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copied!<p><strong>Edit:</strong> From Jelly Bean onwards you can't get the stack trace, because <a href="https://groups.google.com/forum/?fromgroups=#!topic/android-developers/6U4A5irWang" rel="noreferrer"><code>READ_LOGS</code> went away</a>. :-(</p> <p>I actually got a signal handler working without doing anything too exotic, and have released code using it, which you can see <a href="https://github.com/chrisboyle/sgtpuzzles/tree/9561.1" rel="noreferrer">on github</a> (edit: linking to historical release; I removed the crash handler since then). Here's how:</p> <ol> <li>Use <code>sigaction()</code> to catch the signals and store the old handlers. (<a href="http://github.com/chrisboyle/sgtpuzzles/blob/8750.5/android.c#L570" rel="noreferrer">android.c:570</a>)</li> <li>Time passes, a segfault happens.</li> <li>In the signal handler, call up to JNI one last time and then call the old handler. (<a href="http://github.com/chrisboyle/sgtpuzzles/blob/8750.5/android.c#L528" rel="noreferrer">android.c:528</a>)</li> <li>In that JNI call, log any useful debugging info, and call <a href="http://developer.android.com/reference/android/app/Activity.html#startActivity(android.content.Intent)" rel="noreferrer"><code>startActivity()</code></a> on an activity that is flagged as needing to be in its own process. (<a href="http://github.com/chrisboyle/sgtpuzzles/blob/8750.5/android/src/name/boyle/chris/sgtpuzzles/SGTPuzzles.java#L962" rel="noreferrer">SGTPuzzles.java:962</a>, <a href="http://github.com/chrisboyle/sgtpuzzles/blob/8750.5/android/AndroidManifest.xml#L28" rel="noreferrer">AndroidManifest.xml:28</a>)</li> <li>When you come back from Java and call that old handler, the Android framework will connect to <code>debuggerd</code> to log a nice native trace for you, and then the process will die. (<a href="http://android.git.kernel.org/?p=platform/bionic.git;a=blob;f=linker/debugger.c" rel="noreferrer">debugger.c</a>, <a href="http://android.git.kernel.org/?p=platform/system/core.git;a=blob;f=debuggerd/debuggerd.c" rel="noreferrer">debuggerd.c</a>)</li> <li>Meanwhile, your crash-handling activity is starting up. Really you should pass it the PID so it can wait for step 5 to complete; I don't do this. Here you apologise to the user and ask if you can send a log. If so, gather the output of <code>logcat -d -v threadtime</code> and launch an <code>ACTION_SEND</code> with recipient, subject and body filled in. The user will have to press Send. (<a href="http://github.com/chrisboyle/sgtpuzzles/blob/8750.5/android/src/name/boyle/chris/sgtpuzzles/CrashHandler.java" rel="noreferrer">CrashHandler.java</a>, <a href="http://github.com/chrisboyle/sgtpuzzles/blob/8750.5/android/src/name/boyle/chris/sgtpuzzles/SGTPuzzles.java#L462" rel="noreferrer">SGTPuzzles.java:462</a>, <a href="http://github.com/chrisboyle/sgtpuzzles/blob/8750.5/android/res/values/strings.xml#L41" rel="noreferrer">strings.xml:41</a></li> <li>Watch out for <code>logcat</code> failing or taking more than a few seconds. I have encountered one device, the T-Mobile Pulse / Huawei U8220, where logcat immediately goes into the <code>T</code> (traced) state and hangs. (<a href="http://github.com/chrisboyle/sgtpuzzles/blob/8750.5/android/src/name/boyle/chris/sgtpuzzles/CrashHandler.java#L70" rel="noreferrer">CrashHandler.java:70</a>, <a href="http://github.com/chrisboyle/sgtpuzzles/blob/8750.5/android/res/values/strings.xml#L51" rel="noreferrer">strings.xml:51</a>)</li> </ol> <p>In a non-Android situation, some of this would be different. You'd need to gather your own native trace, see <a href="https://stackoverflow.com/questions/77005/how-to-generate-a-stacktrace-when-my-gcc-c-app-crashes">this other question</a>, depending on what sort of libc you have. You'd need to handle dumping that trace, launching your separate crash-handler process, and sending the email in some appropriate ways for your platform, but I imagine the general approach should still work.</p>

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