+ void *stack;
+
+ /* FIXME: current code for stack overflow protection assumes that stacks are
+ * growing downward (PTH_STACKGROWTH == -1). Protected pages need to be put
+ * after the stack when PTH_STACKGROWTH == 1. */
+
+ if (smx_context_guard_size > 0 && !MC_is_active()) {
+
+#if defined(_XBT_WIN32) || (PTH_STACKGROWTH != -1)
+ static int warned_once = 0;
+ if (!warned_once) {
+ XBT_WARN("Stack overflow protection is known to be broken on your system. Either you're on Windows or PTH_STACKGROWTH != -1 (current value is %d).",
+ PTH_STACKGROWTH);
+ warned_once = 1;
+ }
+#endif
+
+ size_t size = smx_context_stack_size + smx_context_guard_size;
+#ifdef HAVE_MC
+ /* Cannot use posix_memalign when HAVE_MC. Align stack by hand, and save the
+ * pointer returned by xbt_malloc0. */
+ char *alloc = xbt_malloc0(size + xbt_pagesize);
+ stack = alloc - ((uintptr_t)alloc & (xbt_pagesize - 1)) + xbt_pagesize;
+ *((void **)stack - 1) = alloc;
+#elif !defined(_XBT_WIN32)
+ if (posix_memalign(&stack, xbt_pagesize, size) != 0)
+ xbt_die("Failed to allocate stack.");
+#else
+ stack = _aligned_malloc(size, xbt_pagesize);
+#endif
+
+#ifndef _XBT_WIN32
+ if (mprotect(stack, smx_context_guard_size, PROT_NONE) == -1) {
+ XBT_WARN("Failed to protect stack: %s", strerror(errno));
+ /* That's not fatal, pursue anyway. */
+ }
+#endif
+ stack = (char *)stack + smx_context_guard_size;
+ } else {
+ stack = xbt_malloc0(smx_context_stack_size);
+ }