diff --git a/third_party/gmp/tal-debug.c b/third_party/gmp/tal-debug.c
new file mode 100644
index 0000000..38c27aa
--- /dev/null
+++ b/third_party/gmp/tal-debug.c
@@ -0,0 +1,150 @@
+/* TMP_ALLOC routines for debugging.
+
+Copyright 2000, 2001, 2004 Free Software Foundation, Inc.
+
+This file is part of the GNU MP Library.
+
+The GNU MP Library is free software; you can redistribute it and/or modify
+it under the terms of either:
+
+  * the GNU Lesser General Public License as published by the Free
+    Software Foundation; either version 3 of the License, or (at your
+    option) any later version.
+
+or
+
+  * the GNU General Public License as published by the Free Software
+    Foundation; either version 2 of the License, or (at your option) any
+    later version.
+
+or both in parallel, as here.
+
+The GNU MP Library is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received copies of the GNU General Public License and the
+GNU Lesser General Public License along with the GNU MP Library.  If not,
+see https://www.gnu.org/licenses/.  */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "gmp-impl.h"
+
+
+/* This method aims to help a malloc debugger find problems.  A linked list
+   of allocated block is kept for TMP_FREE to release.  This is reentrant
+   and thread safe.
+
+   Each TMP_ALLOC is a separate malloced block, so redzones or sentinels
+   applied by a malloc debugger either above or below can guard against
+   accesses outside the allocated area.
+
+   A marker is a "struct tmp_debug_t *" so that TMP_DECL can initialize it
+   to NULL and we can detect TMP_ALLOC without TMP_MARK.
+
+   It will work to realloc an MPZ_TMP_INIT variable, but when TMP_FREE comes
+   to release the memory it will have the old size, thereby triggering an
+   error from tests/memory.c.
+
+   Possibilities:
+
+   It'd be possible to keep a global list of active "struct tmp_debug_t"
+   records, so at the end of a program any TMP leaks could be printed.  But
+   if only a couple of routines are under test at any one time then the
+   likely culprit should be easy enough to spot.  */
+
+
+void
+__gmp_tmp_debug_mark (const char *file, int line,
+                      struct tmp_debug_t **markp, struct tmp_debug_t *mark,
+                      const char *decl_name, const char *mark_name)
+{
+  if (strcmp (mark_name, decl_name) != 0)
+    {
+      __gmp_assert_header (file, line);
+      fprintf (stderr, "GNU MP: TMP_MARK(%s) but TMP_DECL(%s) is in scope\n",
+               mark_name, decl_name);
+      abort ();
+    }
+
+  if (*markp != NULL)
+    {
+      __gmp_assert_header (file, line);
+      fprintf (stderr, "GNU MP: Repeat of TMP_MARK(%s)\n", mark_name);
+      if (mark->file != NULL && mark->file[0] != '\0' && mark->line != -1)
+        {
+          __gmp_assert_header (mark->file, mark->line);
+          fprintf (stderr, "previous was here\n");
+        }
+      abort ();
+    }
+
+  *markp = mark;
+  mark->file = file;
+  mark->line = line;
+  mark->list = NULL;
+}
+
+void *
+__gmp_tmp_debug_alloc (const char *file, int line, int dummy,
+                       struct tmp_debug_t **markp,
+                       const char *decl_name, size_t size)
+{
+  struct tmp_debug_t        *mark = *markp;
+  struct tmp_debug_entry_t  *p;
+
+  ASSERT_ALWAYS (size >= 1);
+
+  if (mark == NULL)
+    {
+      __gmp_assert_header (file, line);
+      fprintf (stderr, "GNU MP: TMP_ALLOC without TMP_MARK(%s)\n", decl_name);
+      abort ();
+    }
+
+  p = __GMP_ALLOCATE_FUNC_TYPE (1, struct tmp_debug_entry_t);
+  p->size = size;
+  p->block = (*__gmp_allocate_func) (size);
+  p->next = mark->list;
+  mark->list = p;
+  return p->block;
+}
+
+void
+__gmp_tmp_debug_free (const char *file, int line, int dummy,
+                      struct tmp_debug_t **markp,
+                      const char *decl_name, const char *free_name)
+{
+  struct tmp_debug_t        *mark = *markp;
+  struct tmp_debug_entry_t  *p, *next;
+
+  if (mark == NULL)
+    {
+      __gmp_assert_header (file, line);
+      fprintf (stderr, "GNU MP: TMP_FREE(%s) without TMP_MARK(%s)\n",
+               free_name, decl_name);
+      abort ();
+    }
+
+  if (strcmp (free_name, decl_name) != 0)
+    {
+      __gmp_assert_header (file, line);
+      fprintf (stderr, "GNU MP: TMP_FREE(%s) when TMP_DECL(%s) is in scope\n",
+               free_name, decl_name);
+      abort ();
+    }
+
+  p = mark->list;
+  while (p != NULL)
+    {
+      next = p->next;
+      (*__gmp_free_func) (p->block, p->size);
+      __GMP_FREE_FUNC_TYPE (p, 1, struct tmp_debug_entry_t);
+      p = next;
+    }
+
+  *markp = NULL;
+}