Fix cast of struct-based pthread_t to void pointer on Win32

`THREAD_ID_TO_VPTR()` should be applied only to values of `thread_id_t`
type.  Another macro (`PTHREAD_TO_VPTR()`) should be defined and used
for 'pthread_t' values (this matters only Win32 platform when
`pthreads-win32` library is used).

* include/private/pthread_support.h (THREAD_ID_TO_VPTR): Move
definition upper to be near definition of `thread_id_self()`.
* include/private/pthread_support.h [GC_WIN32_THREADS]
(THREAD_ID_TO_VPTR): Define to `CAST_THRU_UINTPTR(void*,id)` regardless
of `CYGWIN32`, `GC_WIN32_PTHREADS`, `GC_PTHREADS_PARAMARK` and
`__WINPTHREADS_VERSION_MAJOR`.
* include/private/pthread_support.h [!GC_WIN32_THREADS]
(THREAD_ID_TO_VPTR): Redirect to `PTHREAD_TO_VPTR()`.
* include/private/pthread_support.h [GC_PTHREADS
|| GC_PTHREADS_PARAMARK] (PTHREAD_TO_VPTR): Define (similarly as
`THREAD_ID_TO_VPTR()` was defined previously); add comment.
* pthread_start.c [GC_PTHREADS && !PLATFORM_THREADS && !SN_TARGET_PSP2
&& DEBUG_THREADS && !GC_PTHREAD_START_STANDALONE]
(GC_pthread_start_inner): Use `PTHREAD_TO_VPTR()` instead of
`THREAD_ID_TO_VPTR()` (for a value of `pthread_t`).
* pthread_support.c [GC_PTHREADS && !PLATFORM_THREADS
&& !SN_TARGET_PSP2 && DEBUG_THREADS] (GC_wrap_pthread_join,
GC_start_rtn_prepare_thread, GC_wrap_pthread_create): Likewise.
* pthread_support.c [GC_PTHREADS_PARAMARK && GC_ASSERTIONS
&& GC_WIN32_THREADS && !USE_PTHREAD_LOCKS] (NUMERIC_THREAD_ID):
Likewise.
* win32_threads.c [STACKPTR_CORRECTOR_AVAILABLE && GC_PTHREADS]
(GC_push_stack_for): Likewise.
* win32_threads.c [STACKPTR_CORRECTOR_AVAILABLE] (GC_push_stack_for):
Check `GC_PTHREADS`.

include/private/pthread_support.h

@@ -139,10 +139,15 @@ typedef struct GC_StackContext_Rep {
 typedef DWORD thread_id_t;
 #    define thread_id_self() GetCurrentThreadId()
 #    define THREAD_ID_EQUAL(id1, id2) ((id1) == (id2))
+/* Convert a platform-specific thread id (of thread_id_t type) to   */
+/* some pointer identifying the thread.  This is used mostly for    */
+/* a debugging purpose when printing thread id.                     */
+#    define THREAD_ID_TO_VPTR(id) CAST_THRU_UINTPTR(void *, id)
 #  else
 typedef pthread_t thread_id_t;
 #    define thread_id_self() pthread_self()
 #    define THREAD_ID_EQUAL(id1, id2) THREAD_EQUAL(id1, id2)
+#    define THREAD_ID_TO_VPTR(id) PTHREAD_TO_VPTR(id)
 #  endif
 
 typedef struct GC_Thread_Rep {
@@ -275,17 +280,17 @@ typedef struct GC_Thread_Rep {
 #  endif
 } * GC_thread;
 
-/* Convert a platform-specific thread id (of thread_id_t type) to   */
-/* some pointer identifying the thread.  This is used mostly for    */
-/* a debugging purpose when printing thread id.                     */
-#  if defined(GC_WIN32_THREADS) && !defined(CYGWIN32)                  \
-      && (defined(GC_WIN32_PTHREADS) || defined(GC_PTHREADS_PARAMARK)) \
-      && !defined(__WINPTHREADS_VERSION_MAJOR)
+#  if defined(GC_PTHREADS) || defined(GC_PTHREADS_PARAMARK)
+/* Convert an opaque pthread_t value to a pointer identifying the thread. */
+#    if defined(GC_WIN32_THREADS) && !defined(CYGWIN32)                  \
+        && (defined(GC_WIN32_PTHREADS) || defined(GC_PTHREADS_PARAMARK)) \
+        && !defined(__WINPTHREADS_VERSION_MAJOR)
 /* Using documented internal details of pthreads-win32 library. */
 /* pthread_t is a struct.                                       */
-#    define THREAD_ID_TO_VPTR(id) ((void *)(id).p)
-#  else
-#    define THREAD_ID_TO_VPTR(id) CAST_THRU_UINTPTR(void *, id)
+#      define PTHREAD_TO_VPTR(id) ((void *)(id).p)
+#    else
+#      define PTHREAD_TO_VPTR(id) CAST_THRU_UINTPTR(void *, id)
+#    endif
 #  endif
 
 #  ifndef THREAD_TABLE_SZ

pthread_start.c

@@ -54,7 +54,7 @@ GC_pthread_start_inner(struct GC_stack_base *sb, void *arg)
 #  endif
   result = (*start)(start_arg);
 #  if defined(DEBUG_THREADS) && !defined(GC_PTHREAD_START_STANDALONE)
-  GC_log_printf("Finishing thread %p\n", THREAD_ID_TO_VPTR(pthread_self()));
+  GC_log_printf("Finishing thread %p\n", PTHREAD_TO_VPTR(pthread_self()));
 #  endif
   me->status = result;
   /* Note: we cannot use GC_dirty() instead.    */

pthread_support.c

@@ -2532,7 +2532,7 @@ GC_wrap_pthread_join(pthread_t thread, void **retval)
   INIT_REAL_SYMS();
 #    ifdef DEBUG_THREADS
   GC_log_printf("thread %p is joining thread %p\n",
-                THREAD_ID_TO_VPTR(pthread_self()), THREAD_ID_TO_VPTR(thread));
+                PTHREAD_TO_VPTR(pthread_self()), PTHREAD_TO_VPTR(thread));
 #    endif
 
   /* After the join, thread id may have been recycled.                */
@@ -2570,7 +2570,7 @@ GC_wrap_pthread_join(pthread_t thread, void **retval)
 
 #    ifdef DEBUG_THREADS
   GC_log_printf("thread %p join with thread %p %s\n",
-                THREAD_ID_TO_VPTR(pthread_self()), THREAD_ID_TO_VPTR(thread),
+                PTHREAD_TO_VPTR(pthread_self()), PTHREAD_TO_VPTR(thread),
                 result != 0 ? "failed" : "succeeded");
 #    endif
   return result;
@@ -2624,7 +2624,7 @@ GC_start_rtn_prepare_thread(void *(**pstart)(void *), void **pstart_arg,
 
 #    ifdef DEBUG_THREADS
   GC_log_printf("Starting thread %p, sp= %p\n",
-                THREAD_ID_TO_VPTR(pthread_self()), (void *)GC_approx_sp());
+                PTHREAD_TO_VPTR(pthread_self()), (void *)GC_approx_sp());
 #    endif
   /* If a GC occurs before the thread is registered, that GC will     */
   /* ignore this thread.  That's fine, since it will block trying to  */
@@ -2749,7 +2749,7 @@ GC_wrap_pthread_create(pthread_t *new_thread,
 #    endif
 #    ifdef DEBUG_THREADS
   GC_log_printf("About to start new thread from thread %p\n",
-                THREAD_ID_TO_VPTR(pthread_self()));
+                PTHREAD_TO_VPTR(pthread_self()));
 #    endif
   set_need_to_lock();
   result = REAL_FUNC(pthread_create)(new_thread, attr, GC_pthread_start, &si);
@@ -3004,8 +3004,7 @@ GC_lock(void)
 #    if defined(GC_ASSERTIONS) && defined(GC_WIN32_THREADS) \
         && !defined(USE_PTHREAD_LOCKS)
 /* Note: result is not guaranteed to be unique. */
-#      define NUMERIC_THREAD_ID(id) \
-        ((unsigned long)ADDR(THREAD_ID_TO_VPTR(id)))
+#      define NUMERIC_THREAD_ID(id) ((unsigned long)ADDR(PTHREAD_TO_VPTR(id)))
 #    endif
 
 #    ifdef GC_ASSERTIONS

win32_threads.c

@@ -908,9 +908,9 @@ GC_push_stack_for(GC_thread thread, thread_id_t self_id, GC_bool *pfound_me)
     }
 #  endif /* WOW64_THREAD_CONTEXT_WORKAROUND */
   }
-#  ifdef STACKPTR_CORRECTOR_AVAILABLE
+#  if defined(STACKPTR_CORRECTOR_AVAILABLE) && defined(GC_PTHREADS)
   if (GC_sp_corrector != 0)
-    GC_sp_corrector((void **)&sp, (void *)thread->pthread_id);
+    GC_sp_corrector((void **)&sp, PTHREAD_TO_VPTR(thread->pthread_id));
 #  endif
 
   /* Set stack_min to the lowest address in the thread stack,   */