From: Otto Moerbeek <otto.moerbeek@open-xchange.com>
Date: Wed, 18 Jan 2023 14:52:57 +0000 (+0100)
Subject: Add a test to check that we can use the specified stack size
X-Git-Tag: dnsdist-1.8.0-rc1~100^2~3
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=a0daac592818a097fc8e60f23db7009b14cc6a64;p=thirdparty%2Fpdns.git

Add a test to check that we can use the specified stack size

Actual test of the guard pages can be done, but is hard to fit in the test framework.
To test manually decrease the headroom const to 0
---

diff --git a/pdns/recursordist/test-mtasker.cc b/pdns/recursordist/test-mtasker.cc
index fb678897be..83d0930d8e 100644
--- a/pdns/recursordist/test-mtasker.cc
+++ b/pdns/recursordist/test-mtasker.cc
@@ -6,6 +6,7 @@
 #endif
 #include <boost/test/unit_test.hpp>
 #include "mtasker.hh"
+#include <fcntl.h>
 
 BOOST_AUTO_TEST_SUITE(mtasker_cc)
 
@@ -40,6 +41,43 @@ BOOST_AUTO_TEST_CASE(test_Simple)
   BOOST_CHECK_EQUAL(g_result, o);
 }
 
+static const size_t stackSize = 8 * 1024;
+static const size_t headroom = 256; // Decrease to hit stackoverflow
+
+static void doAlmostStackoverflow(void* arg)
+{
+  auto* mt = reinterpret_cast<MTasker<>*>(arg);
+  int localvar[stackSize / sizeof(int) - headroom]; // expermimentally derived headroom
+  localvar[0] = 0;
+  localvar[sizeof(localvar) / sizeof(localvar[0]) - 1] = 12;
+  if (mt->waitEvent(localvar[sizeof(localvar) / sizeof(localvar[0]) - 1], &localvar[0]) == 1) {
+    g_result = localvar[0];
+  }
+}
+
+BOOST_AUTO_TEST_CASE(test_AlmostStackOverflow)
+{
+  MTasker<> mt(stackSize);
+  mt.makeThread(doAlmostStackoverflow, &mt);
+  struct timeval now;
+  gettimeofday(&now, 0);
+  bool first = true;
+  int o = 25;
+  for (;;) {
+    while (mt.schedule(&now)) {
+      ;
+    }
+    if (first) {
+      mt.sendEvent(12, &o);
+      first = false;
+    }
+    if (mt.noProcesses()) {
+      break;
+    }
+  }
+  BOOST_CHECK_EQUAL(g_result, o);
+}
+
 #if defined(HAVE_FIBER_SANITIZER) && defined(__APPLE__) && defined(__arm64__)
 
 // This test is buggy on MacOS when compiled with asan. It also causes subsequents tests to report spurious issues.