sigprocmask( ) blocking signals in UNIX

i have written a small piece of code. This code first blocks the {SIGSEGV}, then adds SIGRTMIN to the same set. So, my final signal set is, {SIGSEGV,SIGRTMIN}. Thus, if i use SIG_UNBLOCK, as per my understanding, first SIGRTMIN should be unblocked, and then again if i invoke SIG_UNBLOCK, SIGSEGV should be unblocked.

That is, 1) {SIGSEGV,SIGRTMIN} 2) SIG_UNBLOCK = unblock SIGRTMIN, 3) Again invoke SIG_UNBLOCK = unblock SIGSEGV.
I am giving the process a SIGRTMIN only, thus my second unblock should halt the process with SIGRTMIN. But it is not. Please help.
**N.B: Please don't give links to answers of other questions on sigprocmask( ), i have seen them and they don't clarify my question.**

enter code here
#include <signal.h>
#include <unistd.h>
#include <stdio.h>

int main()
{
sigset_t old_set,new_set;
sigemptyset(&old_set);
sigemptyset(&new_set);

if(sigaddset(&old_set,SIGSEGV)==0)
{
printf("sigaddset successfully added for SIGSEGV\n");
}
sigprocmask(SIG_BLOCK,&old_set,NULL); // SIGSEGV signal is masked
kill(0,SIGSEGV);


//*****************************************************************

if(sigaddset(&new_set,SIGRTMIN)==0)
{
printf("sigaddset successfully added for SIGRTMIN\n");
}
sigprocmask(SIG_BLOCK,&new_set,&old_set); // SIGRTMIN signal is masked
kill(0,SIGSEGV);

//****************** Unblock one signal at a time ******************

sigprocmask(SIG_UNBLOCK,&new_set,&old_set); // SIGRTMIN signal is unmasked
sigprocmask(SIG_UNBLOCK,&new_set,&old_set); // SIGSEGV signal is unmasked
}

Output:
[root@dhcppc0 signals]# ./a.out
sigaddset successfully added for SIGSEGV
sigaddset successfully added for SIGRTMIN
(Note:SIGSEGV is not received even after sigprocmask(SIG_UNBLOCK,&new_set,&old_set); a second time)

Your premise is wrong. The whole set gets blocked and unblocked with a single call of `sigprocmask`.

Also, normally you would create a set containing every signal you want to block, then you would attempt to block them all with `sigprocmask(SIG_BLOCK, pointer_to_sigset);`.

Your code doesn't really unblock SIGSEGV though. Here's what i would write WITHOUT error handling, because it would make the snippet unnecessarily long. Check every function
for errors though, the lists of possible errors are provided by man pages:

/* ... */
sigset_t signal_set; /* We don't need oldset in this program. You can add it,
but it's best to use different sigsets for the second
and third argument of sigprocmask. */
sigemptyset(&signal_set);

sigaddset(&signal_set, SIGSEGV);
sigaddset(&signal_set, SIGRTMIN);

/* now signal_set == {SIGSEGV, SIGRTMIN} */

sigprocmask(SIG_BLOCK, &signal_set, NULL): /* As i said, we don't bother with the
oldset argument. */

kill(0,SIGSEGV);
kill(0,SIGSEGV); /* SIGSEGV is not a realtime signal, so we can send it twice, but
it will be recieved just once */

sigprocmask(SIG_UNBLOCK, &signal_set, NULL); /* Again, don't bother with oldset */

/* SIGSEGV will be received here */

Of course, you might want to split blocking the signals into two operations on separate sets. The mechanism works like this: there is some set of blocked signals, which would replace oldset if you provided an oldset argument. You can add to that set with `SIG_BLOCK`, remove from that set with `SIG_UNBLOCK`, and change the whole set to your liking with `SIG_SETMASK` arguments of the `sigprocmask` function.

As kubi pointed out: Here is the modified code, problem is that, i messed up with old_set and new_set. The SIGSEGV was added in old_set, which was not unblocked, and hence i did not receive Segmentation fault (SIGSEGV signal).
Thanks to kubi.

enter code here
#include <signal.h>
#include <unistd.h>
#include <stdio.h>

int main()
{
sigset_t old_set,new_set;
sigemptyset(&old_set);
sigemptyset(&new_set);

if(sigaddset(&old_set,SIGSEGV)==0)
{
printf("sigaddset successfully added for SIGSEGV\n");
}
sigprocmask(SIG_BLOCK,&new_set,&old_set); // SIGSEGV signal is masked
kill(0,SIGSEGV);


//*****************************************************************

if(sigaddset(&new_set,SIGRTMIN)==0)
{
printf("sigaddset successfully added for SIGRTMIN\n");
}
if(sigprocmask(SIG_BLOCK,&new_set,&old_set)==-1) // SIGRTMIN signal is masked
{
perror("sigprocmask");
}
kill(0,SIGSEGV);


//****************** Unblock all signals ******************

if(sigprocmask(SIG_UNBLOCK,&new_set,&old_set)==-1) // SIGRTMIN signal is unmasked
{
perror("sigprocmask");
}
}