Do not use syscall(2) on OS X 10.12 (deprecated).

src/pages.c

@@ -219,7 +219,7 @@ os_overcommits_proc(void)
 	char buf[1];
 	ssize_t nread;
 
-#ifdef SYS_open
+#if defined(JEMALLOC_HAVE_SYSCALL) && defined(SYS_open)
 	fd = (int)syscall(SYS_open, "/proc/sys/vm/overcommit_memory", O_RDONLY);
 #else
 	fd = open("/proc/sys/vm/overcommit_memory", O_RDONLY);
@@ -227,13 +227,13 @@ os_overcommits_proc(void)
 	if (fd == -1)
 		return (false); /* Error. */
 
-#ifdef SYS_read
+#if defined(JEMALLOC_HAVE_SYSCALL) && defined(SYS_read)
 	nread = (ssize_t)syscall(SYS_read, fd, &buf, sizeof(buf));
 #else
 	nread = read(fd, &buf, sizeof(buf));
 #endif
 
-#ifdef SYS_close
+#if defined(JEMALLOC_HAVE_SYSCALL) && defined(SYS_close)
 	syscall(SYS_close, fd);
 #else
 	close(fd);

src/util.c

@@ -49,7 +49,7 @@ static void
 wrtmessage(void *cbopaque, const char *s)
 {
 
-#ifdef SYS_write
+#if defined(JEMALLOC_HAVE_SYSCALL) && defined(SYS_write)
 	/*
 	 * Use syscall(2) rather than write(2) when possible in order to avoid
 	 * the possibility of memory allocation within libc.  This is necessary