How can I catch SIGSEGV (segmentation fault) and get a stack trace under JNI on Android?

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I'm moving a project to the new Android Native Development Kit (i.e. JNI) and I'd like to catch SIGSEGV, should it occur (possibly also SIGILL, SIGABRT, SIGFPE) in order to present a nice crash reporting dialog, instead of (or before) what currently happens: the immediate unceremonious death of the process and possibly some attempt by the OS to restart it. (Edit: The JVM/Dalvik VM catches the signal and logs a stack trace and other useful information; I just want to offer the user the option to email that info to me really.)

The situation is: a large body of C code which I didn't write does most of the work in this application (all the game logic) and although it's well-tested on numerous other platforms, it's entirely possible that I, in my Android port, will feed it garbage and cause a crash in native code, so I want the crash dumps (both native and Java) that currently show up in the Android log (I guess it would be stderr in a non-Android situation). I'm free to modify both C and Java code arbitrarily, although the callbacks (both going in and coming out of JNI) number about 40 and obviously, bonus points for small diffs.

I've heard of the signal chaining library in J2SE, libjsig.so, and if I could safely install a signal handler like that on Android, that would solve the catching part of my question, but I see no such library for Android/Dalvik.

4 Answers

In my limited experience (non-Android), SIGSEGV in JNI code will generally crash the JVM before control is returned to your Java code. I vaguely recall hearing about some non-Sun JVM which lets you catch SIGSEGV, but AFAICR you can't expect to be able to do so.

You can try to catch them in C (see sigaction(2)), although you can do very little after a SIGSEGV (or SIGFPE or SIGILL) handler as the ongoing behaviour of a process is officially undefined.

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