info (pid_t pid)
+    : ptid (pid, pid, 0)
+  {
+  }
+
+  ~fork_info ()
+  {
+    /* Notes on step-resume breakpoints: since this is a concern for
+       threads, let's convince ourselves that it's not a concern for
+       forks.  There are two ways for a fork_info to be created.
+       First, by the checkpoint command, in which case we're at a gdb
+       prompt and there can't be any step-resume breakpoint.  Second,
+       by a fork in the user program, in which case we *may* have
+       stepped into the fork call, but regardless of whether we follow
+       the parent or the child, we will return to the same place and
+       the step-resume breakpoint, if any, will take care of itself as
+       usual.  And unlike threads, we do not save a private copy of
+       the step-resume breakpoint -- so we're OK.  */
+
+    if (savedregs)
+      delete savedregs;
+    if (filepos)
+      xfree (filepos);
+  }
+
+  ptid_t ptid = null_ptid;
+  ptid_t parent_ptid = null_ptid;
+
+  /* Convenient handle (GDB fork id).  */
+  int num = 0;
+
+  /* Convenient for info fork, saves having to actually switch
+     contexts.  */
+  readonly_detached_regcache *savedregs = nullptr;
+
+  CORE_ADDR pc = 0;
+
+  /* Set of open file descriptors' offsets.  */
+  off_t *filepos = nullptr;
+
+  int maxfd = 0;
 };
 
+static std::list<fork_info> fork_list;
+static int highest_fork_num;
+
 /* Fork list methods:  */
 
 int
 forks_exist_p (void)
 {
-  return (fork_list != NULL);
+  return !fork_list.empty ();
 }
 
-/* Add a fork to the internal fork list.  */
+/* Return the last fork in the list.  */
 
-struct fork_info *
-add_fork (pid_t pid)
+static struct fork_info *
+find_last_fork (void)
 {
-  struct fork_info *fp;
-
-  if (fork_list == NULL && pid != ptid_get_pid (inferior_ptid))
-    {
-      /* Special case -- if this is the first fork in the list
-	 (the list is hitherto empty), and if this new fork is
-	 NOT the current inferior_ptid, then add inferior_ptid
-	 first, as a special zeroeth fork id.  */
-      highest_fork_num = -1;
-      add_fork (ptid_get_pid (inferior_ptid));	/* safe recursion */
-    }
+  if (fork_list.empty ())
+    return NULL;
 
-  fp = XCNEW (struct fork_info);
-  fp->ptid = ptid_build (pid, pid, 0);
-  fp->num = ++highest_fork_num;
-  fp->next = fork_list;
-  fork_list = fp;
-  return fp;
+  return &fork_list.back ();
 }
 
-static void
-free_fork (struct fork_info *fp)
-{
-  /* Notes on step-resume breakpoints: since this is a concern for
-     threads, let's convince ourselves that it's not a concern for
-     forks.  There are two ways for a fork_info to be created.  First,
-     by the checkpoint command, in which case we're at a gdb prompt
-     and there can't be any step-resume breakpoint.  Second, by a fork
-     in the user program, in which case we *may* have stepped into the
-     fork call, but regardless of whether we follow the parent or the
-     child, we will return to the same place and the step-resume
-     breakpoint, if any, will take care of itself as usual.  And
-     unlike threads, we do not save a private copy of the step-resume
-     breakpoint -- so we're OK.  */
-
-  if (fp)
-    {
-      if (fp->savedregs)
-	regcache_xfree (fp->savedregs);
-      if (fp->filepos)
-	xfree (fp->filepos);
-      xfree (fp);
-    }
-}
+/* Return true iff there's one fork in the list.  */
 
-static void
-delete_fork (ptid_t ptid)
+static bool
+one_fork_p ()
 {
-  struct fork_info *fp, *fpprev;
-
-  fpprev = NULL;
-
-  linux_nat_forget_process (ptid_get_pid (ptid));
+  return (!fork_list.empty ()
+	  && &fork_list.front () == &fork_list.back ());
+}
 
-  for (fp = fork_list; fp; fpprev = fp, fp = fp->next)
-    if (ptid_equal (fp->ptid, ptid))
-      break;
+/* Add a new fork to the internal fork list.  */
 
-  if (!fp)
-    return;
+void
+add_fork (pid_t pid)
+{
+  fork_list.emplace_back (pid);
 
-  if (fpprev)
-    fpprev->next = fp->next;
-  else
-    fork_list = fp->next;
+  if (one_fork_p ())
+    highest_fork_num = 0;
 
-  free_fork (fp);
+  fork_info *fp = &fork_list.back ();
+  fp->num = ++highest_fork_num;
+}
 
-  /* Special case: if there is now only one process in the list,
-     and if it is (hopefully!) the current inferior_ptid, then
-     remove it, leaving the list empty -- we're now down to the
-     default case of debugging a single process.  */
-  if (fork_list != NULL && fork_list->next == NULL &&
-      ptid_equal (fork_list->ptid, inferior_ptid))
-    {
-      /* Last fork -- delete from list and handle as solo process
-	 (should be a safe recursion).  */
-      delete_fork (inferior_ptid);
-    }
+static void
+delete_fork (ptid_t ptid)
+{
+  linux_target->low_forget_process (ptid.pid ());
+
+  for (auto it = fork_list.begin (); it != fork_list.end (); ++it)
+    if (it->ptid == ptid)
+      {
+	fork_list.erase (it);
+
+	/* Special case: if there is now only one process in the list,
+	   and if it is (hopefully!) the current inferior_ptid, then
+	   remove it, leaving the list empty -- we're now down to the
+	   default case of debugging a single process.  */
+	if (one_fork_p () && fork_list.front ().ptid == inferior_ptid)
+	  {
+	    /* Last fork -- delete from list and handle as solo
+	       process (should be a safe recursion).  */
+	    delete_fork (inferior_ptid);
+	  }
+	return;
+      }
 }
 
 /* Find a fork_info by matching PTID.  */
 static struct fork_info *
 find_fork_ptid (ptid_t ptid)
 {
-  struct fork_info *fp;
-
-  for (fp = fork_list; fp; fp = fp->next)
-    if (ptid_equal (fp->ptid, ptid))
-      return fp;
+  for (fork_info &fi : fork_list)
+    if (fi.ptid == ptid)
+      return &fi;
 
   return NULL;
 }
@@ -166,11 +167,9 @@ find_fork_ptid (ptid_t ptid)
 static struct fork_info *
 find_fork_id (int num)
 {
-  struct fork_info *fp;
-
-  for (fp = fork_list; fp; fp = fp->next)
-    if (fp->num == num)
-      return fp;
+  for (fork_info &fi : fork_list)
+    if (fi.num == num)
+      return &fi;
 
   return NULL;
 }
@@ -179,11 +178,9 @@ find_fork_id (int num)
 extern struct fork_info *
 find_fork_pid (pid_t pid)
 {
-  struct fork_info *fp;
-
-  for (fp = fork_list; fp; fp = fp->next)
-    if (pid == ptid_get_pid (fp->ptid))
-      return fp;
+  for (fork_info &fi : fork_list)
+    if (pid == fi.ptid.pid ())
+      return &fi;
 
   return NULL;
 }
@@ -195,24 +192,7 @@ fork_id_to_ptid (int num)
   if (fork)
     return fork->ptid;
   else
-    return pid_to_ptid (-1);
-}
-
-static void
-init_fork_list (void)
-{
-  struct fork_info *fp, *fpnext;
-
-  if (!fork_list)
-    return;
-
-  for (fp = fork_list; fp; fp = fpnext)
-    {
-      fpnext = fp->next;
-      free_fork (fp);
-    }
-
-  fork_list = NULL;
+    return ptid_t (-1);
 }
 
 /* Fork list <-> gdb interface.  */
@@ -225,7 +205,7 @@ call_lseek (int fd, off_t offset, int whence)
 {
   char exp[80];
 
-  snprintf (&exp[0], sizeof (exp), "lseek (%d, %ld, %d)",
+  snprintf (&exp[0], sizeof (exp), "(long) lseek (%d, %ld, %d)",
 	    fd, (long) offset, whence);
   return (off_t) parse_and_eval_long (&exp[0]);
 }
@@ -235,18 +215,18 @@ call_lseek (int fd, off_t offset, int whence)
 static void
 fork_load_infrun_state (struct fork_info *fp)
 {
-  extern void nullify_last_target_wait_ptid ();
   int i;
 
   linux_nat_switch_fork (fp->ptid);
 
-  if (fp->savedregs && fp->clobber_regs)
-    regcache_cpy (get_current_regcache (), fp->savedregs);
+  if (fp->savedregs)
+    get_current_regcache ()->restore (fp->savedregs);
 
   registers_changed ();
   reinit_frame_cache ();
 
-  stop_pc = regcache_read_pc (get_current_regcache ());
+  inferior_thread ()->suspend.stop_pc
+    = regcache_read_pc (get_current_regcache ());
   nullify_last_target_wait_ptid ();
 
   /* Now restore the file positions of open file descriptors.  */
@@ -261,59 +241,53 @@ fork_load_infrun_state (struct fork_info *fp)
     }
 }
 
-/* Save infrun state for the fork PTID.
-   Exported for use by linux child_follow_fork.  */
+/* Save infrun state for the fork FP.  */
 
 static void
-fork_save_infrun_state (struct fork_info *fp, int clobber_regs)
+fork_save_infrun_state (struct fork_info *fp)
 {
   char path[PATH_MAX];
   struct dirent *de;
   DIR *d;
 
   if (fp->savedregs)
-    regcache_xfree (fp->savedregs);
+    delete fp->savedregs;
 
-  fp->savedregs = regcache_dup (get_current_regcache ());
-  fp->clobber_regs = clobber_regs;
+  fp->savedregs = new readonly_detached_regcache (*get_current_regcache ());
+  fp->pc = regcache_read_pc (get_current_regcache ());
 
-  if (clobber_regs)
+  /* Now save the 'state' (file position) of all open file descriptors.
+     Unfortunately fork does not take care of that for us...  */
+  snprintf (path, PATH_MAX, "/proc/%ld/fd", (long) fp->ptid.pid ());
+  if ((d = opendir (path)) != NULL)
     {
-      /* Now save the 'state' (file position) of all open file descriptors.
-	 Unfortunately fork does not take care of that for us...  */
-      snprintf (path, PATH_MAX, "/proc/%ld/fd",
-		(long) ptid_get_pid (fp->ptid));
-      if ((d = opendir (path)) != NULL)
+      long tmp;
+
+      fp->maxfd = 0;
+      while ((de = readdir (d)) != NULL)
 	{
-	  long tmp;
-
-	  fp->maxfd = 0;
-	  while ((de = readdir (d)) != NULL)
-	    {
-	      /* Count open file descriptors (actually find highest
-		 numbered).  */
-	      tmp = strtol (&de->d_name[0], NULL, 10);
-	      if (fp->maxfd < tmp)
-		fp->maxfd = tmp;
-	    }
-	  /* Allocate array of file positions.  */
-	  fp->filepos = xrealloc (fp->filepos,
-				  (fp->maxfd + 1) * sizeof (*fp->filepos));
-
-	  /* Initialize to -1 (invalid).  */
-	  for (tmp = 0; tmp <= fp->maxfd; tmp++)
-	    fp->filepos[tmp] = -1;
-
-	  /* Now find actual file positions.  */
-	  rewinddir (d);
-	  while ((de = readdir (d)) != NULL)
-	    if (isdigit (de->d_name[0]))
-	      {
-		tmp = strtol (&de->d_name[0], NULL, 10);
-		fp->filepos[tmp] = call_lseek (tmp, 0, SEEK_CUR);
-	      }
-	  closedir (d);
+	  /* Count open file descriptors (actually find highest
+	     numbered).  */
+	  tmp = strtol (&de->d_name[0], NULL, 10);
+	  if (fp->maxfd < tmp)
+	    fp->maxfd = tmp;
 	}
+      /* Allocate array of file positions.  */
+      fp->filepos = XRESIZEVEC (off_t, fp->filepos, fp->maxfd + 1);
+
+      /* Initialize to -1 (invalid).  */
+      for (tmp = 0; tmp <= fp->maxfd; tmp++)
+	fp->filepos[tmp] = -1;
+
+      /* Now find actual file positions.  */
+      rewinddir (d);
+      while ((de = readdir (d)) != NULL)
+	if (isdigit (de->d_name[0]))
+	  {
+	    tmp = strtol (&de->d_name[0], NULL, 10);
+	    fp->filepos[tmp] = call_lseek (tmp, 0, SEEK_CUR);
+	  }
+      closedir (d);
     }
 }
 
@@ -327,13 +301,12 @@ linux_fork_killall (void)
      status for it) -- however any process may be a child
      or a parent, so may get a SIGCHLD from a previously
      killed child.  Wait them all out.  */
-  struct fork_info *fp;
-  pid_t pid, ret;
-  int status;
 
-  for (fp = fork_list; fp; fp = fp->next)
+  for (fork_info &fi : fork_list)
     {
-      pid = ptid_get_pid (fp->ptid);
+      pid_t pid = fi.ptid.pid ();
+      int status;
+      pid_t ret;
       do {
 	/* Use SIGKILL instead of PTRACE_KILL because the former works even
 	   if the thread is running, while the later doesn't.  */
@@ -344,7 +317,9 @@ linux_fork_killall (void)
 	 died.  MVS comment cut-and-pasted from linux-nat.  */
       } while (ret == pid && WIFSTOPPED (status));
     }
-  init_fork_list ();	/* Clear list, prepare to start fresh.  */
+
+  /* Clear list, prepare to start fresh.  */
+  fork_list.clear ();
 }
 
 /* The current inferior_ptid has exited, but there are other viable
@@ -354,13 +329,14 @@ linux_fork_killall (void)
 void
 linux_fork_mourn_inferior (void)
 {
+  struct fork_info *last;
+  int status;
+
   /* Wait just one more time to collect the inferior's exit status.
      Do not check whether this succeeds though, since we may be
      dealing with a process that we attached to.  Such a process will
      only report its exit status to its original parent.  */
-  int status;
-
-  waitpid (ptid_get_pid (inferior_ptid), &status, 0);
+  waitpid (inferior_ptid.pid (), &status, 0);
 
   /* OK, presumably inferior_ptid is the one who has exited.
      We need to delete that one from the fork_list, and switch
@@ -370,14 +346,15 @@ linux_fork_mourn_inferior (void)
   /* There should still be a fork - if there's only one left,
      delete_fork won't remove it, because we haven't updated
      inferior_ptid yet.  */
-  gdb_assert (fork_list);
+  gdb_assert (!fork_list.empty ());
 
-  fork_load_infrun_state (fork_list);
+  last = find_last_fork ();
+  fork_load_infrun_state (last);
   printf_filtered (_("[Switching to %s]\n"),
-		   target_pid_to_str (inferior_ptid));
+		   target_pid_to_str (inferior_ptid).c_str ());
 
   /* If there's only one fork, switch back to non-fork mode.  */
-  if (fork_list->next == NULL)
+  if (one_fork_p ())
     delete_fork (inferior_ptid);
 }
 
@@ -386,72 +363,101 @@ linux_fork_mourn_inferior (void)
    the first available.  */
 
 void
-linux_fork_detach (const char *args, int from_tty)
+linux_fork_detach (int from_tty)
 {
   /* OK, inferior_ptid is the one we are detaching from.  We need to
      delete it from the fork_list, and switch to the next available
      fork.  */
 
-  if (ptrace (PTRACE_DETACH, ptid_get_pid (inferior_ptid), 0, 0))
-    error (_("Unable to detach %s"), target_pid_to_str (inferior_ptid));
+  if (ptrace (PTRACE_DETACH, inferior_ptid.pid (), 0, 0))
+    error (_("Unable to detach %s"),
+	   target_pid_to_str (inferior_ptid).c_str ());
 
   delete_fork (inferior_ptid);
 
   /* There should still be a fork - if there's only one left,
      delete_fork won't remove it, because we haven't updated
      inferior_ptid yet.  */
-  gdb_assert (fork_list);
+  gdb_assert (!fork_list.empty ());
 
-  fork_load_infrun_state (fork_list);
+  fork_load_infrun_state (&fork_list.front ());
 
   if (from_tty)
     printf_filtered (_("[Switching to %s]\n"),
-		     target_pid_to_str (inferior_ptid));
+		     target_pid_to_str (inferior_ptid).c_str ());
 
   /* If there's only one fork, switch back to non-fork mode.  */
-  if (fork_list->next == NULL)
+  if (one_fork_p ())
     delete_fork (inferior_ptid);
 }
 
-static void
-inferior_call_waitpid_cleanup (void *fp)
-{
-  struct fork_info *oldfp = fp;
+/* Temporarily switch to the infrun state stored on the fork_info
+   identified by a given ptid_t.  When this object goes out of scope,
+   restore the currently selected infrun state.   */
 
-  if (oldfp)
-    {
-      /* Switch back to inferior_ptid.  */
-      remove_breakpoints ();
-      fork_load_infrun_state (oldfp);
-      insert_breakpoints ();
-    }
-}
+class scoped_switch_fork_info
+{
+public:
+  /* Switch to the infrun state held on the fork_info identified by
+     PPTID.  If PPTID is the current inferior then no switch is done.  */
+  explicit scoped_switch_fork_info (ptid_t pptid)
+    : m_oldfp (nullptr)
+  {
+    if (pptid != inferior_ptid)
+      {
+	struct fork_info *newfp = nullptr;
+
+	/* Switch to pptid.  */
+	m_oldfp = find_fork_ptid (inferior_ptid);
+	gdb_assert (m_oldfp != nullptr);
+	newfp = find_fork_ptid (pptid);
+	gdb_assert (newfp != nullptr);
+	fork_save_infrun_state (m_oldfp);
+	remove_breakpoints ();
+	fork_load_infrun_state (newfp);
+	insert_breakpoints ();
+      }
+  }
+
+  /* Restore the previously selected infrun state.  If the constructor
+     didn't need to switch states, then nothing is done here either.  */
+  ~scoped_switch_fork_info ()
+  {
+    if (m_oldfp != nullptr)
+      {
+	/* Switch back to inferior_ptid.  */
+	try
+	  {
+	    remove_breakpoints ();
+	    fork_load_infrun_state (m_oldfp);
+	    insert_breakpoints ();
+	  }
+	catch (const gdb_exception &ex)
+	  {
+	    warning (_("Couldn't restore checkpoint state in %s: %s"),
+		     target_pid_to_str (m_oldfp->ptid).c_str (),
+		     ex.what ());
+	  }
+      }
+  }
+
+  DISABLE_COPY_AND_ASSIGN (scoped_switch_fork_info);
+
+private:
+  /* The fork_info for the previously selected infrun state, or nullptr if
+     we were already in the desired state, and nothing needs to be
+     restored.  */
+  struct fork_info *m_oldfp;
+};
 
 static int
 inferior_call_waitpid (ptid_t pptid, int pid)
 {
   struct objfile *waitpid_objf;
   struct value *waitpid_fn = NULL;
-  struct value *argv[4], *retv;
-  struct gdbarch *gdbarch = get_current_arch ();
-  struct fork_info *oldfp = NULL, *newfp = NULL;
-  struct cleanup *old_cleanup;
   int ret = -1;
 
-  if (!ptid_equal (pptid, inferior_ptid))
-    {
-      /* Switch to pptid.  */
-      oldfp = find_fork_ptid (inferior_ptid);
-      gdb_assert (oldfp != NULL);
-      newfp = find_fork_ptid (pptid);
-      gdb_assert (newfp != NULL);
-      fork_save_infrun_state (oldfp, 1);
-      remove_breakpoints ();
-      fork_load_infrun_state (newfp);
-      insert_breakpoints ();
-    }
-
-  old_cleanup = make_cleanup (inferior_call_waitpid_cleanup, oldfp);
+  scoped_switch_fork_info switch_fork_info (pptid);
 
   /* Get the waitpid_fn.  */
   if (lookup_minimal_symbol ("waitpid", NULL, NULL).minsym != NULL)
@@ -459,30 +465,29 @@ inferior_call_waitpid (ptid_t pptid, int pid)
   if (!waitpid_fn
       && lookup_minimal_symbol ("_waitpid", NULL, NULL).minsym != NULL)
     waitpid_fn = find_function_in_inferior ("_waitpid", &waitpid_objf);
-  if (!waitpid_fn)
-    goto out;
+  if (waitpid_fn != nullptr)
+    {
+      struct gdbarch *gdbarch = get_current_arch ();
+      struct value *argv[3], *retv;
 
-  /* Get the argv.  */
-  argv[0] = value_from_longest (builtin_type (gdbarch)->builtin_int, pid);
-  argv[1] = value_from_pointer (builtin_type (gdbarch)->builtin_data_ptr, 0);
-  argv[2] = value_from_longest (builtin_type (gdbarch)->builtin_int, 0);
-  argv[3] = 0;
+      /* Get the argv.  */
+      argv[0] = value_from_longest (builtin_type (gdbarch)->builtin_int, pid);
+      argv[1] = value_from_pointer (builtin_type (gdbarch)->builtin_data_ptr, 0);
+      argv[2] = value_from_longest (builtin_type (gdbarch)->builtin_int, 0);
 
-  retv = call_function_by_hand (waitpid_fn, 3, argv);
-  if (value_as_long (retv) < 0)
-    goto out;
+      retv = call_function_by_hand (waitpid_fn, NULL, argv);
 
-  ret = 0;
+      if (value_as_long (retv) >= 0)
+	ret = 0;
+    }
 
-out:
-  do_cleanups (old_cleanup);
   return ret;
 }
 
 /* Fork list <-> user interface.  */
 
 static void
-delete_checkpoint_command (char *args, int from_tty)
+delete_checkpoint_command (const char *args, int from_tty)
 {
   ptid_t ptid, pptid;
   struct fork_info *fi;
@@ -491,39 +496,41 @@ delete_checkpoint_command (char *args, int from_tty)
     error (_("Requires argument (checkpoint id to delete)"));
 
   ptid = fork_id_to_ptid (parse_and_eval_long (args));
-  if (ptid_equal (ptid, minus_one_ptid))
+  if (ptid == minus_one_ptid)
     error (_("No such checkpoint id, %s"), args);
 
-  if (ptid_equal (ptid, inferior_ptid))
+  if (ptid == inferior_ptid)
     error (_("\
 Please switch to another checkpoint before deleting the current one"));
 
-  if (ptrace (PTRACE_KILL, ptid_get_pid (ptid), 0, 0))
-    error (_("Unable to kill pid %s"), target_pid_to_str (ptid));
+  if (ptrace (PTRACE_KILL, ptid.pid (), 0, 0))
+    error (_("Unable to kill pid %s"), target_pid_to_str (ptid).c_str ());
 
   fi = find_fork_ptid (ptid);
   gdb_assert (fi);
   pptid = fi->parent_ptid;
 
   if (from_tty)
-    printf_filtered (_("Killed %s\n"), target_pid_to_str (ptid));
+    printf_filtered (_("Killed %s\n"), target_pid_to_str (ptid).c_str ());
 
   delete_fork (ptid);
 
   /* If fi->parent_ptid is not a part of lwp but it's a part of checkpoint
      list, waitpid the ptid.
-     If fi->parent_ptid is a part of lwp and it is stoped, waitpid the
+     If fi->parent_ptid is a part of lwp and it is stopped, waitpid the
      ptid.  */
-  if ((!find_thread_ptid (pptid) && find_fork_ptid (pptid))
-      || (find_thread_ptid (pptid) && is_stopped (pptid)))
+  thread_info *parent = find_thread_ptid (linux_target, pptid);
+  if ((parent == NULL && find_fork_ptid (pptid))
+      || (parent != NULL && parent->state == THREAD_STOPPED))
     {
-      if (inferior_call_waitpid (pptid, ptid_get_pid (ptid)))
-        warning (_("Unable to wait pid %s"), target_pid_to_str (ptid));
+      if (inferior_call_waitpid (pptid, ptid.pid ()))
+        warning (_("Unable to wait pid %s"),
+		 target_pid_to_str (ptid).c_str ());
     }
 }
 
 static void
-detach_checkpoint_command (char *args, int from_tty)
+detach_checkpoint_command (const char *args, int from_tty)
 {
   ptid_t ptid;
 
@@ -531,18 +538,18 @@ detach_checkpoint_command (char *args, int from_tty)
     error (_("Requires argument (checkpoint id to detach)"));
 
   ptid = fork_id_to_ptid (parse_and_eval_long (args));
-  if (ptid_equal (ptid, minus_one_ptid))
+  if (ptid == minus_one_ptid)
     error (_("No such checkpoint id, %s"), args);
 
-  if (ptid_equal (ptid, inferior_ptid))
+  if (ptid == inferior_ptid)
     error (_("\
 Please switch to another checkpoint before detaching the current one"));
 
-  if (ptrace (PTRACE_DETACH, ptid_get_pid (ptid), 0, 0))
-    error (_("Unable to detach %s"), target_pid_to_str (ptid));
+  if (ptrace (PTRACE_DETACH, ptid.pid (), 0, 0))
+    error (_("Unable to detach %s"), target_pid_to_str (ptid).c_str ());
 
   if (from_tty)
-    printf_filtered (_("Detached %s\n"), target_pid_to_str (ptid));
+    printf_filtered (_("Detached %s\n"), target_pid_to_str (ptid).c_str ());
 
   delete_fork (ptid);
 }
@@ -550,41 +557,34 @@ Please switch to another checkpoint before detaching the current one"));
 /* Print information about currently known checkpoints.  */
 
 static void
-info_checkpoints_command (char *arg, int from_tty)
+info_checkpoints_command (const char *arg, int from_tty)
 {
   struct gdbarch *gdbarch = get_current_arch ();
-  struct symtab_and_line sal;
-  struct fork_info *fp;
-  ULONGEST pc;
   int requested = -1;
-  struct fork_info *printed = NULL;
+  const fork_info *printed = NULL;
 
   if (arg && *arg)
     requested = (int) parse_and_eval_long (arg);
 
-  for (fp = fork_list; fp; fp = fp->next)
+  for (const fork_info &fi : fork_list)
     {
-      if (requested > 0 && fp->num != requested)
+      if (requested > 0 && fi.num != requested)
 	continue;
 
-      printed = fp;
-      if (ptid_equal (fp->ptid, inferior_ptid))
-	{
-	  printf_filtered ("* ");
-	  pc = regcache_read_pc (get_current_regcache ());
-	}
+      printed = &fi;
+      if (fi.ptid == inferior_ptid)
+	printf_filtered ("* ");
       else
-	{
-	  printf_filtered ("  ");
-	  pc = regcache_read_pc (fp->savedregs);
-	}
-      printf_filtered ("%d %s", fp->num, target_pid_to_str (fp->ptid));
-      if (fp->num == 0)
+	printf_filtered ("  ");
+
+      ULONGEST pc = fi.pc;
+      printf_filtered ("%d %s", fi.num, target_pid_to_str (fi.ptid).c_str ());
+      if (fi.num == 0)
 	printf_filtered (_(" (main process)"));
       printf_filtered (_(" at "));
       fputs_filtered (paddress (gdbarch, pc), gdb_stdout);
 
-      sal = find_pc_line (pc, 0);
+      symtab_and_line sal = find_pc_line (pc, 0);
       if (sal.symtab)
 	printf_filtered (_(", file %s"),
 			 symtab_to_filename_for_display (sal.symtab));
@@ -596,7 +596,7 @@ info_checkpoints_command (char *arg, int from_tty)
 
 	  msym = lookup_minimal_symbol_by_pc (pc);
 	  if (msym.minsym)
-	    printf_filtered (", <%s>", MSYMBOL_LINKAGE_NAME (msym.minsym));
+	    printf_filtered (", <%s>", msym.minsym->linkage_name ());
 	}
 
       putchar_filtered ('\n');
@@ -619,35 +619,24 @@ linux_fork_checkpointing_p (int pid)
   return (checkpointing_pid == pid);
 }
 
-/* Callback for iterate over threads.  Used to check whether
-   the current inferior is multi-threaded.  Returns true as soon
-   as it sees the second thread of the current inferior.  */
-
-static int
-inf_has_multiple_thread_cb (struct thread_info *tp, void *data)
-{
-  int *count_p = (int *) data;
-  
-  if (current_inferior ()->pid == ptid_get_pid (tp->ptid))
-    (*count_p)++;
-  
-  /* Stop the iteration if multiple threads have been detected.  */
-  return *count_p > 1;
-}
-
 /* Return true if the current inferior is multi-threaded.  */
 
-static int
-inf_has_multiple_threads (void)
+static bool
+inf_has_multiple_threads ()
 {
   int count = 0;
 
-  iterate_over_threads (inf_has_multiple_thread_cb, &count);
-  return (count > 1);
+  /* Return true as soon as we see the second thread of the current
+     inferior.  */
+  for (thread_info *tp ATTRIBUTE_UNUSED : current_inferior ()->threads ())
+    if (++count > 1)
+      return true;
+
+  return false;
 }
 
 static void
-checkpoint_command (char *args, int from_tty)
+checkpoint_command (const char *args, int from_tty)
 {
   struct objfile *fork_objf;
   struct gdbarch *gdbarch;
@@ -656,7 +645,6 @@ checkpoint_command (char *args, int from_tty)
   struct value *fork_fn = NULL, *ret;
   struct fork_info *fp;
   pid_t retpid;
-  struct cleanup *old_chain;
 
   if (!target_has_execution) 
     error (_("The program is not being run."));
@@ -680,16 +668,18 @@ checkpoint_command (char *args, int from_tty)
   ret = value_from_longest (builtin_type (gdbarch)->builtin_int, 0);
 
   /* Tell linux-nat.c that we're checkpointing this inferior.  */
-  old_chain = make_cleanup_restore_integer (&checkpointing_pid);
-  checkpointing_pid = ptid_get_pid (inferior_ptid);
+  {
+    scoped_restore save_pid
+      = make_scoped_restore (&checkpointing_pid, inferior_ptid.pid ());
+
+    ret = call_function_by_hand (fork_fn, NULL, {});
+  }
 
-  ret = call_function_by_hand (fork_fn, 0, &ret);
-  do_cleanups (old_chain);
   if (!ret)	/* Probably can't happen.  */
     error (_("checkpoint: call_function_by_hand returned null."));
 
   retpid = value_as_long (ret);
-  get_last_target_status (&last_target_ptid, &last_target_waitstatus);
+  get_last_target_status (nullptr, &last_target_ptid, &last_target_waitstatus);
 
   fp = find_fork_pid (retpid);
 
@@ -701,9 +691,9 @@ checkpoint_command (char *args, int from_tty)
 		       fp != NULL ? fp->num : -1, (long) retpid);
       if (info_verbose)
 	{
-	  parent_pid = ptid_get_lwp (last_target_ptid);
+	  parent_pid = last_target_ptid.lwp ();
 	  if (parent_pid == 0)
-	    parent_pid = ptid_get_pid (last_target_ptid);
+	    parent_pid = last_target_ptid.pid ();
 	  printf_filtered (_("   gdb says parent = %ld.\n"),
 			   (long) parent_pid);
 	}
@@ -711,7 +701,16 @@ checkpoint_command (char *args, int from_tty)
 
   if (!fp)
     error (_("Failed to find new fork"));
-  fork_save_infrun_state (fp, 1);
+
+  if (one_fork_p ())
+    {
+      /* Special case -- if this is the first fork in the list (the
+	 list was hitherto empty), then add inferior_ptid first, as a
+	 special zeroeth fork id.  */
+      fork_list.emplace_front (inferior_ptid.pid ());
+    }
+
+  fork_save_infrun_state (fp);
   fp->parent_ptid = last_target_ptid;
 }
 
@@ -726,20 +725,20 @@ linux_fork_context (struct fork_info *newfp, int from_tty)
   oldfp = find_fork_ptid (inferior_ptid);
   gdb_assert (oldfp != NULL);
 
-  fork_save_infrun_state (oldfp, 1);
+  fork_save_infrun_state (oldfp);
   remove_breakpoints ();
   fork_load_infrun_state (newfp);
   insert_breakpoints ();
 
   printf_filtered (_("Switching to %s\n"),
-		   target_pid_to_str (inferior_ptid));
+		   target_pid_to_str (inferior_ptid).c_str ());
 
   print_stack_frame (get_selected_frame (NULL), 1, SRC_AND_LOC, 1);
 }
 
 /* Switch inferior process (checkpoint) context, by checkpoint id.  */
 static void
-restart_command (char *args, int from_tty)
+restart_command (const char *args, int from_tty)
 {
   struct fork_info *fp;
 
@@ -755,8 +754,6 @@ restart_command (char *args, int from_tty)
 void
 _initialize_linux_fork (void)
 {
-  init_fork_list ();
-
   /* Checkpoint command: create a fork of the inferior process
      and set it aside for later debugging.  */
 
@@ -767,8 +764,9 @@ Fork a duplicate process (experimental)."));
      process.  */
 
   add_com ("restart", class_obscure, restart_command, _("\
-restart <n>: restore program context from a checkpoint.\n\
-Argument 'n' is checkpoint ID, as displayed by 'info checkpoints'."));
+Restore program context from a checkpoint.\n\
+Usage: restart N\n\
+Argument N is checkpoint ID, as displayed by 'info checkpoints'."));
 
   /* Delete checkpoint command: kill the process and remove it from
      the fork list.  */