From 5529b1b183a2b2a51784fe6ee292bdf9032e8834 Mon Sep 17 00:00:00 2001
From: Remi Gacogne <remi.gacogne@powerdns.com>
Date: Wed, 6 Jun 2018 10:37:25 +0200
Subject: [PATCH] rec: Allocate one more stack byte to make _GLIBCXX_ASSERTIONS
 happy

---
 pdns/mtasker.cc          | 4 ++--
 pdns/mtasker_fcontext.cc | 6 +++---
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/pdns/mtasker.cc b/pdns/mtasker.cc
index 9fcb7d31f..16027b610 100644
--- a/pdns/mtasker.cc
+++ b/pdns/mtasker.cc
@@ -268,10 +268,10 @@ template<class Key, class Val>void MTasker<Key,Val>::makeThread(tfunc_t *start,
   auto uc=std::make_shared<pdns_ucontext_t>();
   
   uc->uc_link = &d_kernel; // come back to kernel after dying
-  uc->uc_stack.resize (d_stacksize);
+  uc->uc_stack.resize (d_stacksize+1);
 #ifdef PDNS_USE_VALGRIND
   uc->valgrind_id = VALGRIND_STACK_REGISTER(&uc->uc_stack[0],
-                                            &uc->uc_stack[uc->uc_stack.size()]);
+                                            &uc->uc_stack[uc->uc_stack.size()-1]);
 #endif /* PDNS_USE_VALGRIND */
 
   auto& thread = d_threads[d_maxtid];
diff --git a/pdns/mtasker_fcontext.cc b/pdns/mtasker_fcontext.cc
index 0ab87b6f6..72627a7e5 100644
--- a/pdns/mtasker_fcontext.cc
+++ b/pdns/mtasker_fcontext.cc
@@ -216,13 +216,13 @@ pdns_makecontext
     assert (ctx.uc_link);
     assert (ctx.uc_stack.size() >= 8192);
     assert (!ctx.uc_mcontext);
-    ctx.uc_mcontext = make_fcontext (&ctx.uc_stack[ctx.uc_stack.size()],
-                                     ctx.uc_stack.size(), &threadWrapper);
+    ctx.uc_mcontext = make_fcontext (&ctx.uc_stack[ctx.uc_stack.size()-1],
+                                     ctx.uc_stack.size()-1, &threadWrapper);
     args_t args;
     args.self = &ctx;
     args.work = &start;
     /* jumping to threadwrapper */
-    notifyStackSwitch(&ctx.uc_stack[ctx.uc_stack.size()], ctx.uc_stack.size());
+    notifyStackSwitch(&ctx.uc_stack[ctx.uc_stack.size()-1], ctx.uc_stack.size()-1);
 #if BOOST_VERSION < 106100
     jump_fcontext (reinterpret_cast<fcontext_t*>(&args.prev_ctx),
                    static_cast<fcontext_t>(ctx.uc_mcontext),
-- 
2.40.0