Class-ify ptid_t

I grew a bit tired of using ptid_get_{lwp,pid,tid} and friends, so I decided to
make it a bit easier to use by making it a proper class.  The fields are now
private, so it's not possible to change a ptid_t field by mistake.

The new methods of ptid_t map to existing functions/practice like this:

  ptid_t (pid, lwp, tid) -> ptid_build (pid, lwp, tid)
  ptid_t (pid) -> pid_to_ptid (pid)
  ptid.is_pid () -> ptid_is_pid (ptid)
  ptid == other -> ptid_equal (ptid, other)
  ptid != other -> !ptid_equal (ptid, other)
  ptid.pid () -> ptid_get_pid (ptid)
  ptid.lwp_p () -> ptid_lwp_p (ptid)
  ptid.lwp () -> ptid_get_lwp (ptid)
  ptid.tid_p () -> ptid_tid_p (ptid)
  ptid.tid () -> ptid_get_tid (ptid)
  ptid.matches (filter) -> ptid_match (ptid, filter)

I've replaced the implementation of the existing functions with calls to
the new methods.  People are encouraged to gradually switch to using the
ptid_t methods instead of the functions (or we can change them all in
one pass eventually).

Also, I'm not sure if it's worth it (because of ptid_t's relatively
small size), but I have made the functions and methods take ptid_t
arguments by const reference instead of by value.

gdb/ChangeLog:

	* common/ptid.h (struct ptid): Change to...
	(class ptid_t): ... this.
	<ptid_t>: New constructors.
	<pid, lwp_p, lwp, tid_p, tid, is_pid, operator==, operator!=,
	matches>: New methods.
	<make_null, make_minus_one>: New static methods.
	<pid>: Rename to...
	<m_pid>: ...this.
	<lwp>: Rename to...
	<m_lwp>: ...this.
	<tid>: Rename to...
	<m_tid>: ...this.
	(ptid_build, ptid_get_pid, ptid_get_lwp, ptid_get_tid, ptid_equal,
	ptid_is_pid, ptid_lwp_p, ptid_tid_p, ptid_match): Take ptid arguments
	as references, move comment to class ptid_t.
	* common/ptid.c (null_ptid, minus_one_ptid): Initialize with
	ptid_t static methods.
	(ptid_build, pid_to_ptid, ptid_get_pid, ptid_get_tid,
	ptid_equal, ptid_is_pid, ptid_lwp_p, ptid_tid_p, ptid_match):
	Take ptid arguments as references, implement using ptid_t methods.
	* unittests/ptid-selftests.c: New file.
	* Makefile.in (SUBDIR_UNITTESTS_SRCS): Add
	unittests/ptid-selftests.c.
	(SUBDIR_UNITTESTS_OBS): Add unittests/ptid-selftests.o.

gdb/gdbserver/ChangeLog:

	* server.c (handle_v_cont): Initialize thread_resume::thread
	with null_ptid.

2 files changed, 160 insertions, 74 deletions

diff --git a/gdb/common/ptid.c b/gdb/common/ptid.c
index b56971b..81f16d0 100644
--- a/gdb/common/ptid.c
+++ b/gdb/common/ptid.c
@@ -22,20 +22,15 @@
 
 /* See ptid.h for these.  */
 
-ptid_t null_ptid = { 0, 0, 0 };
-ptid_t minus_one_ptid = { -1, 0, 0 };
+ptid_t null_ptid = ptid_t::make_null ();
+ptid_t minus_one_ptid = ptid_t::make_minus_one ();
 
 /* See ptid.h.  */
 
 ptid_t
 ptid_build (int pid, long lwp, long tid)
 {
-  ptid_t ptid;
-
-  ptid.pid = pid;
-  ptid.lwp = lwp;
-  ptid.tid = tid;
-  return ptid;
+  return ptid_t (pid, lwp, tid);
 }
 
 /* See ptid.h.  */
@@ -43,81 +38,69 @@ ptid_build (int pid, long lwp, long tid)
 ptid_t
 pid_to_ptid (int pid)
 {
-  return ptid_build (pid, 0, 0);
+  return ptid_t (pid);
 }
 
 /* See ptid.h.  */
 
 int
-ptid_get_pid (ptid_t ptid)
+ptid_get_pid (const ptid_t &ptid)
 {
-  return ptid.pid;
+  return ptid.pid ();
 }
 
 /* See ptid.h.  */
 
 long
-ptid_get_lwp (ptid_t ptid)
+ptid_get_lwp (const ptid_t &ptid)
 {
-  return ptid.lwp;
+  return ptid.lwp ();
 }
 
 /* See ptid.h.  */
 
 long
-ptid_get_tid (ptid_t ptid)
+ptid_get_tid (const ptid_t &ptid)
 {
-  return ptid.tid;
+  return ptid.tid ();
 }
 
 /* See ptid.h.  */
 
 int
-ptid_equal (ptid_t ptid1, ptid_t ptid2)
+ptid_equal (const ptid_t &ptid1, const ptid_t &ptid2)
 {
-  return (ptid1.pid == ptid2.pid
-	  && ptid1.lwp == ptid2.lwp
-	  && ptid1.tid == ptid2.tid);
+  return ptid1 == ptid2;
 }
 
 /* See ptid.h.  */
 
 int
-ptid_is_pid (ptid_t ptid)
+ptid_is_pid (const ptid_t &ptid)
 {
-  if (ptid_equal (minus_one_ptid, ptid)
-      || ptid_equal (null_ptid, ptid))
-    return 0;
-
-  return (ptid_get_lwp (ptid) == 0 && ptid_get_tid (ptid) == 0);
+  return ptid.is_pid ();
 }
 
 /* See ptid.h.  */
 
 int
-ptid_lwp_p (ptid_t ptid)
+ptid_lwp_p (const ptid_t &ptid)
 {
-  return (ptid_get_lwp (ptid) != 0);
+  return ptid.lwp_p ();
 }
 
 /* See ptid.h.  */
 
 int
-ptid_tid_p (ptid_t ptid)
+ptid_tid_p (const ptid_t &ptid)
 {
-  return (ptid_get_tid (ptid) != 0);
+  return ptid.tid_p ();
 }
 
+/* See ptid.h.  */
+
 int
-ptid_match (ptid_t ptid, ptid_t filter)
+ptid_match (const ptid_t &ptid, const ptid_t &filter)
 {
-  if (ptid_equal (filter, minus_one_ptid))
-    return 1;
-  if (ptid_is_pid (filter)
-      && ptid_get_pid (ptid) == ptid_get_pid (filter))
-    return 1;
-  else if (ptid_equal (ptid, filter))
-    return 1;
-
-  return 0;
+  return ptid.matches (filter);
 }
diff --git a/gdb/common/ptid.h b/gdb/common/ptid.h
index 337bfb0..70f5199 100644
--- a/gdb/common/ptid.h
+++ b/gdb/common/ptid.h
@@ -32,65 +32,168 @@
    thread_stratum target that might want to sit on top.
 */
 
-struct ptid
+class ptid_t
 {
+public:
+  /* Must have a trivial defaulted default constructor so that the
+     type remains POD.  */
+  ptid_t () noexcept = default;
+
+  /* Make a ptid given the necessary PID, LWP, and TID components.
+
+     A ptid with only a PID (LWP and TID equal to zero) is usually used to
+     represent a whole process, including all its lwps/threads.  */
+
+  explicit constexpr ptid_t (int pid, long lwp = 0, long tid = 0)
+    : m_pid (pid), m_lwp (lwp), m_tid (tid)
+  {}
+
+  /* Fetch the pid (process id) component from the ptid.  */
+
+  constexpr int pid () const
+  { return m_pid; }
+
+  /* Return true if the ptid's lwp member is non-zero.  */
+
+  constexpr bool lwp_p () const
+  { return m_lwp != 0; }
+
+  /* Fetch the lwp (lightweight process) component from the ptid.  */
+
+  constexpr long lwp () const
+  { return m_lwp; }
+
+  /* Return true if the ptid's tid member is non-zero.  */
+
+  constexpr bool tid_p () const
+  { return m_tid != 0; }
+
+  /* Fetch the tid (thread id) component from a ptid.  */
+
+  constexpr long tid () const
+  { return m_tid; }
+
+  /* Return true if the ptid represents a whole process, including all its
+     lwps/threads.  Such ptids have the form of (pid, 0, 0), with
+     pid != -1.  */
+
+  constexpr bool is_pid () const
+  {
+    return (*this != make_null ()
+	    && *this != make_minus_one ()
+	    && m_lwp == 0
+	    && m_tid == 0);
+  }
+
+  /* Compare two ptids to see if they are equal.  */
+
+  constexpr bool operator== (const ptid_t &other) const
+  {
+    return (m_pid == other.m_pid
+	    && m_lwp == other.m_lwp
+	    && m_tid == other.m_tid);
+  }
+
+  /* Compare two ptids to see if they are different.  */
+
+  constexpr bool operator!= (const ptid_t &other) const
+  {
+    return !(*this == other);
+  }
+
+  /* Return true if the ptid matches FILTER.  FILTER can be the wild
+     card MINUS_ONE_PTID (all ptids match it); can be a ptid representing
+     a process (ptid.is_pid () returns true), in which case, all lwps and
+     threads of that given process match, lwps and threads of other
+     processes do not; or, it can represent a specific thread, in which
+     case, only that thread will match true.  The ptid must represent a
+     specific LWP or THREAD, it can never be a wild card.  */
+
+  constexpr bool matches (const ptid_t &filter) const
+  {
+    return (/* If filter represents any ptid, it's always a match.  */
+	    filter == make_minus_one ()
+	    /* If filter is only a pid, any ptid with that pid
+	       matches.  */
+	    || (filter.is_pid () && m_pid == filter.pid ())
+
+	    /* Otherwise, this ptid only matches if it's exactly equal
+	       to filter.  */
+	    || *this == filter);
+  }
+
+  /* Make a null ptid.  */
+
+  static constexpr ptid_t make_null ()
+  { return ptid_t (0, 0, 0); }
+
+  /* Make a minus one ptid.  */
+
+  static constexpr ptid_t make_minus_one ()
+  { return ptid_t (-1, 0, 0); }
+
+private:
   /* Process id.  */
-  int pid;
+  int m_pid;
 
   /* Lightweight process id.  */
-  long lwp;
+  long m_lwp;
 
   /* Thread id.  */
-  long tid;
+  long m_tid;
 };
 
-typedef struct ptid ptid_t;
-
 /* The null or zero ptid, often used to indicate no process. */
+
 extern ptid_t null_ptid;
 
 /* The (-1,0,0) ptid, often used to indicate either an error condition
    or a "don't care" condition, i.e, "run all threads."  */
+
 extern ptid_t minus_one_ptid;
 
-/* Make a ptid given the necessary PID, LWP, and TID components.  */
-ptid_t ptid_build (int pid, long lwp, long tid);
 
-/* Make a new ptid from just a pid.  This ptid is usually used to
-   represent a whole process, including all its lwps/threads.  */
-ptid_t pid_to_ptid (int pid);
+/* The following functions are kept for backwards compatibility.  The use of
+   the ptid_t methods is preferred.  */
+
+/* See ptid_t::ptid_t.  */
+
+extern ptid_t ptid_build (int pid, long lwp, long tid);
+
+/* See ptid_t::ptid_t.  */
+
+extern ptid_t pid_to_ptid (int pid);
+
+/* See ptid_t::pid.  */
+
+extern int ptid_get_pid (const ptid_t &ptid);
+
+/* See ptid_t::lwp.  */
+
+extern long ptid_get_lwp (const ptid_t &ptid);
+
+/* See ptid_t::tid.  */
+
+extern long ptid_get_tid (const ptid_t &ptid);
+
+/* See ptid_t::operator== and ptid_t::operator!=.  */
 
-/* Fetch the pid (process id) component from a ptid.  */
-int ptid_get_pid (ptid_t ptid);
+extern int ptid_equal (const ptid_t &ptid1, const ptid_t &ptid2);
 
-/* Fetch the lwp (lightweight process) component from a ptid.  */
-long ptid_get_lwp (ptid_t ptid);
+/* See ptid_t::is_pid.  */
 
-/* Fetch the tid (thread id) component from a ptid.  */
-long ptid_get_tid (ptid_t ptid);
+extern int ptid_is_pid (const ptid_t &ptid);
 
-/* Compare two ptids to see if they are equal.  */
-int ptid_equal (ptid_t ptid1, ptid_t ptid2);
+/* See ptid_t::lwp_p.  */
 
-/* Returns true if PTID represents a whole process, including all its
-   lwps/threads.  Such ptids have the form of (pid,0,0), with pid !=
-   -1.  */
-int ptid_is_pid (ptid_t ptid);
+extern int ptid_lwp_p (const ptid_t &ptid);
 
-/* Return true if PTID's lwp member is non-zero.  */
-int ptid_lwp_p (ptid_t ptid);
+/* See ptid_t::tid_p.  */
 
-/* Return true if PTID's tid member is non-zero.  */
-int ptid_tid_p (ptid_t ptid);
+extern int ptid_tid_p (const ptid_t &ptid);
 
-/* Returns true if PTID matches filter FILTER.  FILTER can be the wild
-   card MINUS_ONE_PTID (all ptid match it); can be a ptid representing
-   a process (ptid_is_pid returns true), in which case, all lwps and
-   threads of that given process match, lwps and threads of other
-   processes do not; or, it can represent a specific thread, in which
-   case, only that thread will match true.  PTID must represent a
-   specific LWP or THREAD, it can never be a wild card.  */
+/* See ptid_t::matches.  */
 
-extern int ptid_match (ptid_t ptid, ptid_t filter);
+extern int ptid_match (const ptid_t &ptid, const ptid_t &filter);
 
 #endif