Add fix to sp_open. sp_once exposed a timing issue in sp_open where the

address of the context was not being set until the end of the routine.  This
does not work if the write attention AST is called before exiting sp_open,
which seems to be the case in simple testing of the sp_once routine.

sp_mgr.c

@@ -62,9 +62,11 @@
 **	12-JUL-2012 V1.5    Sneddon     Race condition in sp_send.  Thanks to
 **					  David G. North and Craig A. Berry.
 **	13-JUL-2012 V1.6    Sneddon	Add sp_once.
+**	24-JUL-2012 V1.6-1  Sneddon	Timing issue discovered by sp_once in
+**					  sp_open.  Comments for sp_once_ast.
 **--
 */
-#pragma module SP_MGR "V1.6"
+#pragma module SP_MGR "V1.6-1"
 
     struct SPB;
     typedef struct SPB *SPHANDLE;
@@ -196,6 +198,12 @@ unsigned int sp_open (SPHANDLE *ctxpp, void *inicmd, unsigned int (*rcvast)(void
 
     status = lib$get_vm(&spb_size, &ctx);
     if (!OK(status)) return status;
+
+/*
+** Assign the SPHANDLE address for the caller immediately to avoid timing issues with
+** WRTATTN AST that passes the ctx as rcvastprm (which sp_once does).
+*/
+    *ctxpp = ctx;
     ctx->sendque.head = ctx->sendque.tail = &ctx->sendque;
     ctx->ok_to_send = 0;
 
@@ -302,7 +310,6 @@ unsigned int sp_open (SPHANDLE *ctxpp, void *inicmd, unsigned int (*rcvast)(void
     str$free1_dx(&inbox);
     str$free1_dx(&outbox);
 
-    *ctxpp = ctx;
     return SS$_NORMAL;
 
 } /* sp_open */
@@ -526,7 +533,32 @@ void sp_once (void *cmd, void (*actrtn)(void *, struct dsc$descriptor *),
     }
     str$free1_dx(&eomcmd);
 } /* sp_once */
-
+
+/*
+**++
+**  ROUTINE:	sp_once_ast
+**
+**  FUNCTIONAL DESCRIPTION:
+**
+**
+**  RETURNS:	cond_value, longword (unsigned), write only, by value
+**
+**  PROTOTYPE:
+**
+**  	sp_once(struct ONCE *ctx)
+**
+**  IMPLICIT INPUTS:	None.
+**
+**  IMPLICIT OUTPUTS:	None.
+**
+**  COMPLETION CODES:
+**  	    SS$_NORMAL:  normal successful completion
+**  	    SS$_NONEXPR: subprocess doesn't exist any more
+**
+**  SIDE EFFECTS:   	None.
+**
+**--
+*/
 static unsigned int sp_once_ast(void *once) {
 
     struct ONCE *ctx = once;
@@ -536,15 +568,13 @@ static unsigned int sp_once_ast(void *once) {
     while (OK(sp_receive(&ctx->spctx, &rcvstr, 0))) {
         if (rcvstr.dsc$w_length > ctx->eom_len &&
                 strncmp(rcvstr.dsc$a_pointer, ctx->eom, ctx->eom_len) == 0) {
-            str$free1_dx(&rcvstr);
             ctx->command_complete = 1;
             sys$wake(0,0);
             break;
         }
         (ctx->actrtn)(ctx->param, &rcvstr);
-        str$free1_dx(&rcvstr);
     }
-    // str$free1_dx(&rcvstr);
+    str$free1_dx(&rcvstr);
     return SS$_NORMAL;
 } /* sp_once_ast */