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().

1 files changed, 3 insertions, 5 deletions

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)
   {