From 1b8128cf56f005fce2dee155f7ec0c10132be8b6 Mon Sep 17 00:00:00 2001
From: Ian Lance Taylor <iant@golang.org>
Date: Tue, 17 Apr 2018 10:59:18 -0700
Subject: [PATCH] 	* backtrace.c: Revert last change.  Don't call mmap 
 directly.

Updates #13
---
 backtrace.c | 44 +++++++++++---------------------------------
 1 file changed, 11 insertions(+), 33 deletions(-)

diff --git a/backtrace.c b/backtrace.c
index 319edcf..f8e3dc5 100644
--- a/backtrace.c
+++ b/backtrace.c
@@ -32,26 +32,12 @@ POSSIBILITY OF SUCH DAMAGE.  */
 
 #include "config.h"
 
-#include <unistd.h>
 #include <sys/types.h>
 
-#if !BACKTRACE_USES_MALLOC
-#include <sys/mman.h>
-#endif
-
 #include "unwind.h"
 #include "backtrace.h"
-#include "backtrace-supported.h"
 #include "internal.h"
 
-#ifndef MAP_ANONYMOUS
-#define MAP_ANONYMOUS MAP_ANON
-#endif
-
-#ifndef MAP_FAILED
-#define MAP_FAILED ((void *)-1)
-#endif
-
 /* The main backtrace_full routine.  */
 
 /* Data passed through _Unwind_Backtrace.  */
@@ -118,6 +104,7 @@ backtrace_full (struct backtrace_state *state, int skip,
 		backtrace_error_callback error_callback, void *data)
 {
   struct backtrace_data bdata;
+  void *p;
 
   bdata.skip = skip + 1;
   bdata.state = state;
@@ -126,25 +113,16 @@ backtrace_full (struct backtrace_state *state, int skip,
   bdata.data = data;
   bdata.ret = 0;
 
-#if !BACKTRACE_USES_MALLOC
-  {
-    size_t pagesize;
-    void *page;
-
-    /* If we can't allocate any memory at all, don't try to produce
-       file/line information.  */
-    pagesize = getpagesize ();
-    page = mmap (NULL, pagesize, PROT_READ | PROT_WRITE, 
-		 MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
-    if (page == MAP_FAILED)
-      bdata.can_alloc = 0;
-    else
-      {
-	munmap (page, pagesize);
-	bdata.can_alloc = 1;
-      }
-  }
-#endif
+  /* If we can't allocate any memory at all, don't try to produce
+     file/line information.  */
+  p = backtrace_alloc (state, 4096, NULL, NULL);
+  if (p == NULL)
+    bdata.can_alloc = 0;
+  else
+    {
+      backtrace_free (state, p, 4096, NULL, NULL);
+      bdata.can_alloc = 1;
+    }
 
   _Unwind_Backtrace (unwind, &bdata);
   return bdata.ret;