fis-gtm/sr_port/alias_funcs.c

/****************************************************************
 *								*
 *	Copyright 2009, 2011 Fidelity Information Services, Inc	*
 *								*
 *	This source code contains the intellectual property	*
 *	of its copyright holder(s), and is made available	*
 *	under a license.  If you do not know the terms of	*
 *	the license, please stop and do not read further.	*
 *								*
 ****************************************************************/

#include "mdef.h"

#include "gtm_stdio.h"
#include "gtm_string.h"

#include <stddef.h>

#include "rtnhdr.h"
#include "stack_frame.h"
#include "op.h"
#include "stp_parms.h"
#include "lv_val.h"
#include "error.h"
#include "buddy_list.h"		/* needed for tp.h */
#include "hashtab_int4.h"	/* needed for tp.h */
#include "gdsroot.h"
#include "gdsblk.h"
#include "gtm_facility.h"
#include "fileinfo.h"
#include "gdsbt.h"
#include "gdsfhead.h"
#include "gdskill.h"
#include "gdscc.h"
#include "filestruct.h"
#include "jnl.h"		/* needed for tp.h */
#include "tp.h"
#include "tp_frame.h"
#include "mv_stent.h"
#include "alias.h"
#include "gtm_malloc.h"
#include "stringpool.h"
#include "mmemory.h"

/* Define macros locally used by this routine only. General use macros are defined in alias.h */

/* Macro to decrement a base var reference. This lightweight version (of DECR_BASE_REF) used by "als_check_xnew_var_aliases"
 * is used to bypass most of the the LV_FREESLOT/LV_FLIST_ENQUEUE macro and do only reference count maint since the entire
 * symtab and all its lv_vals (lv_blks) are going to be released shortly.
 */
#define DECR_BASE_REF_LIGHT(lvp)					\
{	/* Perform reference count maintenance for base var */		\
	lvTree	*lvt_child;						\
									\
	assert(LV_IS_BASE_VAR(lvp));					\
	assert(0 < (lvp)->stats.trefcnt);				\
	DECR_TREFCNT(lvp);						\
	assert((lvp)->stats.trefcnt >= (lvp)->stats.crefcnt);		\
	if (0 == (lvp)->stats.trefcnt)					\
	{								\
		(lvp)->v.mvtype = 0;					\
		lvt_child = LV_GET_CHILD(lvp);				\
		if (lvt_child)						\
		{							\
			LV_CHILD(lvp) = NULL;				\
			als_xnew_killaliasarray(lvt_child);		\
		}							\
	}								\
}

/* Macro to decrement an alias container reference. This lightweight version used by "als_check_xnew_var_aliases"
 * is used to bypass the DECR_BASE_REF_NOSYM macro invocation (in most cases) and do only reference count maint
 * since the entire symtab and all its lv_vals (lv_blks) are going to be released shortly. Note this macro is
 * known to only be used on subscripted nodes hence the additional initial assert.
 */
#define DECR_AC_REF_LIGHT(LVP)									\
{												\
	symval	*lvp_sym, *lvref_sym;								\
	lv_val	*lvp_base;									\
												\
	assert(!LV_IS_BASE_VAR(LVP));								\
	if (MV_ALIASCONT & (LVP)->v.mvtype)							\
	{	/* Killing an alias container, perform reference count maintenance */ 		\
		lv_val	*lvref = (lv_val *)(LVP)->v.str.addr;					\
		assert(lvref);									\
		assert(LV_IS_BASE_VAR(lvref));							\
		assert(0 == (LVP)->v.str.len);							\
		assert(0 < lvref->stats.crefcnt);						\
		assert(0 < lvref->stats.trefcnt);						\
		DECR_CREFCNT(lvref);								\
		lvref_sym = LV_GET_SYMVAL(lvref);						\
		lvp_base = LV_GET_BASE_VAR(LVP);						\
		lvp_sym = LV_GET_SYMVAL(lvp_base);						\
		if (lvref_sym == lvp_sym)							\
		{	/* pointed to lvval owned by popd symval, use light flavor */		\
			DECR_BASE_REF_LIGHT(lvref);						\
		} else										\
		{	/* pointed to lvval owned by other symval, use full flavor */		\
			DECR_BASE_REF_NOSYM(lvref, TRUE);					\
		}										\
	}											\
}

/* Macro to mark an lv_val as reachable and process its descendants if any.
 * Note that like the _CNTNRS_IN_TREE macros, in dbg mode, we will scan the array
 * for containers even if has_aliascont flag is FALSE.
 */
#define MARK_REACHABLE(lvp)										\
{													\
	lvTree	*lvt;											\
	symval	*sym;											\
													\
	assert((lvp));											\
	/* Since this macro can be called in cases where the lv_val is NOT valid, such as in		\
	 * the case an MVST_PVAL mv_stent entry with an mvs_val entry that has been deleted		\
	 * by alias reassignment (see unw_mv_ent), we need to verify we have an actual lv_val		\
	 * by the same methods used to build the lv_val list and only then check if this		\
	 * lv_val has been processed yet.								\
	 */												\
	sym = LV_SYMVAL(lvp);										\
	if ((NULL != sym) && SYM_IS_SYMVAL(sym) && ((lvp)->stats.lvtaskcycle != lvtaskcycle))		\
	{	/* This lv_val has not been processed yet */						\
		DBGRFCT((stderr, "\nMARK_REACHABLE: Marking lv 0x"lvaddr" as reachable\n",		\
			 (lvp)));									\
		(lvp)->stats.lvtaskcycle = lvtaskcycle;		/* Mark it */				\
		if ((NULL != (lvt = LV_GET_CHILD(lvp))) PRO_ONLY(&& (lvp)->has_aliascont))		\
		{	/* And it has descendents to process */						\
			DBGRFCT((stderr, "MARK_REACHABLE: Scanning same lv for containers\n"));		\
			als_prcs_markreached_cntnr(lvt);						\
		}											\
	}												\
}

/* Macro to clone an lv_val */
#define CLONE_LVVAL(oldlv, newlv, cursymval)		\
{							\
	assert(LV_IS_BASE_VAR(oldlv));			\
	newlv = lv_getslot(cursymval);			\
	*newlv = *oldlv;				\
	LV_SYMVAL(newlv) = cursymval;			\
	lv_var_clone(newlv, newlv);			\
	oldlv->v.mvtype = MV_LVCOPIED;			\
	oldlv->ptrs.copy_loc.newtablv = newlv;		\
}

/* Macro to initialize a ZWR_ZAV_BLK structure */
#define ZAV_BLK_INIT(zavb, zavbnext)											\
	(zavb)->next = (zavbnext);											\
	(zavb)->zav_base = (zavb)->zav_free = (zwr_alias_var *)((char *)(zavb) + SIZEOF(zwr_zav_blk));			\
	(zavb)->zav_top = (zwr_alias_var *)((char *)(zavb)->zav_base + (SIZEOF(zwr_alias_var) * ZWR_ZAV_BLK_CNT));

/* Macro to run a given tree looking for container vars. Process what they point to in order to make sure what they point to
 * doesn't live in the symbol tree being popped. If so, move to the current tree (copying if necessary). If what is being pointed
 * to was not passed through then it will not be put into the symbol table but will instead just be data pointed to by the
 * container var. Like the _CNTNRS_IN_TREE macros, in dbg mode, we will scan the array for containers even if has_aliascont
 * flag is FALSE.
 */
#define RESOLV_ALIAS_CNTNRS_IN_TREE(LV_BASE, POPDSYMVAL, CURSYMVAL)					\
{													\
	lvTree	*lvt;											\
													\
	if ((NULL != (lvt = LV_GET_CHILD(LV_BASE))) && ((LV_BASE)->stats.lvtaskcycle != lvtaskcycle)	\
		PRO_ONLY(&& (LV_BASE)->has_aliascont))							\
	{												\
		(LV_BASE)->stats.lvtaskcycle = lvtaskcycle;						\
		als_prcs_xnew_alias_cntnr(lvt, POPDSYMVAL, CURSYMVAL);					\
	}												\
}

GBLREF stack_frame	*frame_pointer;
GBLREF symval		*curr_symval;
GBLREF unsigned char	*msp, *stackbase, *stacktop, *stackwarn;
GBLREF mv_stent		*mv_chain;
GBLREF tp_frame		*tp_pointer;
GBLREF zwr_hash_table	*zwrhtab;
GBLREF trans_num	local_tn;					/* transaction number for THIS PROCESS */
GBLREF uint4		tstartcycle;
GBLREF uint4		lvtaskcycle;					/* lv_val cycle for misc lv_val related tasks */
GBLREF mstr		**stp_array;
GBLREF int		stp_array_size;
GBLREF lv_val		*zsrch_var, *zsrch_dir1, *zsrch_dir2;
GBLREF tp_frame		*tp_pointer;
GBLREF int4		SPGC_since_LVGC;				/* stringpool GCs since the last dead-data GC */
GBLREF boolean_t	suspend_lvgcol;
GBLREF lv_xnew_var	*xnewvar_anchor;
GBLREF lv_xnew_ref	*xnewref_anchor;
GBLREF mval		*alias_retarg;

LITREF mname_entry	null_mname_entry;

/* Local routines -- not made static so they show up in pro core stack traces */
STATICFNDCL void als_xnew_killaliasarray(lvTree *lvt);
STATICFNDCL void als_prcs_xnew_alias_cntnr(lvTree *lvt, symval *popdsymval, symval *cursymval);
STATICFNDCL void als_prcs_markreached_cntnr(lvTree *lvt);

CONDITION_HANDLER(als_check_xnew_var_aliases_ch);


/***************************************************************************************/

/* Routine to repair the l_symtab entries in the stack due to hash table expansion such that the
 * l_symtab entries no longer point to valid hash table entries.
 *
 * Note that the "repair" done by this routine depends on the special processing done in
 * expand_hashtab_mname (EXPAND_HASHTAB rtn in hashtab_implementation.h) which does not free the
 * old table and places the addresses of the new hash table entries in the the value of the old
 * hash table entries. This allows this routine to access the old table with the existing
 * l_symtab entries and pull the new values that should be put in the respective l_symtab
 * entries before it completes the cleanup and releases the old hash table.
 *
 * Operation - Loop through the stack and:
 *
 * 1) For each unique l_symtab, run through the entries in the l_symtab.
 * 2) If entry is null, skip.
 * 3) If entry falls within range of the old symbol table, load the address in it and verify
 *    that it falls within the range of the new symbol table.
 * 4) If the entry does not fall within the range of the old symtab:
 *    a) Stop the search as we must have run into an older symtab
 *    b) If debug, assert fail if this is not the first_symbol in this l_symtab we have seen
 *       since an l_symtab can only point to one symtab).
 * 5) Get new entry address from within the old entry.
 * 6) Debug only: Assert fail if the new entry address not in range of new symtab.
 * 7) Note that after procesing the stack to get to the l_symtab entries, we also process the
 *    mv_stent types that contain hash table entry pointers and have to be processed in the same
 *    fashion as the l_symtab entries. This processing saves us the hashtable lookup necessary to
 *    pop NEW'd or parameter values when undoing a stack level and restoring previous values.
 */
void als_lsymtab_repair(hash_table_mname *table, ht_ent_mname *table_base_orig, int table_size_orig)
{
	int			htcnt;
	boolean_t		done;
	mv_stent 		*mv_st_ent;
	ht_ent_mname		*table_top_orig, **last_lsym_hte, **htep, *htenew;
	stack_frame		*fp, *fpprev;
	DEBUG_ONLY(boolean_t	first_sym;)

	assert(table);
	assert(table_base_orig);
	assert(table_base_orig != curr_symval->h_symtab.base);
	table_top_orig = table_base_orig + table_size_orig;
	last_lsym_hte = NULL;
	done = FALSE;
	fp = frame_pointer;
	assert(frame_pointer);
	do
	{	/* Once through for each stackframe using the same symbol table. Note this loop is similar
		 * to the stack frame loop in op_clralsvars.c.
		 */
		if (fp->l_symtab != last_lsym_hte)
		{	/* Different l_symtab than last time (don't want to update twice) */
			last_lsym_hte = fp->l_symtab;
			if (htcnt = fp->vartab_len)	/* Note assignment */
			{	/* Only process non-zero length l_symtabs */
				DEBUG_ONLY(first_sym = TRUE);
				for (htep = fp->l_symtab; htcnt; --htcnt, ++htep)
				{
					if (NULL == *htep)
						continue;
					if (*htep < table_base_orig || *htep >= table_top_orig)
					{	/* Entry doesn't point to the current symbol table */
						assert(first_sym);
						done = TRUE;
						break;
					}
					htenew = (ht_ent_mname *)((*htep)->value);	/* Pick up entry we should now use */
					assert(htenew >= table->base && htenew < (table->base + table->size));
					*htep = htenew;
					DEBUG_ONLY(first_sym = FALSE);
				}
			}
		}
		fpprev = fp;
		fp = fp->old_frame_pointer;
		if (done)
			break;
		if (SFF_CI & fpprev->flags)
		{	/* Callins needs to be able to crawl past apparent end of stack to earlier stack segments.
			 * We should be in the base frame now. See if an earlier frame exists.
			 * Note we don't worry about trigger base frames here because triggers *always* have a
			 * different symbol table - previous symbol tables and stack levels are not affected.
			 */
			fp = *(stack_frame **)(fp + 1);	/* Backups up to "prev pointer" created by base_frame() */
			if (NULL == fp || fp >= (stack_frame *)stackbase || fp < (stack_frame *)stacktop)
				break;	/* Pointer not within the stack -- must be earliest occurence */
		}
	} while(fp);
	/* Next, check the mv_stents for the stackframes we processed. Certain mv_stents also have hash
	 * table references in them that need repair.
	 */
	for (mv_st_ent = mv_chain;
	     mv_st_ent < (mv_stent *)(fp ? fp : fpprev);	/* Last stack frame actually processed */
	     mv_st_ent = (mv_stent *)(mv_st_ent->mv_st_next + (char *)mv_st_ent))
	{
		switch (mv_st_ent->mv_st_type)
		{	/* The types processed here contain hash table pointers that need to be modified */
			case MVST_NTAB:
				htep = &mv_st_ent->mv_st_cont.mvs_ntab.hte_addr;
				break;
			case MVST_PVAL:
				htep = &mv_st_ent->mv_st_cont.mvs_pval.mvs_ptab.hte_addr;
				break;
			case MVST_NVAL:
				htep = &mv_st_ent->mv_st_cont.mvs_nval.mvs_ptab.hte_addr;
				break;
			default:
				continue;
		}
		if (NULL == *htep)
			continue;
		if (*htep < table_base_orig || *htep >= table_top_orig)
			/* Entry doesn't point to the current symbol table so ignore it since it didn't change */
			continue;
		htenew = (ht_ent_mname *)((*htep)->value);	/* Pick up entry we should now use */
		assert(htenew >= table->base && htenew < (table->base + table->size));
		*htep = htenew;
	}
	/* For debug at least make unusable in case any stragglers point to it -- even though we are somewhat duplicating
	 * the SmInitAlloc gtmdgblvl flag here, this is so critical for debugging we want to do this even when general
	 * checking is not being done. SE 09/2008
	 */
	DEBUG_ONLY(memset(table_base_orig, 0xfe, table_size_orig * SIZEOF(ht_ent_mname)));
}

/* Local routine! condition handler whose sole function is to turn off the flag that says we are in "als_check_xnew_var_alias" */
CONDITION_HANDLER(als_check_xnew_var_aliases_ch)
{
	START_CH;
	suspend_lvgcol = FALSE;
	NEXTCH;
}

/* When an xNEW'd symtab is popped, and there are alias concerns, this routine is called to make things right. Things that
 * can be wrong:
 * 1) If a variable was passed through to the new symtab and then was aliased to a var that belonged to the new symbol table,
 *    the lv_val in the old symtab was released and a new one assigned in the new symbol table. We have to:
 *    a) copy that value back to the previous symtab and
 *    b) we have to fix the reference count since the alias owned by the new symtab is going away.
 * 2) If a variable is passed through to the new symtab and within that variable an alias container is created that points
 *    to a var in the newer symtab we need to copy that var/array back to the older symtab so the value remains.
 * 3) This gets more interesting to deal with when that var is also aliased by a passed through variable (combining issues 1 & 2).
 *
 * Operation:
 * 1) When the new symtab was created by op_xnew, if there were variables that were passed through, they are recorded in the
 *    symtab chained from xnew_var_list.
 * 2) Go through that list of variables, lookup each in the popped symbol table and change the hash table entries to deleted
 *    so those entries are not found in subsequent scans.
 * 3) Do a more simplistic kill-alias-all in the popped symtab. This involves the following:
 *    a) Run the hash table looking for aliased variables. If found, do the reference count maintenance but don't worry about
 *       deleting any data since it will all go away after we return and unw_mv_ent() releases the symbol table and lv_blk chains.
 *    b) While running the hash table, run any variable trees we find anchored.
 * 4) Go through the list of forwarded vars again (xnew_var_list) in the popped symval and see if any of the lv_vals are owned
 *    by the symval being popped. If they are, then the lv_vals involved need to be copied to lv_vals owned by the (now)
 *    current symtab because the popped symtab's lv_vals will be released by unw_mv_ent() when we return. Note that this also
 *    involves going through the tree of these vars in case any container vars point to an array that is not being dealt with
 *    in some fashion by one of the other vars we passed through. We avoid processing arrays multiple times by marking them
 *    with an incremented lvtaskval.
 * 5) Go through the list of referenced lv_vals (via containers of xnew_var_list vars) by traversing the xnew_ref_list if it
 *    exists. These vars were recorded because we may not be able to get to them still just by traversing the reference list vars
 *    so they were pre-recorded so we could scan the worst case of vars that could have containers pointing to the symtab about
 *    to be popped.
 * 6) If a pending alias return value exists, check it to see if it also needs to be processed.
 *
 *    Note: to prevent re-scanning of already scanned array, this routine uses the lvtaskcycle value. To do this, we use the
 *    suspend_lvgcol global variable to tell "stp_gcol" to not do LVGC processing (which also uses lvtaskcycle).
 */
void als_check_xnew_var_aliases(symval *popdsymval, symval *cursymval)
{
	lv_xnew_var		*xnewvar, *xnewvar_next;
	lv_xnew_ref		*xnewref, *xnewref_next;
	ht_ent_mname    	*tabent;
	hash_table_mname	*popdsymtab, *cursymtab;
	ht_ent_mname		*htep, *htep_top;
	lv_val			*lv, *prevlv, *currlv, *popdlv;
	lv_val			*newlv, *oldlv;
	boolean_t		bypass_lvscan, bypass_lvrepl;
	DBGRFCT_ONLY(mident_fixed vname;)

	ESTABLISH(als_check_xnew_var_aliases_ch);
	suspend_lvgcol = TRUE;
	assert(NULL != popdsymval);
	assert(NULL != cursymval);
	assert((NULL != popdsymval->xnew_var_list) || (NULL != alias_retarg));

	DBGRFCT((stderr, "\nals_check_xnew_var_aliases: Beginning xvar pop processing\n"));
	/* Step 2: (step 1 done in op_xnew()) - Run the list of vars that were passed through the xnew and remove them
	 * from the popped hash table so they can not be found by the step 3 scan below - meaning we won't mess with the
	 * reference counts of these entries but we will record their locations so we can process them in step 4.
	 */
	popdsymtab = &popdsymval->h_symtab;
	cursymtab = &cursymval->h_symtab;
	for (xnewvar = popdsymval->xnew_var_list; xnewvar; xnewvar = xnewvar->next)
	{
		tabent = lookup_hashtab_mname(popdsymtab, &xnewvar->key);
		assert(tabent);
		xnewvar->lvval = (lv_val *)tabent->value;	/* Cache lookup results for 2nd pass in step 4 */
		delete_hashtab_ent_mname(popdsymtab, tabent);
	}
	/* Step 3: Run popped hash table undoing alias references. */
	DBGRFCT((stderr, "als_check_xnew_var_aliases: Step 3 - running popped symtab tree undoing local refcounts\n"));
	for (htep = popdsymtab->base, htep_top = popdsymtab->top; htep < htep_top; htep++)
	{
		if (HTENT_VALID_MNAME(htep, lv_val, lv))
			DECR_BASE_REF_LIGHT(lv);
	}
	/* Step 4: See what, if anything, needs to be copied from popped level to current level. There are 3 possible
	 * cases here. Note in all cases, we must decrement the use counters of prevlv since they were incremented in
	 * op_xnew to keep things from disappearing prematurely (we don't want the LVs we saved to be scrapped and re-used
	 * so we make sure they stay around).
	 *
	 * Vars used:
	 *
	 *   prevlv == lv from the current symbol table.
	 *   currlv == lv we are going to eventually put into the current symbol table
	 *   popdlv == lv from the popped symbol table
	 *
	 * Cases follow:
	 *
	 *    Condition						Action
	 *
	 * a) prevlv == popdlv					Scan prevlv for alias containers pointing to popped symtab.
	 * b) prevlv != popdlv && popdlv in popd symtab.	Clone popdlv into currlv & do alias container scan.
	 * c) prevlv != popdlv && popdlv not in popd symtab.	Same as case (a). Note this includes the case where popdlv
	 *                                                      already resides in cursymtab.
	 */
	DBGRFCT((stderr, "als_check_xnew_var_aliases: Step 4 - beginning unwind scan of passed through vars\n"));
	INCR_LVTASKCYCLE;
	for (xnewvar = popdsymval->xnew_var_list; xnewvar; xnewvar = xnewvar_next)
	{
		bypass_lvscan = bypass_lvrepl = FALSE;
		tabent = lookup_hashtab_mname(cursymtab, &xnewvar->key);
		assert(tabent);				/* Had better be there since it was passed in thru the exclusive new */
		DBGRFCT_ONLY(
			memcpy(vname.c, tabent->key.var_name.addr, tabent->key.var_name.len);
			vname.c[tabent->key.var_name.len] = '\0';
		);
		prevlv = (lv_val *)tabent->value;
		popdlv = xnewvar->lvval;		/* Value of this var in popped symtab */
		DBGRFCT((stderr, "als_check_xnew_var_aliases: var '%s' prevlv: 0x"lvaddr" popdlv: 0x"lvaddr"\n",
			 &vname.c, prevlv, popdlv));
		if (prevlv == popdlv)
		{	/* Case (a) - Just do the scan below */
			currlv = prevlv;
			bypass_lvrepl = TRUE;
		} else if (popdsymval == LV_GET_SYMVAL(popdlv))
		{	/* Case (b) - Clone the var and tree into blocks owned by current symtab with the caveat that we need not
			 * do this if the array has already been cloned (because more than one var that was passed through it
			 * pointing to it.
			 */
			if (MV_LVCOPIED == popdlv->v.mvtype)
			{	/* This lv_val has been copied over already so use that pointer instead to put into the
				 * current hash table.
				 */
				currlv = popdlv->ptrs.copy_loc.newtablv;
				assert(LV_GET_SYMVAL(currlv) == cursymval);
				bypass_lvscan = TRUE;	/* lv_val would have already been scanned */
				DBGRFCT((stderr, "als_check_xnew_var_aliases: lv already copied so setting currlv to 0x"lvaddr"\n",
					 currlv));
			} else
			{
				assert(LV_IS_BASE_VAR(popdlv));
				/* lv_val is owned by the popped symtab .. clone it to the new current tree */
				CLONE_LVVAL(popdlv, currlv, cursymval);
				DBGRFCT((stderr, "als_check_xnew_var_aliases: lv has been cloned from 0x"lvaddr" to 0x"lvaddr"\n",
					 popdlv, currlv));
			}
		} else
		{	/* Case (c) - same as (a) except we do replace the lv in cursymtab */
			assert(LV_IS_BASE_VAR(popdlv));
			currlv = popdlv;
		}
		if (!bypass_lvscan)
		{	/* Need to run this tree (if any) to look for container vars buried within */
			DBGRFCT((stderr, "als_check_xnew_var_aliases: potentially scanning lv 0x"lvaddr"\n", currlv));
			RESOLV_ALIAS_CNTNRS_IN_TREE(currlv, popdsymval, cursymval);
		}
		if (1 < prevlv->stats.trefcnt)
			/* If prevlv is going to be around after we drop op_xnew's refcnt bumps, make sure it gets processed.
			 * If it was processed above, then it is marked such and the macro will bypass processing it again.
			 */
			RESOLV_ALIAS_CNTNRS_IN_TREE(prevlv, popdsymval, cursymval);
		DECR_CREFCNT(prevlv);		/* undo bump by op_xnew */
		if (!bypass_lvrepl)
		{	/* Replace the lvval in the current symbol table */
			DBGRFCT((stderr, "als_check_xnew_var_aliases: Resetting variable '%s' hte at 0x"lvaddr" from 0x"lvaddr
				 " to 0x"lvaddr"\n", &vname.c, tabent, prevlv, currlv));
			tabent->value = (void *)currlv;
		}
		assert(1 <= prevlv->stats.trefcnt);	/* verify op_xnew's bump is still there (may be only one) */
		DECR_BASE_REF_NOSYM(prevlv, TRUE);	/* undo bump by op_xnew */
		xnewvar_next = xnewvar->next;
		xnewvar->next = xnewvar_anchor;
		xnewvar_anchor = xnewvar;
	}
	/* Step 5: See if anything on the xnew_ref_list needs to be handled */
	DBGRFCT((stderr, "als_check_xnew_var_aliases: Step 5: Process xnew_ref_list if any\n"));
	for (xnewref = popdsymval->xnew_ref_list; xnewref; xnewref = xnewref_next)
	{
		prevlv = xnewref->lvval;
		DBGRFCT((stderr, "als_check_xnew_var_aliases:  xnewref-prevlv: 0x"lvaddr"\n", prevlv));
		DECR_CREFCNT(prevlv);		/* Will remove the trefcnt in final desposition below */
		/* Only do the scan if the reference count is greater than 1 since we are going to remove the
		 * refcnts added by op_xnew as we finish here. So if the var is going away anyway, no need
		 * to scan.
		 */
		if (1 < prevlv->stats.trefcnt)
		{	/* Process the array */
			DBGRFCT((stderr, "als_check_xnew_var_aliases: potentially scanning lv 0x"lvaddr"\n", prevlv));
			RESOLV_ALIAS_CNTNRS_IN_TREE(prevlv, popdsymval, cursymval);
		} else
			DBGRFCT((stderr, "als_check_xnew_var_aliases: prevlv was deleted\n"));
		/* Remove refcnt and we are done */
		DECR_BASE_REF_NOSYM(prevlv, TRUE);
		xnewref_next = xnewref->next;
		xnewref->next = xnewref_anchor;
		xnewref_anchor = xnewref;
	}
	/* Step 6: Check if a pending alias return value exists and if so if it needs to be processed.
	 *         This type of value is created by unw_retarg() as the result of a "QUIT *" statement. It is an alias container
	 *	   mval that lives in the compiler temps of the caller with a pointer in an mv_stent of the callee in the mvs_parm
	 *	   block allocated by push_parm. Since this mval-container is just an mval and not an lv_val, we have to largely
	 *         do similar processing to the "als_prcs_xnew_alias_cntnr" with this block type difference in mind.
	 */
	if (NULL != alias_retarg)
	{
		assert(0 != (MV_ALIASCONT & alias_retarg->mvtype));
		oldlv = (lv_val *)alias_retarg->str.addr;
		if (MV_LVCOPIED == oldlv->v.mvtype)
		{	/* This lv_val has been copied over already so use that pointer instead */
			newlv = oldlv->ptrs.copy_loc.newtablv;
			alias_retarg->str.addr = (char *)newlv;			/* Replace container ptr */
			DBGRFCT((stderr, "\nals_check_xnew_var_aliases: alias retarg var found - referenced array already copied"
				 " - Setting pointer in aliascont mval 0x"lvaddr" to lv 0x"lvaddr"\n", alias_retarg, newlv));
		} else
		{
			assert(LV_IS_BASE_VAR(oldlv));
			if (popdsymval == LV_SYMVAL(oldlv))
			{	/* lv_val is owned by the popped symtab .. clone it to the new current tree */
				CLONE_LVVAL(oldlv, newlv, cursymval);
				alias_retarg->str.addr = (char *)newlv;		/* Replace container ptr */
				DBGRFCT((stderr, "\nals_check_xnew_var_aliases: alias retarg var found - aliascont mval 0x"lvaddr
					 " being reset to point to lv 0x"lvaddr" which is a clone of lv 0x"lvaddr"\n",
					 alias_retarg, newlv, oldlv));
			} else
			{	/* lv_val is owned by current or older symval .. just use it in the subsequent scan in case it
				 * leads us to other lv_vals owned by the popped symtab.
				 */
				DBGRFCT((stderr, "\nals_check_xnew_var_aliases: alias retarg var found - aliascont mval 0x"lvaddr
				 " just being (potentially) scanned for container vars\n", alias_retarg));
				newlv = oldlv;
			}
			RESOLV_ALIAS_CNTNRS_IN_TREE(newlv, popdsymval, cursymval);
		}
	}
	DBGRFCT((stderr, "als_check_xnew_var_aliases: Completed xvar pop processing\n"));
	suspend_lvgcol = FALSE;
	REVERT;
}

/* Local routine!
 * This routine is basically a slightly lightweight lv_killarray() that goes through a given tree looking for container vars
 * and performing the necessary reference count cleanup as well as freeing the lv tree nodes but wont go through the
 * bother of hashtable maintenance since the hashtable is anyways going away as part of the symbol table pop.
 */
STATICFNDEF void als_xnew_killaliasarray(lvTree *lvt)
{
	lvTreeNode	*node, *nextnode;
	lvTree		*tmplvt;

	DEBUG_ONLY(
		lv_val		*lv;

		assert(NULL != lvt);
		lv = (lv_val *)LVT_PARENT(lvt);
		assert(NULL == LV_CHILD(lv));	/* Owner lv's children pointer MUST be NULL! */
			/* See comment in lv_killarray for why this is necessary */
	)
	/* Iterate through the tree in post-order fashion. Doing it in-order or pre-order has issues since we would have
	 * freed up nodes in the tree but would need to access links in them to get at the NEXT node.
	 */
	for (node = lvAvlTreeFirstPostOrder(lvt); NULL != node; node = nextnode)
	{
		nextnode = lvAvlTreeNextPostOrder(node);	/* determine "nextnode" before freeing "node" */
		assert(NULL != node);
		tmplvt = LV_CHILD(node);
		if (NULL != tmplvt)
		{
			LV_CHILD(node) = NULL;
			als_xnew_killaliasarray(tmplvt);
		}
		DECR_AC_REF_LIGHT(((lv_val *)node));	/* Decrement alias contain ref and cleanup if necessary */
		/* If node points to an "lv_val", we need to do a heavyweight LV_FREESLOT call to free up the lv_val.
		 * But we instead do a simple "LVTREENODE_FREESLOT" call because we are guaranteed node points to a "lvTreeNode"
		 * (i.e. it is a subscripted lv and never the base lv). Assert that.
		 */
		assert(!LV_IS_BASE_VAR(node));
		LVTREENODE_FREESLOT(node);
	}
	LVTREE_FREESLOT(lvt);
}

/* Local routine!
 * Routine to process an alias container found in a node of a var being "returned" back through an exclusive new.
 * We may have to move the data.
 */
STATICFNDEF void als_prcs_xnew_alias_cntnr(lvTree *lvt, symval *popdsymval, symval *cursymval)
{
	lvTree		*lvt_child;
	lvTreeNode	*node;
	lv_val		*newlv, *oldlv;

	assert(NULL != lvt);	/* caller should not call if no subtree */
	/* In the case of lv_killarray, the only option we have is to do post-order traversal since we are freeing
	 * nodes in the tree as we traverse. But in this case, we dont change the tree structure so we are free to
	 * choose any order. We choose in-order as that is faster than post-order.
	 */
	for (node = lvAvlTreeFirst(lvt); NULL != node; node = lvAvlTreeNext(node))
	{
		if (node->v.mvtype & MV_ALIASCONT)
		{
			assert(lvt->base_lv->has_aliascont);
			assert(!LV_IS_BASE_VAR(node));
			oldlv = (lv_val *)node->v.str.addr;
			assert(NULL != oldlv);
			assert(LV_IS_BASE_VAR(oldlv));
			if (MV_LVCOPIED == oldlv->v.mvtype)
			{	/* This lv_val has been copied over already so use that pointer instead */
				newlv = oldlv->ptrs.copy_loc.newtablv;
				assert(LV_IS_BASE_VAR(newlv));
				node->v.str.addr = (char *)newlv;			/* Replace container ptr */
				DBGRFCT((stderr, "\nals_prcs_xnew_alias_cntnr: aliascont var found - referenced array already "
					 "copied - Setting pointer in aliascont lv 0x"lvaddr" to lv 0x"lvaddr"\n", node, newlv));
			} else
			{
				assert(LV_IS_BASE_VAR(oldlv));
				if (popdsymval == LV_SYMVAL(oldlv))
				{	/* lv_val is owned by the popped symtab .. clone it to the new current tree */
					CLONE_LVVAL(oldlv, newlv, cursymval);
					assert(LV_IS_BASE_VAR(newlv));
					node->v.str.addr = (char *)newlv;		/* Replace container ptr */
					DBGRFCT((stderr, "\nals_prcs_xnew_alias_cntnr: aliascont var found - aliascont lv 0x"lvaddr
						 " being reset to point to lv 0x"lvaddr" which is a clone of lv 0x"lvaddr"\n", node,
						 newlv, oldlv));
				} else
				{	/* lv_val is owned by current or older symval .. just use it in the subsequent scan in case
					 * it leads us to other lv_vals owned by the popped symtab. */
					DBGRFCT((stderr, "\nals_prcs_xnew_alias_cntnr: aliascont var found - aliascont lv 0x"lvaddr
						 " just being (potentially) scanned for container vars\n", node));
					newlv = oldlv;
				}
				RESOLV_ALIAS_CNTNRS_IN_TREE(newlv, popdsymval, cursymval);
			}
		}
		lvt_child = LV_GET_CHILD(node);
		if (NULL != lvt_child)	/* Descend recursively down this tree as well */
			als_prcs_xnew_alias_cntnr(lvt_child, popdsymval, cursymval);
	}
}

/* Routine to process an alias container found in an array being "saved" by TSTART (op_tstart). We need to set this array up
 * so it gets copied just like op_tstart does for the base variables that are specified in it. In addition, this new array
 * itself needs to be scanned so if it points to anything, that too gets saved if modified (all handled by
 * TP_SAVE_RESTART_VAR macro).
 */
void als_prcs_tpsav_cntnr(lvTree *lvt)
{
	lvTree		*lvt_child;
	lvTreeNode	*node;
	lv_val		*cntnr_lv_base;

	assert(NULL != lvt);	/* caller should not call if no subtree */
	/* In the case of lv_killarray, the only option we have is to do post-order traversal since we are freeing
	 * nodes in the tree as we traverse. But in this case, we dont change the tree structure so we are free to
	 * choose any order. We choose in-order as that is faster than post-order.
	 */
	for (node = lvAvlTreeFirst(lvt); NULL != node; node = lvAvlTreeNext(node))
	{
		if (node->v.mvtype & MV_ALIASCONT)
		{
			assert(lvt->base_lv->has_aliascont);
			assert(!LV_IS_BASE_VAR(node));
			cntnr_lv_base = (lv_val *)node->v.str.addr;	/* Extract container pointer */
			assert(NULL != cntnr_lv_base);
			assert(LV_IS_BASE_VAR(cntnr_lv_base));
			assert(1 <= cntnr_lv_base->stats.trefcnt);
			assert(1 <= cntnr_lv_base->stats.crefcnt);
			if (NULL == cntnr_lv_base->tp_var)
			{	/* Save this var if it hasn't already been saved */
				assert(cntnr_lv_base->stats.tstartcycle != tstartcycle);
				DBGRFCT((stderr, "\ntpSAV_container: Container at 0x"lvaddr
					" refers to lv 0x"lvaddr" -- Creating tpsav block\n", node, cntnr_lv_base));
				TP_SAVE_RESTART_VAR(cntnr_lv_base, tp_pointer, &null_mname_entry);
				INCR_CREFCNT(cntnr_lv_base);	/* 2nd increment for reference via a container node */
				INCR_TREFCNT(cntnr_lv_base);
				if (LV_HAS_CHILD(cntnr_lv_base))
					TPSAV_CNTNRS_IN_TREE(cntnr_lv_base);
			} else
			{	/* If not saving it, we still need to bump the ref count(s) for this reference and
				 * process any children if we have't already seen this node (taskcycle check will tell us this).
				 */
				DBGRFCT((stderr, "\ntpSAV_container: Container at 0x"lvaddr" refers to lv 0x"lvaddr
					" -- Incrementing refcnts\n", node, cntnr_lv_base));
				INCR_CREFCNT(cntnr_lv_base);
				INCR_TREFCNT(cntnr_lv_base);
				assert(0 < cntnr_lv_base->stats.trefcnt);
				assert(0 < cntnr_lv_base->stats.crefcnt);
				if (cntnr_lv_base->stats.tstartcycle != tstartcycle)
				{
					DBGRFCT((stderr, "\ntpSAV_container: .. Container at 0x"lvaddr" refers to lv 0x"lvaddr
						 " -- processing tree\n", node, cntnr_lv_base));
					if (LV_HAS_CHILD(cntnr_lv_base))
						TPSAV_CNTNRS_IN_TREE(cntnr_lv_base);
				} else
				{
					DBGRFCT((stderr, "\ntpSAV_container: .. Container at 0x"lvaddr" refers to lv 0x"lvaddr
						 " -- Already processed -- bypassing\n", node, cntnr_lv_base));
				}
			}
		}
		lvt_child = LV_GET_CHILD(node);
		if (NULL != lvt_child)	/* Descend recursively down this tree as well */
			als_prcs_tpsav_cntnr(lvt_child);
	}
}

/* For a given container var found in the tree  we need to re-establish the reference counts for the base var
 * the container is pointing to. Used during a local var restore on a TP restart.
 */
void als_prcs_tprest_cntnr(lvTree *lvt)
{
	lvTree		*lvt_child;
	lvTreeNode	*node;
	lv_val		*cntnr_lv_base;

	assert(NULL != lvt);	/* caller should not call if no subtree */
	/* In the case of lv_killarray, the only option we have is to do post-order traversal since we are freeing
	 * nodes in the tree as we traverse. But in this case, we dont change the tree structure so we are free to
	 * choose any order. We choose in-order as that is faster than post-order.
	 */
	for (node = lvAvlTreeFirst(lvt); NULL != node; node = lvAvlTreeNext(node))
	{
		if (node->v.mvtype & MV_ALIASCONT)
		{
			assert(lvt->base_lv->has_aliascont);
			assert(!LV_IS_BASE_VAR(node));
			cntnr_lv_base = (lv_val *)node->v.str.addr;	/* Extract container pointer */
			assert(NULL != cntnr_lv_base);
			assert(LV_IS_BASE_VAR(cntnr_lv_base));
			assert(1 <= cntnr_lv_base->stats.trefcnt);
			assert(1 <= cntnr_lv_base->stats.crefcnt);
			assert(cntnr_lv_base->tp_var);
			DBGRFCT((stderr, "\ntpREST_cntnr_node: Processing container at 0x"lvaddr"\n", node));
			INCR_CREFCNT(cntnr_lv_base);
			INCR_TREFCNT(cntnr_lv_base);
			assert(0 < (cntnr_lv_base)->stats.trefcnt);
			assert(0 < (cntnr_lv_base)->stats.crefcnt);
		}
		lvt_child = LV_GET_CHILD(node);
		if (NULL != lvt_child)	/* Descend recursively down this tree as well */
			als_prcs_tprest_cntnr(lvt_child);
	}
}

/* For a given container, decrement the ref count of the creature it points to. Part of unwinding an unmodified
 * tp saved variable.
 */
void als_prcs_tpunwnd_cntnr(lvTree *lvt)
{
	lvTree		*lvt_child;
	lvTreeNode	*node;
	lv_val		*cntnr_lv_base;

	assert(NULL != lvt);	/* caller should not call if no subtree */
	/* In the case of lv_killarray, the only option we have is to do post-order traversal since we are freeing
	 * nodes in the tree as we traverse. But in this case, we dont change the tree structure so we are free to
	 * choose any order. We choose in-order as that is faster than post-order.
	 */
	for (node = lvAvlTreeFirst(lvt); NULL != node; node = lvAvlTreeNext(node))
	{
		if (node->v.mvtype & MV_ALIASCONT)
		{
			assert(lvt->base_lv->has_aliascont);
			assert(!LV_IS_BASE_VAR(node));
			cntnr_lv_base = (lv_val *)node->v.str.addr;	/* Extract container pointer */
			assert(NULL != cntnr_lv_base);
			assert(LV_IS_BASE_VAR(cntnr_lv_base));
			assert(1 <= cntnr_lv_base->stats.trefcnt);
			assert(1 <= cntnr_lv_base->stats.crefcnt);
			/* Note we cannot assert cntnr_lv_base->tp_var here since the tp_var node may have already been freed and
			 * cleared by unwind processing of the base var itself. We just have to undo our counts here and keep going.
			 */
			DBGRFCT((stderr, "\ntpUNWND_cntnr_node: Processing container at 0x"lvaddr"\n", cntnr_lv_base));
			DECR_CREFCNT(cntnr_lv_base);
			DECR_BASE_REF_NOSYM(cntnr_lv_base, FALSE);
		}
		lvt_child = LV_GET_CHILD(node);
		if (NULL != lvt_child)	/* Descend recursively down this tree as well */
			als_prcs_tpunwnd_cntnr(lvt_child);
	}
}

/* This routine deletes the data pointed to by the lv_val and removes the container flag from the value making it just
 * a regular NULL/0 value.
 */
void als_prcs_kill_cntnr(lvTree *lvt)
{
	lvTree		*lvt_child;
	lvTreeNode	*node;
	lv_val		*cntnr_lv_base;

	assert(NULL != lvt);	/* caller should not call if no subtree */
	/* In the case of lv_killarray, the only option we have is to do post-order traversal since we are freeing
	 * nodes in the tree as we traverse. But in this case, we dont change the tree structure so we are free to
	 * choose any order. We choose in-order as that is faster than post-order.
	 */
	for (node = lvAvlTreeFirst(lvt); NULL != node; node = lvAvlTreeNext(node))
	{
		if (node->v.mvtype & MV_ALIASCONT)
		{
			assert(lvt->base_lv->has_aliascont);
			assert(!LV_IS_BASE_VAR(node));
			cntnr_lv_base = (lv_val *)node->v.str.addr;
			assert(NULL != cntnr_lv_base);
			assert(LV_IS_BASE_VAR(cntnr_lv_base));
			node->v.mvtype &= ~MV_ALIASCONT;
			DECR_CREFCNT(cntnr_lv_base);
			DECR_BASE_REF_NOSYM(cntnr_lv_base, TRUE);
		}
		lvt_child = LV_GET_CHILD(node);
		if (NULL != lvt_child)	/* Descend recursively down this tree as well */
			als_prcs_kill_cntnr(lvt_child);
	}
}

/* Local routine!
 * This routine checks if the supplied container points to an lv_val that is already marked as having been processd in this pass.
 * If not, the lv_val is marked and processed recursively.
 */
STATICFNDEF void als_prcs_markreached_cntnr(lvTree *lvt)
{
	lvTree		*lvt_child;
	lvTreeNode	*node;
	lv_val		*cntnr_lv_base;

	assert(NULL != lvt);	/* caller should not call if no subtree */
	/* In the case of lv_killarray, the only option we have is to do post-order traversal since we are freeing
	 * nodes in the tree as we traverse. But in this case, we dont change the tree structure so we are free to
	 * choose any order. We choose in-order as that is faster than post-order.
	 */
	for (node = lvAvlTreeFirst(lvt); NULL != node; node = lvAvlTreeNext(node))
	{
		if (node->v.mvtype & MV_ALIASCONT)
		{
			assert(lvt->base_lv->has_aliascont);
			assert(!LV_IS_BASE_VAR(node));
			cntnr_lv_base = (lv_val *)node->v.str.addr;
			assert(NULL != cntnr_lv_base);
			assert(LV_IS_BASE_VAR(cntnr_lv_base));
			MARK_REACHABLE(cntnr_lv_base);
		}
		lvt_child = LV_GET_CHILD(node);
		if (NULL != lvt_child)	/* Descend recursively down this tree as well */
			als_prcs_markreached_cntnr(lvt_child);
	}
}

/* Function to scan an lvval for containers pointing to other structures that need to be scanned in xnew pop processing.
 * This goes through the entire tree of lv nodes looking for containers and if it finds any, it finds the base var pointed
 * to by the container if it has not already been processed in this pass (as determined by lvtaskcycle). Processing includes
 * incrementing refcnts and creating an lv_xnew_ref entry for the base var so we can check it again when the symtab pops to
 * see if any containers were created in them that point to the symtab being popped.
 */
void als_prcs_xnewref_cntnr(lvTree *lvt)
{
	lvTree		*lvt_child;
	lvTreeNode	*node;
	lv_val		*cntnr_lv_base;
	lv_xnew_ref	*xnewref;

	assert(NULL != lvt);	/* caller should not call if no subtree */
	/* In the case of lv_killarray, the only option we have is to do post-order traversal since we are freeing
	 * nodes in the tree as we traverse. But in this case, we dont change the tree structure so we are free to
	 * choose any order. We choose in-order as that is faster than post-order.
	 */
	for (node = lvAvlTreeFirst(lvt); NULL != node; node = lvAvlTreeNext(node))
	{
		if (node->v.mvtype & MV_ALIASCONT)
		{
			assert(lvt->base_lv->has_aliascont);
			assert(!LV_IS_BASE_VAR(node));
			cntnr_lv_base = (lv_val *)node->v.str.addr;
			assert(NULL != cntnr_lv_base);
			assert(LV_IS_BASE_VAR(cntnr_lv_base));
			if (cntnr_lv_base->stats.lvtaskcycle != lvtaskcycle)
			{
				INCR_CREFCNT(cntnr_lv_base);
				INCR_TREFCNT(cntnr_lv_base);
				cntnr_lv_base->stats.lvtaskcycle = lvtaskcycle;
				if (NULL != xnewref_anchor)
				{	/* Reuse entry from list */
					xnewref = xnewref_anchor;
					xnewref_anchor = xnewref->next;
				} else
				{	/* Malloc an entry. Note that these blocks are put back on the chain anchored at the
					 * xnewref_anchor global in function "als_check_xnew_var_aliases". They are not freed
					 * since xnews typically happen in subroutines for temporary periods making the
					 * likelihood of block reuse high. Also they are small and typically few in number.
					 */
					xnewref = (lv_xnew_ref *)malloc(SIZEOF(lv_xnew_ref));
				}
				xnewref->lvval = cntnr_lv_base;
				xnewref->next = curr_symval->xnew_ref_list;
				curr_symval->xnew_ref_list = xnewref;
				if (LV_HAS_CHILD(cntnr_lv_base))
					XNEWREF_CNTNRS_IN_TREE(cntnr_lv_base);
			}
		}
		lvt_child = LV_GET_CHILD(node);
		if (NULL != lvt_child)	/* Descend recursively down this tree as well */
			als_prcs_xnewref_cntnr(lvt_child);
	}
}

/* Initialize ZWRite hash table structures used when ZWRiting in an aliased variable environment */
void als_zwrhtab_init(void)
{
	zwr_zav_blk	*zavb, *zavb_next;

	if (zwrhtab && zwrhtab->cleaned)
		return;
	if (NULL == zwrhtab)
	{	/* none yet .. allocate and init one */
		zwrhtab = (zwr_hash_table *)malloc(SIZEOF(zwr_hash_table));
		zwrhtab->first_zwrzavb = NULL;
		init_hashtab_addr(&zwrhtab->h_zwrtab, ZWR_HTAB_INIT_SIZE, HASHTAB_COMPACT, HASHTAB_SPARE_TABLE);
	} else
	{	/* Have one, reinitialize it */
		assert(zwrhtab->first_zwrzavb);
		zavb = zwrhtab->first_zwrzavb;
		if (zavb)
		{
			for (zavb_next = zavb->next; zavb_next; zavb = zavb_next, zavb_next = zavb->next)
			{	/* Leave one block on queue if it exists .. get rid of others */
				free(zavb);
			}
			assert(zavb);
			zwrhtab->first_zwrzavb = zavb;
		}
		reinitialize_hashtab_addr(&zwrhtab->h_zwrtab);
	}
	if (NULL == zwrhtab->first_zwrzavb)
		zwrhtab->first_zwrzavb = (zwr_zav_blk *)malloc(SIZEOF(zwr_zav_blk) + (SIZEOF(zwr_alias_var) * ZWR_ZAV_BLK_CNT));
	ZAV_BLK_INIT(zwrhtab->first_zwrzavb, NULL);
	zwrhtab->cleaned = TRUE;
}

/* Obtain a zwr_alias_var slot for the zalias hash table */
zwr_alias_var *als_getzavslot(void)
{
	zwr_alias_var	*zav;
	zwr_zav_blk	*zavb;

	assert(zwrhtab);
	assert(zwrhtab->first_zwrzavb);

	zwrhtab->cleaned = FALSE;	/* No longer in a clean/initialized state */
	/* Check if a block can be allocated out of a zavb super block */
	zavb = zwrhtab->first_zwrzavb;
	assert(zavb);
	if (zavb->zav_free >= zavb->zav_top)
	{	/* This block is full too .. need a new one */
		zavb = (zwr_zav_blk *)malloc(SIZEOF(zwr_zav_blk) + (SIZEOF(zwr_alias_var) * ZWR_ZAV_BLK_CNT));
		ZAV_BLK_INIT(zavb, zwrhtab->first_zwrzavb);
		zwrhtab->first_zwrzavb = zavb;
	}
	assert(zavb->zav_free < zavb->zav_top);
	zav = zavb->zav_free++;
	zav->value_printed = FALSE;
	return zav;
}

/* See if lv_val is associated with a base named var in the current symval.
 * Scan the hash table for valid entries and see if any of them point to supplied lv_val.
 * If so, return the hash table entry which contains the var's name that is "lowest" which
 * necessitates a full scan of the hash table (which ZWrite processing is going to do several
 * times anyway.
 */
ht_ent_mname *als_lookup_base_lvval(lv_val *lvp)
{
	ht_ent_mname	*htep, *htep_top, *htep_loweq;
	lv_val		*lvhtval;

	assert(LV_IS_BASE_VAR(lvp));
	htep_loweq = NULL;
	htep = curr_symval->h_symtab.base;
	htep_top = curr_symval->h_symtab.base + curr_symval->h_symtab.size;
	assert(htep_top ==  curr_symval->h_symtab.top);
	for (; htep < htep_top; htep++)
	{
		if (HTENT_VALID_MNAME(htep, lv_val, lvhtval) && '$' != *htep->key.var_name.addr && lvp == lvhtval)
		{	/* HT entry is valid and has a key that is not a $ZWRTAC type key and the lval matches
			 * so we have a candidate to check for "lowest" alias name for given lv_val addr.
			 */
			if (htep_loweq)
			{	/* See current champ higher than candidate, then get new champ */
				if (0 < memvcmp(htep_loweq->key.var_name.addr, htep_loweq->key.var_name.len,
						htep->key.var_name.addr, htep->key.var_name.len))
					htep_loweq = htep;
			} else
				/* First time thru, free-ride assignment */
				htep_loweq = htep;
		}
	}
	return htep_loweq;
}

/* Routine to do a garbage collection on the lv_vals in the current symbol table in order to detect if
 * there is any "lost data" which are 2 or more base lv_vals that point to each other thus keeping their
 * reference counts non-zero and prevent them from being deleted but otherwise have no entry in the hash table
 * themselves nor are linked to by any combination of container var linked arrays that do have an entry in
 * the hash table -- in other words, they are totally orphaned with no way to retrieve them so are effectively
 * dead but are not able to be killed in an automated fashion. This routine will find and kill those blocks
 * returning a count of the lv_vals thus found and killed.
 *
 * Operation:
 *
 * 1)  Run lv_blks which contain all lv_val structures in use for this symbol table.
 * 2)  Record each base lv_val in our version of the array used by stp_gcol. Base lv_vals can be identified
 *     by having a non-zero parent.sym field pointing to a block with type MV_SYM. There are 3 exceptions to
       this: In UNIX, the zsearch_var, zsearch_dir1, and zsearch_dir2 fields contain lv_vals that should not be
       released. Check for and avoid them.
 * 3)  Increment lvtaskcycle with which we will mark lv_vals as having been marked accessible as we discover them.
 * 4)  Go through the hashtable. Set the lvtaskcycle field to mark the lv_val "reachable".
 * 5)  If the lv_val has descendants, run the decendant chain to look for container vars.
 * 6)  The base lv_vals that container vars point to, if not already marked "reachable"  will be so marked and
 *     the search recursively invoked on the new var.
 * 7)  Do the same by running the mv_stent chain marking the temporarily displaced vars for parameters and NEW's as
 *     "reachable".
 * 8)  Do the same by running the TP stack marking local variable copies made for this symbol table as reachable.
 * 9)  Mark any pending return argument as "reachable".
 * 10) Once the "reachable" search is complete, run through the created list of lv_vals and locate any that were
 *     not reachable. If they remain undeleted (deleted will have parent.sym field zeroed), delete them.
 *
 * Note this routine uses the same buffer structure that "stp_gcol" uses except it loads its array with lv_val*
 * instead of mstr*. An address is an address..
 */
int als_lvval_gc(void)
{
	int		killcnt;
	lv_blk		*lv_blk_ptr;
	ht_ent_mname	*htep, *htep_top;
	lv_val		*lvp, *lvlimit;
	lv_val		**lvarraycur, **lvarray, **lvarraytop, **lvptr;
	mv_stent 	*mv_st_ent;
	tp_frame	*tf;
	tp_var		*restore_ent;
	lvTree		*lvt_child;
	symval		*sym;
	DEBUG_ONLY(uint4 savelvtaskcycle;)
	DCL_THREADGBL_ACCESS;

	SETUP_THREADGBL_ACCESS;
	assert(!suspend_lvgcol);
	DBGRFCT((stderr, "als_lvval_gc: Beginning lv_val garbage collection\n"));
	if (NULL == stp_array)
		/* Same initialization as is in stp_gcol_src.h */
		stp_array = (mstr **)malloc((stp_array_size = STP_MAXITEMS) * SIZEOF(mstr *));

	lvarraycur = lvarray = (lv_val **)stp_array;
	lvarraytop = lvarraycur + stp_array_size;

	/* Steps 1,2 - find all the base lv_vals and put in list */
	for (lv_blk_ptr = curr_symval->lv_first_block; lv_blk_ptr; lv_blk_ptr = lv_blk_ptr->next)
	{
		for (lvp = (lv_val *)LV_BLK_GET_BASE(lv_blk_ptr), lvlimit = LV_BLK_GET_FREE(lv_blk_ptr, lvp);
		     lvp < lvlimit;  lvp++)
		{
			sym = LV_SYMVAL(lvp);
			assert((NULL == sym) || SYM_IS_SYMVAL(sym));
			if ((NULL != sym) UNIX_ONLY(&& (TREF(zsearch_var) != lvp))
					UNIX_ONLY(&& (TREF(zsearch_dir1) != lvp) && (TREF(zsearch_dir2) != lvp)))
			{	/* Put it in the list */
				assert(0 < lvp->stats.trefcnt);
				if (lvarraycur >= lvarraytop)
				{	/* Need more room -- expand */
					stp_expand_array();
					lvarraycur = lvarray = (lv_val **)stp_array;
					lvarraytop = lvarraycur + stp_array_size;
				}
				*lvarraycur++ = lvp;
			}
		}
	}
	/* Step 3, increment lvtaskcycle to mark "reachable" lv_vals */
	INCR_LVTASKCYCLE;
	DEBUG_ONLY(savelvtaskcycle = lvtaskcycle);
	/* Steps 4,5,6 - Find and mark reachable lv_vals */
	DBGRFCT((stderr, "als_lvval_gc: Starting symtab scan\n"));
	htep = curr_symval->h_symtab.base;
	htep_top = curr_symval->h_symtab.base + curr_symval->h_symtab.size;
	assert(htep_top == curr_symval->h_symtab.top);
	for (; htep < htep_top; htep++)
	{
		if (HTENT_VALID_MNAME(htep, lv_val, lvp))
		{	/* HT entry is valid. Note for purposes of this loop, we do NOT bypass $ZWRTAC type keys since
			 * they are valid reachable variables even if hidden */
			MARK_REACHABLE(lvp);
		}
	}
	/* Step 7 - Run the mv_stent chain marking those vars as reachable. */
	DBGRFCT((stderr, "als_lvval_gc: Starting mv_stent scan\n"));
	for (mv_st_ent = mv_chain; mv_st_ent; mv_st_ent = (mv_stent *)(mv_st_ent->mv_st_next + (char *)mv_st_ent))
	{
		switch (mv_st_ent->mv_st_type)
		{	/* The types processed here contain lv_vals we want to mark */
			case MVST_NTAB:
				lvp = mv_st_ent->mv_st_cont.mvs_ntab.save_value;
				DBGRFCT((stderr, "als_lvval_gc: NTAB at 0x"lvaddr" has save value 0x"lvaddr"\n",
					 mv_st_ent, lvp));
				assert(NULL != lvp);
				break;
			case MVST_PVAL:
				/* Note the save_value in the PVAL types below can be zero since they are created in
				 * op_bindparm with a NULL save_value value and later filled in by op_bindparm. It is
				 * possible to trigger this code in between the push_parm call of the caller and the
				 * op_bindparm call of the callee when tracing or with an outofband event. In that case,
				 * we don't want that NULL save_value pointer ending our loop prematurely.
				 */
				lvp = mv_st_ent->mv_st_cont.mvs_pval.mvs_ptab.save_value;
				DBGRFCT((stderr, "als_lvval_gc: PVAL at 0x"lvaddr" has save value 0x"lvaddr"\n",
					 mv_st_ent, lvp));
				assert(NULL != mv_st_ent->mv_st_cont.mvs_pval.mvs_val);
				/* Mark created lv_val to hold current value as reachable as it may not (yet) be in the
				 * hashtable if op_bindparm has not yet run.
				 */
				MARK_REACHABLE(mv_st_ent->mv_st_cont.mvs_pval.mvs_val);
				if (NULL == lvp)
					continue;	/* Don't end loop prematurely */
				break;
			case MVST_NVAL:
				lvp = mv_st_ent->mv_st_cont.mvs_nval.mvs_ptab.save_value;
				DBGRFCT((stderr, "als_lvval_gc: NVAL at 0x"lvaddr" has save value 0x"lvaddr"\n",
					 mv_st_ent, lvp));
				assert(NULL != mv_st_ent->mv_st_cont.mvs_nval.mvs_val);
				/* Mark created lv_val to hold current value as reachable as it may not (yet) be in the
				 * hashtable if op_bindparm has not yet run.
				 */
				MARK_REACHABLE(mv_st_ent->mv_st_cont.mvs_nval.mvs_val);
				assert(NULL != lvp);
				break;
			case MVST_STAB:
				/* The symbol table is changing to be other than the table we are using so we can
				 * stop the loop now. Exiting the switch with lvp NULL indicates that.
				 */
				DBGRFCT((stderr, "als_lvval_gc: STAB mv_stent at 0x"lvaddr" stops mv_stent scan\n",
					mv_st_ent));
				lvp = NULL;
				break;
			default:
				DBGRFCT((stderr, "als_lvval_gc: Ignoring mv_stent type %d\n", mv_st_ent->mv_st_type));
				continue;
		}
		if (NULL == lvp)
			break;
		MARK_REACHABLE(lvp);
	}
	/* Step 8 - Run the TP stack to see if there is anything we can mark reachable */
	DBGRFCT((stderr, "als_lvval_gc: Starting TP stack scan\n"));
	for (tf = tp_pointer; NULL != tf && tf->sym == curr_symval; tf = tf->old_tp_frame)
	{
		for (restore_ent = tf->vars;  NULL != restore_ent;  restore_ent = restore_ent->next)
		{	/* Since TP keeps its own use count on these sorts of variables, we will mark both the
			 * current and saved values in these blocks. This is because the "current value" could
			 * be detached from the hash table at this point but is still viable while we hold a use
			 * count on it.
			 */
			MARK_REACHABLE(restore_ent->current_value);
			MARK_REACHABLE(restore_ent->save_value);
		}
	}
	/* Step 9 - Mark any pending alias return argument as reachable */
	if (NULL != alias_retarg)
	{	/* There is a pending alias return arg (container). Find the lv it is pointing to and mark it and its progeny
		 * as reachable.
		 */
		assert(0 != (MV_ALIASCONT & alias_retarg->mvtype));
		lvp = (lv_val *)alias_retarg->str.addr;
		assert(LV_IS_BASE_VAR(lvp));
		MARK_REACHABLE(lvp);
	}
	/* Step 10 - Run the list of base lv_vals we created earlier and see which ones were not marked with the current
	 * cycle. Note they may have already been deleted after the first one gets deleted so we can check for that
	 * by looking for a zeroed parent field. Note the object of this code is not to force-delete the vars as we
	 * encounter them but by performing a deletion of their arrays, we will kill the interlinking container vars that
	 * are keeping these vars alive.
	 */
	killcnt = 0;
	DBGRFCT((stderr, "\nals_lvval_gc: final orphaned lvval scan\n"));
	for (lvptr = lvarray; lvptr < lvarraycur; ++lvptr)
	{
		lvp = *lvptr;
		if (lvp->stats.lvtaskcycle != lvtaskcycle)
		{	/* Have an orphaned lv_val */
			DBGRFCT((stderr, "\nals_lvval_gc: lvval 0x"lvaddr" has been identified as orphaned\n", lvp));
			++killcnt;
			if (LV_SYMVAL(lvp))
			{	/* Var is still intact, kill it. Note that in this situation, since there are no hash table
				 * entries pointing to us, our container refs and total refs should be equal. We can't
				 * use the "regular" DECR macros because those get us into trouble. For example if this
				 * var has a container pointing to another var who has a container pointing to us and it
				 * is only those pointers keeping both vars alive, decrementing our counter causes it to
				 * become zero which messes up the deletion of the other var's container since the refcnts
				 * are already zero. What we will do instead is INCREASE the trefcnt to keep this var from
				 * being deleted, then drive the kill of any array it has to spur these vars to go away.
				 */
				assert(LV_IS_BASE_VAR(lvp));
				DBGRFCT((stderr, "\nals_lvval_gc: Working to release unreachable lvval 0x"lvaddr"\n", lvp));
				assert(lvp->stats.trefcnt == lvp->stats.crefcnt);
				INCR_TREFCNT(lvp);
				lvt_child = LV_GET_CHILD(lvp);
				if (NULL != lvt_child)
				{
					assert(lvp == (lv_val *)LVT_PARENT(lvt_child));
					LV_CHILD(lvp) = NULL;
					lv_killarray(lvt_child, FALSE);
				}
				DECR_BASE_REF_NOSYM(lvp, FALSE); /* Var might go away now, or later if need more deletes first */
			} else
				DBGRFCT((stderr, "\nals_lvval_gc: Seems to have become released -- lvval 0x"lvaddr"\n", lvp));
		}
	}
	DBGRFCT((stderr, "\nals_lvval_gc: final orphaned lvval scan completed\n"));
#	ifdef DEBUG
	/* The removal of a reference for each lv_val should have done it but let's go back and verify they all
	 * went away. If not, then it is not a simple case of user silliness and we have a problem.
	 */
	for (lvptr = lvarray; lvptr < lvarraycur; ++lvptr)
	{
		lvp = *lvptr;
		if (lvp->stats.lvtaskcycle != lvtaskcycle && LV_SYMVAL(lvp))
		{	/* Var is still intact, kill it */
			assert(FALSE);
		}
	}
#	endif
	assert(lvtaskcycle == savelvtaskcycle);
	DBGRFCT((stderr, "als_lvval_gc: GC complete -- recovered %d lv_vals\n", killcnt));
	SPGC_since_LVGC = 0;
	return killcnt;
}

# ifdef DEBUG_ALIAS
/* Routine to check lv_val monitoring. If any lv_vals that were created during the monitoring period still exist, emit a
 * message to that effect with the lv_val address. In this manner we hope to find lv_val leaks (if any) in various tests.
 * Note that this is a debugging (not debug build) only routine since its costs are non-trivial and is only enabled
 * when necessary. Other tests check for memory leaks so if they find one, this monitoring can be used to discover the
 * source so this is not needed for test coverage.
 */
void als_lvmon_output(void)
{
	symval		*lvlsymtab;
	lv_blk		*lvbp;
	lv_val		*lvp, *lvp_top;

	flush_pio();
	for (lvlsymtab = curr_symval; lvlsymtab; lvlsymtab = lvlsymtab->last_tab)
	{
		for (lvbp = curr_symval->lv_first_block; lvbp; lvbp = lvbp->next)
		{
			for (lvp = (lv_val *)LV_BLK_GET_BASE(lvbp), lvp_top = LV_BLK_GET_FREE(lvbp, lvp); lvp < lvp_top; lvp++)
			{
				if (lvp->lvmon_mark)
				{	/* lv_val slot not used as an sbs and is marked. Report it */
					FPRINTF(stderr, "als_lvmon_output: lv_val at 0x"lvaddr" is still marked\n", lvp);
				}
			}
		}
	}
	fflush(stderr);
}
# endif