More documentation of obscure flags is good, even if the

documentation might be not so good. Atleast it's not false!
Documents the flags one can give to perl_clone

p4raw-id: //depot/perl@18306

diff --git a/sv.c b/sv.c
index a21cedf..d478583 100644 (file)
--- a/sv.c
+++ b/sv.c
@@ -10046,6 +10046,35 @@ Perl_ss_dup(pTHX_ PerlInterpreter *proto_perl, CLONE_PARAMS* param)
 
 Create and return a new interpreter by cloning the current one.
 
+perl_clone takes these flags as paramters:
+
+CLONEf_COPY_STACKS - is used to, well, copy the stacks also, 
+without it we only clone the data and zero the stacks, 
+with it we copy the stacks and the new perl interpreter is 
+ready to run at the exact same point as the previous one. 
+The pseudo-fork code uses COPY_STACKS while the 
+threads->new doesn't.
+
+CLONEf_KEEP_PTR_TABLE
+perl_clone keeps a ptr_table with the pointer of the old 
+variable as a key and the new variable as a value, 
+this allows it to check if something has been cloned and not 
+clone it again but rather just use the value and increase the 
+refcount. If KEEP_PTR_TABLE is not set then perl_clone will kill 
+the ptr_table using the function 
+C<ptr_table_free(PL_ptr_table); PL_ptr_table = NULL;>, 
+reason to keep it around is if you want to dup some of your own 
+variable who are outside the graph perl scans, example of this 
+code is in threads.xs create
+
+CLONEf_CLONE_HOST
+This is a win32 thing, it is ignored on unix, it tells perls 
+win32host code (which is c++) to clone itself, this is needed on 
+win32 if you want to run two threads at the same time, 
+if you just want to do some stuff in a separate perl interpreter 
+and then throw it away and return to the original one, 
+you don't need to do anything.
+
 =cut
 */