add a comment why FreeBSD can't use MAP_STACK.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@32437 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 4 insertions, 0 deletions

diff --git a/cont.c b/cont.c
index 37c301a89d..b9634faff8 100644
--- a/cont.c
+++ b/cont.c
@@ -517,6 +517,10 @@ fiber_entry(void *arg)
 }
 #else /* _WIN32 */
 
+/*
+ * FreeBSD require a first (i.e. addr) argument of mmap(2) is not NULL
+ * if MAP_STACK is passed.
+ */
 #if defined(MAP_STACK) && !defined(__FreeBSD__)
 #define FIBER_STACK_FLAGS (MAP_PRIVATE | MAP_ANON | MAP_STACK)
 #else