[svn:parrot] r48635 - trunk/src/string

[nwellnhof at svn.parrot.org]

Author: nwellnhof
Date: Tue Aug 24 17:19:45 2010
New Revision: 48635
URL: https://trac.parrot.org/parrot/changeset/48635

Log:
Clarify handling of flags in str_copy

Modified:
   trunk/src/string/api.c

Modified: trunk/src/string/api.c
==============================================================================
--- trunk/src/string/api.c	Tue Aug 24 17:14:54 2010	(r48634)
+++ trunk/src/string/api.c	Tue Aug 24 17:19:45 2010	(r48635)
@@ -382,18 +382,21 @@
 Parrot_str_copy(PARROT_INTERP, ARGIN(const STRING *s))
 {
     ASSERT_ARGS(Parrot_str_copy)
-    STRING *d;
+    STRING * const d = Parrot_gc_new_string_header(interp, 0);
     const int is_movable = PObj_is_movable_TESTALL(s);
 
-    /* We set COW flag to avoid cloning buffer in compact_pool */
-
-    d = Parrot_gc_new_string_header(interp,
-        PObj_get_FLAGS(s) & ~PObj_constant_FLAG);
-    /* This overwrites the constant flag again. Not sure if this is OK */
+    /* Copy encoding/charset/etc */
     STRUCT_COPY(d, s);
 
-    /* Clear live flag. It might be set on constant strings */
-    PObj_live_CLEAR(d);
+    /* Only copy is_COWable, constant, and external flags.
+     * Note that it's important (and safe) to copy the constant flag
+     * although the copied string header is not allocated from the constant
+     * string header pool. */
+    PObj_get_FLAGS(d) =  PObj_is_string_FLAG
+                      | (PObj_get_FLAGS(s)
+                      & (PObj_is_COWable_FLAG
+                      |  PObj_constant_FLAG
+                      |  PObj_external_FLAG));
 
     /* Now check that buffer allocated from pool and affected by compacting */
     if (is_movable && Buffer_bufstart(s)) {