Add machinery to enable SHCOPY dynamically

This commit is just for debugging purposes, will probably be reverted.
It comes with a the erts_debug:copy_shared/1 BIF.  If SHCOPY_DISABLE
is defined, SHCOPY starts disabled and is dynamically enabled the first
time that the BIF is called.

1 files changed, 12 insertions, 0 deletions

diff --git a/erts/emulator/beam/copy.c b/erts/emulator/beam/copy.c
index b31e043f08..2566707717 100644
--- a/erts/emulator/beam/copy.c
+++ b/erts/emulator/beam/copy.c
@@ -901,6 +901,10 @@ Eterm copy_struct(Eterm obj, Uint sz, Eterm** hpp, ErlOffHeap* off_heap)
  *  Using an ESTACK but not very transparently; consider refactoring
  */
 
+#ifdef SHCOPY_DISABLE
+int disable_copy_shared = ERTS_SHCOPY_FLG_NONE;
+#endif
+
 #define DECLARE_SHTABLE(s)					\
     DECLARE_ESTACK(s);						\
     Uint ESTK_CONCAT(s,_offset) = 0
@@ -1028,6 +1032,10 @@ Uint copy_shared_calculate(Eterm obj, shcopy_info *info, unsigned flags)
     if (IS_CONST(obj))
 	return 0;
 
+#ifdef SHCOPY_DISABLE
+    flags |= disable_copy_shared;
+#endif
+
     myself = erts_get_current_process();
     if (myself == NULL || (flags & ERTS_SHCOPY_FLG_NONE))
 	return size_object(obj);
@@ -1276,6 +1284,10 @@ Uint copy_shared_perform(Eterm obj, Uint size, shcopy_info *info, Eterm** hpp, E
     if (IS_CONST(obj))
 	return obj;
 
+#ifdef SHCOPY_DISABLE
+    flags |= disable_copy_shared;
+#endif
+
     myself = erts_get_current_process();
     if (myself == NULL || (flags & ERTS_SHCOPY_FLG_NONE))
 	return copy_struct(obj, size, hpp, off_heap);