Allow to start marker threads in child of single-threaded client

Now GC_start_mark_threads() is present even if the collector is
single-threaded (the function does nothing in this case).

* include/gc/gc.h (GC_start_mark_threads): Declare unconditionally
(i.e. even w/o GC_THREADS).
* misc.c (GC_start_mark_threads): Define unconditionally (no-op in
case of GC_THREADS is not defined).
* tests/gctest.c [!NO_TEST_HANDLE_FORK && !GC_THREADS] (run_one_test):
Call GC_start_mark_threads().

3 files changed, 12 insertions, 16 deletions

diff --git a/include/gc/gc.h b/include/gc/gc.h
index 29e967a1..6c643b13 100644
--- a/include/gc/gc.h
+++ b/include/gc/gc.h
@@ -512,7 +512,7 @@ GC_API void GC_CALL GC_set_handle_fork(int);
 /* before fork(); GC_atfork_parent should be invoked just after fork in */
 /* the branch that corresponds to parent process (i.e., fork result is  */
 /* non-zero); GC_atfork_child is to be called immediately in the child  */
-/* branch (i.e., fork result is 0). Note that GC_atfork_child() call    */
+/* branch (i.e., fork result is 0).  Note that GC_atfork_child() call   */
 /* should, of course, precede GC_start_mark_threads call (if any).      */
 GC_API void GC_CALL GC_atfork_prepare(void);
 GC_API void GC_CALL GC_atfork_parent(void);
@@ -1510,6 +1510,11 @@ GC_API void * GC_CALL GC_call_with_stack_base(GC_stack_base_func /* fn */,
 #define GC_NOT_FOUND 4          /* Requested link not found (returned   */
                                 /* by GC_move_disappearing_link).       */
 
+/* Restart marker threads after POSIX fork in child.  Meaningless in    */
+/* other situations.  Should not be called if fork followed by exec.    */
+/* Acquires the GC lock to avoid a data race.                           */
+GC_API void GC_CALL GC_start_mark_threads(void);
+
 #if defined(GC_DARWIN_THREADS) || defined(GC_WIN32_THREADS)
   /* Use implicit thread registration and processing (via Win32 DllMain */
   /* or Darwin task_threads).  Deprecated.  Must be called before       */
@@ -1538,11 +1543,6 @@ GC_API void * GC_CALL GC_call_with_stack_base(GC_stack_base_func /* fn */,
   /* systems.  Return -1 otherwise.                                     */
   GC_API int GC_CALL GC_get_thr_restart_signal(void);
 
-  /* Restart marker threads after POSIX fork in child.  Meaningless in  */
-  /* other situations.  Should not be called if fork followed by exec.  */
-  /* Acquires the GC lock to avoid a data race.                         */
-  GC_API void GC_CALL GC_start_mark_threads(void);
-
   /* Explicitly enable GC_register_my_thread() invocation.              */
   /* Done implicitly if a GC thread-creation function is called (or     */
   /* implicit thread registration is activated, or the collector is     */
diff --git a/misc.c b/misc.c
index 646dbb31..7f53729d 100644
--- a/misc.c
+++ b/misc.c
@@ -1445,9 +1445,8 @@ GC_API void GC_CALL GC_enable_incremental(void)
   GC_init();
 }
 
-#if defined(THREADS)
-  GC_API void GC_CALL GC_start_mark_threads(void)
-  {
+GC_API void GC_CALL GC_start_mark_threads(void)
+{
 #   if defined(PARALLEL_MARK) && defined(CAN_HANDLE_FORK) \
        && !defined(THREAD_SANITIZER)
       /* TSan does not support threads creation in the child process.   */
@@ -1463,8 +1462,7 @@ GC_API void GC_CALL GC_enable_incremental(void)
       /* No action since parallel markers are disabled (or no POSIX fork). */
       GC_ASSERT(I_DONT_HOLD_LOCK());
 #   endif
-  }
-#endif
+}
 
   GC_API void GC_CALL GC_deinit(void)
   {
diff --git a/tests/gctest.c b/tests/gctest.c
index 11235121..717873d2 100644
--- a/tests/gctest.c
+++ b/tests/gctest.c
@@ -1601,12 +1601,10 @@ void run_one_test(void)
           if (print_stats)
             GC_log_printf("Started a child process, pid= %ld\n",
                           (long)child_pid);
-#         ifdef THREADS
-#           ifdef PARALLEL_MARK
-              GC_gcollect(); /* no parallel markers */
-#           endif
-            GC_start_mark_threads();
+#         ifdef PARALLEL_MARK
+            GC_gcollect(); /* no parallel markers */
 #         endif
+          GC_start_mark_threads();
           GC_gcollect();
 #         ifdef THREADS
             /* Skip "Premature finalization" check in the       */