Throwing an exception from within a signal handler

Question

We have a library that deals with many aspects of error reporting. I have been tasked to port this library to Linux. When running though my little test suite, one of the

Answer 1

At least in Ubuntu 16.04 x86-64, throwing out of a signal handler seems to work fine. Whether this is by design (i.e. guaranteed to work, rather than working accidentally somehow), I have not researched. I compiled the program below using g++ -o sig-throw sig-throw.cpp:

#include 
#include 
#include 
#include 

extern "C" void handler(int sig, siginfo_t *info, void *xxx)
{
    throw "Foo";
}

int main(int argc, char **argv)
{
    struct sigaction sa = {0};

    sa.sa_sigaction = handler;
#if 0
    // To ensure SIGALRM doesn't remain blocked once the signal handler raises
    // an exception, either enable the following, or add enable the sigprocmask
    // logic in the exception handler below.
    sa.sa_flags = SA_NODEFER;
#endif
    sigaction(SIGALRM, &sa, NULL);

    alarm(3);

    try {
        printf("Sleeping...\n");
        sleep(10);
        printf("Awoke\n"); // syscall interrupted
    }
    catch (...) {
        printf("Exception!\n");
#if 1
        // To ensure SIGALRM doesn't remain blocked once the signal handler
        // raises an exception, either enable the following, or add enable
        // SA_NODEFER when registering the signal handler.
        sigset_t sigs_alarm;
        sigemptyset(&sigs_alarm);
        sigaddset(&sigs_alarm, SIGALRM);
        sigprocmask(SIG_UNBLOCK, &sigs_alarm, NULL);
#endif
    }

    alarm(3);

    try {
        printf("Sleeping...\n");
        sleep(10);
        printf("Awoke\n"); // syscall interrupted
    }
    catch (...) {
        printf("Exception!\n");
    }

    return 0;
}

Here's it running:

[swarren@swarren-lx1 sig-throw]$ ./sig-throw 
Sleeping...
Exception!

For reference:

[swarren@swarren-lx1 sig-throw]$ lsb_release -a
...
Description:    Ubuntu 16.04.6 LTS
...

[swarren@swarren-lx1 sig-throw]$ dpkg -l libc6
...
ii  libc6:amd64  2.23-0ubuntu11  amd64  GNU C Library: Shared libraries

[swarren@swarren-lx1 sig-throw]$ g++ --version
g++ (Ubuntu 5.4.0-6ubuntu1~16.04.11) 5.4.0 20160609