Question

(Environment: gcc/g++ 4.6.1 in -std=gnu++0x mode on Linux 3.0 / x86_64…)

#include <stdlib.h>
#include <signal.h>
#include <iostream>

using namespace std;

class SegmentationFault {};

void ThrowSegmentationFault(int)
{
    throw SegmentationFault();
}

void ohno(char* x)
{
    *x = 42;
}

int main()
{
    signal(SIGSEGV, ThrowSegmentationFault);

    try
    {
        ohno(0);
    }
    catch (const SegmentationFault&)
    {
        cout << "success" << endl;
    }
}

By compiling the above with the -fnon-call-exceptions flag, it allows the SIGSEGV signal handler to throw an exception, and when run it will print “success”. The documentation of the -fnon-call-exceptions gcc flag reads as follows:

Generate code that allows trapping instructions to throw
exceptions. Note that this requires platform-specific runtime support
that does not exist everywhere. Moreover, it only allows trapping
instructions to throw exceptions, i.e. memory references or floating
point instructions. It does not allow exceptions to be thrown from
arbitrary signal handlers such as SIGALRM.

My question is which of the signals are trapping instructions and which are not?

#define SIGHUP           1
#define SIGINT           2
#define SIGQUIT          3
#define SIGILL           4
#define SIGTRAP          5
#define SIGABRT          6
#define SIGIOT           6
#define SIGBUS           7
#define SIGFPE           8
#define SIGKILL          9
#define SIGUSR1         10
#define SIGSEGV         11
#define SIGUSR2         12
#define SIGPIPE         13
#define SIGALRM         14
#define SIGTERM         15
#define SIGSTKFLT       16
#define SIGCHLD         17
#define SIGCONT         18
#define SIGSTOP         19
#define SIGTSTP         20
#define SIGTTIN         21
#define SIGTTOU         22
#define SIGURG          23
#define SIGXCPU         24
#define SIGXFSZ         25
#define SIGVTALRM       26
#define SIGPROF         27
#define SIGWINCH        28
#define SIGIO           29
#define SIGPOLL         SIGIO
/*
#define SIGLOST         29
*/
#define SIGPWR          30
#define SIGSYS          31
#define SIGUNUSED       31

Answer 1

SIGILL, SIGTRAP, SIGBUS, SIGFPE, SIGSEGV, SIGSTKFLT are the most probable synchronous signals (i.e., generated by hardware as consequence of an instruction trying to do something invalid).