From 316e6894d6d432be763593b2e8ff816f413264dd Mon Sep 17 00:00:00 2001
From: Helmut Eller <eller.helmut@gmail.com>
Date: Fri, 24 May 2024 15:49:23 +0200
Subject: [PATCH 1/2] For igc_xpalloc_exact, make PA an in-out parameter

Because igc_xpalloc_exact uses mps_arena_release the scan_area callback
may be called before igc_xpalloc_exact returns.  With an in-out
parameter, the client has the option to receive the new address before
the igc_xpalloc_exact returns.

* src/igc.h (igc_xpalloc_exact): Change the type of PA.
* src/igc.c (igc_xpalloc_exact): Implement the new protocol.
* src/print.c (grow_pp_stack, grow_print_stack): Update accordingly.
---
 src/igc.c   | 11 ++++++-----
 src/igc.h   |  6 +++---
 src/print.c |  8 ++++----
 3 files changed, 13 insertions(+), 12 deletions(-)

diff --git a/src/igc.c b/src/igc.c
index dc4512713f7..4f22221e952 100644
--- a/src/igc.c
+++ b/src/igc.c
@@ -2416,13 +2416,14 @@ scan_xpalloced (mps_ss_t ss, void *start, void *end, void *closure)
   return scan_area ((struct igc_opaque *)ss, start, end, scan_cell);
 }
 
-void *
-igc_xpalloc_exact (void *pa, ptrdiff_t *nitems, ptrdiff_t nitems_incr_min,
-		   ptrdiff_t nitems_max, ptrdiff_t item_size,
-		   igc_scan_area_t scan_area)
+void
+igc_xpalloc_exact (void **pa_cell, ptrdiff_t *nitems,
+		   ptrdiff_t nitems_incr_min, ptrdiff_t nitems_max,
+		   ptrdiff_t item_size, igc_scan_area_t scan_area)
 {
   IGC_WITH_PARKED (global_igc)
   {
+    void *pa = *pa_cell;
     if (pa)
       {
 	struct igc_root_list *r = root_find (pa);
@@ -2433,8 +2434,8 @@ igc_xpalloc_exact (void *pa, ptrdiff_t *nitems, ptrdiff_t nitems_incr_min,
     char *end = (char *)pa + *nitems * item_size;
     root_create (global_igc, pa, end, mps_rank_exact (),
 		 scan_xpalloced, scan_area, false);
+    *pa_cell = pa;
   }
-  return pa;
 }
 
 void *
diff --git a/src/igc.h b/src/igc.h
index fb37ce22e22..5b97787916c 100644
--- a/src/igc.h
+++ b/src/igc.h
@@ -84,9 +84,9 @@ #define EMACS_IGC_H
 typedef igc_scan_result_t (*igc_scan_area_t) (struct igc_opaque *,
 					      void *start, void *end,
 					      igc_scan_cell_t fun);
-void *igc_xpalloc_exact (void *pa, ptrdiff_t *nitems,
-			 ptrdiff_t nitems_incr_min, ptrdiff_t nitems_max,
-			 ptrdiff_t item_size, igc_scan_area_t scan);
+void igc_xpalloc_exact (void **pa_cell, ptrdiff_t *nitems,
+			ptrdiff_t nitems_incr_min, ptrdiff_t nitems_max,
+			ptrdiff_t item_size, igc_scan_area_t scan);
 
 void *igc_xnrealloc_ambig (void *pa, ptrdiff_t nitems, ptrdiff_t item_size);
 
diff --git a/src/print.c b/src/print.c
index c87597be899..5aec73c15e3 100644
--- a/src/print.c
+++ b/src/print.c
@@ -1359,8 +1359,8 @@ grow_pp_stack (void)
   struct print_pp_stack *ps = &ppstack;
   eassert (ps->sp == ps->size);
 #ifdef HAVE_MPS
-  ps->stack = igc_xpalloc_exact (ps->stack, &ps->size, 1, -1,
-				 sizeof *ps->stack, scan_ppstack);
+  igc_xpalloc_exact ((void **)&ppstack.stack, &ps->size, 1, -1,
+		     sizeof *ps->stack, scan_ppstack);
 #else
   ps->stack = xpalloc (ps->stack, &ps->size, 1, -1, sizeof *ps->stack);
 #endif
@@ -2273,8 +2273,8 @@ grow_print_stack (void)
   struct print_stack *ps = &prstack;
   eassert (ps->sp == ps->size);
 #ifdef HAVE_MPS
-  ps->stack = igc_xpalloc_exact (ps->stack, &ps->size, 1, -1,
-				 sizeof *ps->stack, scan_prstack);
+  igc_xpalloc_exact ((void **)&prstack.stack, &ps->size, 1, -1,
+		     sizeof *ps->stack, scan_prstack);
 #else
   ps->stack = xpalloc (ps->stack, &ps->size, 1, -1, sizeof *ps->stack);
 #endif
-- 
2.39.2