Get signal name from signal number

Question

I am trying to get a signal name to print when getting a signal number. I actually have :

char* getsig(int sig){
 switch (sig)
 {
 case SIGKILL:
 return "SIGKILL";
 case SIGSTOP:
 return "SIGSTOP";
 case SIGTERM:
 return "SIGTERM";
 case SIGTRAP:
 return "SIGTRAP";
 case SIGABRT:
 return "SIGABRT";
 case SIGALRM:
 return "SIGALARM";
 case SIGSEGV:
 return "SIGSEGV";
 case SIGQUIT:
 return "SIGQUIT";
 case SIGINT:
 return "SIGINT";
 case SIGCHLD:
 return "SIGCHLD";
 case SIGCONT:
 return "SIGCONT";
 case SIGPIPE:
 return "SIGPIPE";
 case SIGFPE:
 return "SIGFPE";
 case SIGILL:
 return "SIGILL";
 case 0:
 return "[NO SIGNAL TO DELIVER]";
 default:
 return "UNKN";
 }
}

I can see that this is wrong : I have no certitude that those char* names will be stored in data section on every compiler. I am certain that there is a clean way of doing such a thing, but I cannot find it on the internet. Do anyone has an idea of how I could do this task the beautiful way?

Edit

The final aim is to print a potential signal delivered by a ptrace(PTRACE_CONT, ...); call, e.g: printf("ptrace(PTRACE_CONT); [delivered %s]\n", getsig(data));

• NoShady420: stackoverflow.com/a/55511300/10281456

Answer 1

The way to do this in C is to define an array, and use designated array initializers to ensure the correct mapping between number and string, like so:

static const char *signames[] = {
 [SIGKILL] = "SIGKILL",
 [SIGSTOP] = "SIGSTOP",
 ...
 [0] = "[NO SIGNAL TO DELIVER]",
};
const char *getsig(int sig) {
 if (sig < 0 || sig >= sizeof(signames) / sizeof(*signames) || !signames[sig])
 return "UNKN";
 return signames[sig];
}

Note that it is hard to make this portable; the list of available signals varies by operating system, and some don't even have the concept of signals. Some operating systems and/or standard libraries might already have some function to convert signal numbers to strings, if you target a specific platform and don't care about compatibility, you might consider using that.

Note that strsignal() should be available on any POSIX platform, although it gives you a more human readable string like "Killed" instead of "SIGKILL".