(main): Fix the stack-limit code to calculate

the ratio for re_max_failures accurately and leave some extra slack.

1 files changed, 10 insertions, 4 deletions

diff --git a/src/emacs.c b/src/emacs.c
index 5a2ac8504c8..7e43d6ad949 100644
--- a/src/emacs.c
+++ b/src/emacs.c
@@ -595,8 +595,14 @@ main (argc, argv, envp)
     {
       long newlim;
       extern int re_max_failures;
-      /* Approximate the amount regex.c needs, plus some more.  */
-      newlim = re_max_failures * 2 * 20 * sizeof (char *);
+      /* Approximate the amount regex.c needs per unit of re_max_failures.  */
+      int ratio = 20 * sizeof (char *);
+      /* Then add 33% to cover the size of the smaller stacks that regex.c
+         successively allocates and discards, on its way to the maximum.  */
+      ratio += ratio / 3;
+      /* Add in some extra to cover
+         what we're likely to use for other reasons.  */
+      newlim = re_max_failures * ratio + 200000;
 #ifdef __NetBSD__
       /* NetBSD (at least NetBSD 1.2G and former) has a bug in its
        stack allocation routine for new process that the allocation
@@ -607,8 +613,8 @@ main (argc, argv, envp)
       if (newlim > rlim.rlim_max)
         {
           newlim = rlim.rlim_max;
-          /* Don't let regex.c overflow the stack.  */
-          re_max_failures = newlim / (2 * 20 * sizeof (char *));
+          /* Don't let regex.c overflow the stack we have.  */
+          re_max_failures = (newlim - 200000) / ratio;
         }
       if (rlim.rlim_cur < newlim)
         rlim.rlim_cur = newlim;