Bug 1945934 - Test the optimizer does not remove gMozCrashReason assignment r=gsvelto

Differential Revision: https://phabricator.services.mozilla.com/D236764

mfbt/tests/TestMozCrash.cpp

@@ -0,0 +1,59 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/Assertions.h"
+
+#include <unistd.h>
+#include <signal.h>
+#include <string.h>
+#include <sys/wait.h>
+
+void handler(int signum) { exit(gMozCrashReason == nullptr ? 1 : 0); }
+
+int main(int argc, char** argv) {
+  // libxul starts with gMozCrashReason set to nullptr.
+  if (gMozCrashReason) {
+    fprintf(stderr, "gMozCrashReason unexpectedly starts set to %s.\n",
+            gMozCrashReason);
+    return 1;
+  }
+
+  // The strategy here is simple: fork, trigger an abort from the child and
+  // observe behavior.
+
+  pid_t child = fork();
+  if (child == 0) {
+    struct sigaction sa;
+    memset(&sa, 0, sizeof(sa));
+    sa.sa_handler = handler;
+    sigemptyset(&sa.sa_mask);
+    for (int i = 1; i < 10; ++i)
+      if (sigaction(SIGSEGV, &sa, nullptr) == -1) {
+        perror(argv[0]);
+        return 1;
+      }
+    // Trigger an actual verbose crash. This calls a function within libxul to
+    // make sure it produces verbose crash.
+    mozilla::detail::InvalidArrayIndex_CRASH(2, 2);
+  } else {
+    // Recover exit status from child, check it's an actual crash and that
+    // gMozCrashReason is set.
+    int waitres;
+    if (wait(&waitres) >= 0) {
+      if (WIFEXITED(waitres) && WEXITSTATUS(waitres) == 0) return 0;
+      fprintf(stderr,
+              "Crash didn't happen in the expected way.\n"
+              "normal exit: %d.\n"
+              "signaled exit: %d.\n"
+              "exit status: %d.\n"
+              "signal used: %d.\n",
+              WIFEXITED(waitres), WIFSIGNALED(waitres),
+              (WIFEXITED(waitres) ? WEXITSTATUS(waitres) : -1),
+              (WIFSIGNALED(waitres) ? WTERMSIG(waitres) : -1));
+      return 1;
+    }
+  }
+}

mfbt/tests/moz.build

@@ -88,6 +88,13 @@ if CONFIG["OS_ARCH"] == "WINNT":
         ]
     )
 
+if CONFIG["OS_ARCH"] == "Linux":
+    CppUnitTests(
+        [
+            "TestMozCrash",
+        ]
+    )
+
 # Not to be unified with the rest, because this test
 # sets MOZ_PRETEND_NO_JSRUST, which changes the behavior
 # of the included headers.

testing/cppunittest.toml

@@ -104,6 +104,9 @@ run-if = ["os == 'win'"]
 ["TestMemoryPressureWatcherLinux"]
 run-if = ["os == 'linux'"]
 
+["TestMozCrash"]
+skip-if = ["os != 'linux'", "asan"]
+
 ["TestMozJemallocUtils"]
 
 ["TestNativeNt"]