From d8b37824b5f3ea3d024911419559f4dfc7e8e40b Mon Sep 17 00:00:00 2001
From: Alexander Bolodurin <alexander.bolodurin@gmail.com>
Date: Sat, 1 Mar 2014 18:49:20 +1100
Subject: [PATCH] Remove dead stack-checking code.

Code under HAVE_STACK_LIMIT is not used.
The definition was commented out in rev 180 of the original
Mercurial repo, and then completely removed in rev 2520,
but the code guarded by it was left in.
---
 src/os_unix.c | 117 --------------------------------------------------
 src/os_unix.h |   1 -
 2 files changed, 118 deletions(-)

diff --git a/src/os_unix.c b/src/os_unix.c
index 4456a1110f..80832024c9 100644
--- a/src/os_unix.c
+++ b/src/os_unix.c
@@ -397,105 +397,6 @@ void mch_delay(long msec, int ignoreinput)
     WaitForChar(msec);
 }
 
-#if defined(HAVE_STACK_LIMIT) \
-  || (!defined(HAVE_SIGALTSTACK) && defined(HAVE_SIGSTACK))
-# define HAVE_CHECK_STACK_GROWTH
-/*
- * Support for checking for an almost-out-of-stack-space situation.
- */
-
-/*
- * Return a pointer to an item on the stack.  Used to find out if the stack
- * grows up or down.
- */
-static void check_stack_growth(char *p);
-static int stack_grows_downwards;
-
-/*
- * Find out if the stack grows upwards or downwards.
- * "p" points to a variable on the stack of the caller.
- */
-static void check_stack_growth(char *p)
-{
-  int i;
-
-  stack_grows_downwards = (p > (char *)&i);
-}
-#endif
-
-#if defined(HAVE_STACK_LIMIT) || defined(PROTO)
-static char *stack_limit = NULL;
-
-#if defined(_THREAD_SAFE) && defined(HAVE_PTHREAD_NP_H)
-# include <pthread.h>
-# include <pthread_np.h>
-#endif
-
-/*
- * Find out until how var the stack can grow without getting into trouble.
- * Called when starting up and when switching to the signal stack in
- * deathtrap().
- */
-static void get_stack_limit()                 {
-  struct rlimit rlp;
-  int i;
-  long lim;
-
-  /* Set the stack limit to 15/16 of the allowable size.  Skip this when the
-   * limit doesn't fit in a long (rlim_cur might be "long long"). */
-  if (getrlimit(RLIMIT_STACK, &rlp) == 0
-      && rlp.rlim_cur < ((rlim_t)1 << (sizeof(long_u) * 8 - 1))
-#  ifdef RLIM_INFINITY
-      && rlp.rlim_cur != RLIM_INFINITY
-#  endif
-      ) {
-    lim = (long)rlp.rlim_cur;
-#if defined(_THREAD_SAFE) && defined(HAVE_PTHREAD_NP_H)
-    {
-      pthread_attr_t attr;
-      size_t size;
-
-      /* On FreeBSD the initial thread always has a fixed stack size, no
-       * matter what the limits are set to.  Normally it's 1 Mbyte. */
-      pthread_attr_init(&attr);
-      if (pthread_attr_get_np(pthread_self(), &attr) == 0) {
-        pthread_attr_getstacksize(&attr, &size);
-        if (lim > (long)size)
-          lim = (long)size;
-      }
-      pthread_attr_destroy(&attr);
-    }
-#endif
-    if (stack_grows_downwards) {
-      stack_limit = (char *)((long)&i - (lim / 16L * 15L));
-      if (stack_limit >= (char *)&i)
-        /* overflow, set to 1/16 of current stack position */
-        stack_limit = (char *)((long)&i / 16L);
-    } else   {
-      stack_limit = (char *)((long)&i + (lim / 16L * 15L));
-      if (stack_limit <= (char *)&i)
-        stack_limit = NULL;             /* overflow */
-    }
-  }
-}
-
-/*
- * Return FAIL when running out of stack space.
- * "p" must point to any variable local to the caller that's on the stack.
- */
-int mch_stackcheck(char *p)
-{
-  if (stack_limit != NULL) {
-    if (stack_grows_downwards) {
-      if (p < stack_limit)
-        return FAIL;
-    } else if (p > stack_limit)
-      return FAIL;
-  }
-  return OK;
-}
-#endif
-
 #if defined(HAVE_SIGALTSTACK) || defined(HAVE_SIGSTACK)
 /*
  * Support for using the signal stack.
@@ -697,13 +598,6 @@ deathtrap SIGDEFARG(sigarg) {
   /* Set the v:dying variable. */
   set_vim_var_nr(VV_DYING, (long)entered);
 
-#ifdef HAVE_STACK_LIMIT
-  /* Since we are now using the signal stack, need to reset the stack
-   * limit.  Otherwise using a regexp will fail. */
-  get_stack_limit();
-#endif
-
-
 #ifdef SIGHASARG
   /* try to find the name of this signal */
   for (i = 0; signal_info[i].sig != -1; i++)
@@ -1531,17 +1425,6 @@ int mch_nodetype(char_u *name)
 }
 
 void mch_early_init()          {
-#ifdef HAVE_CHECK_STACK_GROWTH
-  int i;
-
-  check_stack_growth((char *)&i);
-
-# ifdef HAVE_STACK_LIMIT
-  get_stack_limit();
-# endif
-
-#endif
-
   /*
    * Setup an alternative stack for signals.  Helps to catch signals when
    * running out of stack space.
diff --git a/src/os_unix.h b/src/os_unix.h
index 79cabd0edf..02591f725f 100644
--- a/src/os_unix.h
+++ b/src/os_unix.h
@@ -5,7 +5,6 @@ void mch_write(char_u *s, int len);
 int mch_inchar(char_u *buf, int maxlen, long wtime, int tb_change_cnt);
 int mch_char_avail(void);
 void mch_delay(long msec, int ignoreinput);
-int mch_stackcheck(char *p);
 void mch_startjmp(void);
 void mch_endjmp(void);
 void mch_didjmp(void);