CODEWITHSUNDEEP
c++memorysegmentation-fault
wonton
wonton

Reputation: 8307

How do I handle out of stack space segmentation fault?

Let's say I compiled using gcc --stack,4194304

Next in my program I do something like char what_is_wrong_with_me[8000000];

This will result in a segmentation fault, but the weird thing is I have a working segv_handler, where if I do something stupid like char *stupid=0; *stupid='x'; it will print an error message.

My question is, how do I handle the out of stack space segfault as well?

Upvotes: 2

Views: 600

Answers (2)

Craig Estey
Craig Estey

Reputation: 33631

You can handle this but you've exhausted your primary stack. You need to set an alternate stack for your signal handler. You can do this with a sigaltstack syscall

When installing your segfault handler with sigaction, you'll also need the SA_ONSTACK option

Upvotes: 2

Sam Varshavchik
Sam Varshavchik

Reputation: 118435

So, your process exhausted its allocated stack space (intentionally, in your case, but it doesn't matter whether it's intentional or not). As soon as an attempt is made to write the next stack frame into the unallocated page occurs, a SIGSEGV signal gets sent to the process.

An attempt is then made to invoke your installed signal handler. Now, lets remember that SIGSEGV is just like any other signal. And, as you know, when a signal handler gets invoked upon receipt of a signal, when the signal handler returns the process continues to execute.

In other words, the signal handler gets invoked as if it were a function call, and when the function call returns, the original execution thread resumes running.

Of course, you know what needs to happen for a function call, right? A new call frame gets pushed on the stack, containing the return address, and a few other things. You know, so when the function call returns, the original execution thread resumes running where it left off (in case of a signal you also get an entire register dump in there, and the rest of the CPU state, but that's an irrelevant detail).

And now, perhaps, you can figure out, all by yourself, the answer to your own question, why your signal handler does not get invoked in this situation, when the stack space has been exhausted...

Upvotes: 1

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