From b0d690331db157f53ac4a8bd9d4bb7513a561d90 Mon Sep 17 00:00:00 2001
From: Ian Lance Taylor <iant@golang.org>
Date: Wed, 24 Jan 2018 18:25:39 -0800
Subject: [PATCH] 	* mmap.c (backtrace_free_locked): Don't put more than
 16 entries 	on the free list.

Fixes #5
Fixes rust-lang/rust#29293
Fixes rust-lang/rust#37477
---
 mmap.c | 24 +++++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/mmap.c b/mmap.c
index 41bbc71..32fcba6 100644
--- a/mmap.c
+++ b/mmap.c
@@ -69,11 +69,33 @@ struct backtrace_freelist_struct
 static void
 backtrace_free_locked (struct backtrace_state *state, void *addr, size_t size)
 {
-  /* Just leak small blocks.  We don't have to be perfect.  */
+  /* Just leak small blocks.  We don't have to be perfect.  Don't put
+     more than 16 entries on the free list, to avoid wasting time
+     searching when allocating a block.  If we have more than 16
+     entries, leak the smallest entry.  */
+
   if (size >= sizeof (struct backtrace_freelist_struct))
     {
+      size_t c;
+      struct backtrace_freelist_struct **ppsmall;
+      struct backtrace_freelist_struct **pp;
       struct backtrace_freelist_struct *p;
 
+      c = 0;
+      ppsmall = NULL;
+      for (pp = &state->freelist; *pp != NULL; pp = &(*pp)->next)
+	{
+	  if (ppsmall == NULL || (*pp)->size < (*ppsmall)->size)
+	    ppsmall = pp;
+	  ++c;
+	}
+      if (c >= 16)
+	{
+	  if (size <= (*ppsmall)->size)
+	    return;
+	  *ppsmall = (*ppsmall)->next;
+	}
+
       p = (struct backtrace_freelist_struct *) addr;
       p->next = state->freelist;
       p->size = size;