It's not going to rewind your code back to the beginning of that line when the interrupt returns. It'll jump back into where the segfault happened, deep inside libc, which already has a copy of the variable that won't change when you change j. So, that's not going to work.
There's also a problem with calling library calls inside a signal handler. What if, for instance, a SIGSEGV happened right inside malloc(), causing a second malloc() to be called before the first one has finished? The heap may not even be in a valid state at that moment, or may be left in an invalid state when the second one returns. Nothing but system calls are signal-safe unless specifically written to avoid signal interference, and even then, not all system calls.
I also forsee another problem with this design of yours. The signal has no way to know what size buffer is needed. Why not just do this instead?
Code:
int main(void)
{
j=strdup("hello\n");
}
This creates a correct-sized buffer containing "hello\n" for you. You can free it with free() later.
HI,
I need to handle SIGUSR2 signal in my application to change the state of the application dynamically. I have implemented the signal handler. However the application is able to catch only one SIGUSR2 signal. The second SIGUSR2 signal causes the application to crash. This is happning only with... (3 Replies)
Hi folks
I'm trying to write a signal handler (in c on HPUX) that will catch the child process launched by execl when it's finished so that I can check a compliance file.
The signal handler appears to catch the child process terminating however when the signal handler completes the parent... (3 Replies)
Dear all,
I used debugger from C++ and these are the message I got:
Program received signal SIGSEGV, Segmentation fault.
0x00323fc0 in free () from /lib/tls/libc.so.6
(gdb) info s
#0 0x00323fc0 in free () from /lib/tls/libc.so.6
#1 0x00794fa1 in operator delete () from... (5 Replies)
Guys,
I'm doing signal handling in Perl. I'm trying to catch ^C signal inside the script.
There two scripts : one shell script and one perl script.
The shell script calls the perl script.
For e.g. shell script a.sh and perl scipt sig.pl.
Shell script a.sh looks something like this :... (6 Replies)
Hello all,
I am starting to learn signal handling in Linux and have been trying out some simple codes to deal with SIGALRM. The code shown below sets a timer to count down. When the timer is finished a SIGALRM is produced. The handler for the signal just increments a variable called count. This... (7 Replies)
Hi,
I have a main loop which calls a sub loop, which finally returns to the main loop itself. The main loop runs when a flag is set. Now, I have a signal handler for SIGINT, which resets the flag and thus stops the main loop. Suppose I send SIGINT while the program is in subloop, I get an error... (1 Reply)
I am trying to write a small program where I can send signals and then ask for an action to be triggered if that signal is received. For example, here is an example where I am trying to write a programme that will say you pressed ctrl*c when someone presses ctrl+c. My questions are what you would... (1 Reply)
hi friends i have a problem in signal handling ...
let me explain my problem clearly..
i have four process ..
main process forks two child process and each child process again forks another new process respectively...
the problem is whenever i kill the child process it is reforking and the... (2 Replies)
Hello,
One of our customer is getting segmentation fault when he runs his shell script which invokes our executable on AIX 6.1.
On AIX 5.3, there were no issues.
Here is the truss output.
811242: __loadx(0x0A040000, 0xF0D3A26C, 0x00000000, 0x00000009, 0x00000000) = 0xF026E884... (0 Replies)
Discussion started by: erra_krishna
0 Replies
LEARN ABOUT SUNOS
stack_violation
stack_violation(3C) Standard C Library Functions stack_violation(3C)NAME
stack_violation - determine stack boundary violation event
SYNOPSIS
#include <ucontext.h>
int stack_violation(int sig, const siginfo_t *sip, const ucontext_t *ucp);
DESCRIPTION
The stack_violation() function returns a boolean value indicating whether the signal, sig, and accompanying signal information, sip, and
saved context, ucp, represent a stack boundary violation event or a stack overflow.
RETURN VALUES
The stack_violation() function returns 0 if the signal does not represent a stack boundary violation event and 1 if the signal does repre-
sent a stack boundary violation event.
ERRORS
No errors are defined.
EXAMPLES
Example 1: Set up a signal handler to run on an alternate stack.
The following example sets up a signal handler for SIGSEGV to run on an alternate signal stack. For each signal it handles, the handler
emits a message to indicate if the signal was produced due to a stack boundary violation.
#include <stdlib.h>
#include <unistd.h>
#include <ucontext.h>
#include <signal.h>
static void
handler(int sig, siginfo_t *sip, void *p)
{
ucontext_t *ucp = p;
const char *str;
if (stack_violation(sig, sip, ucp))
str = "stack violation.
";
else
str = "no stack violation.
";
(void) write(STDERR_FILENO, str, strlen(str));
exit(1);
}
int
main(int argc, char **argv)
{
struct sigaction sa;
stack_t altstack;
altstack.ss_size = SIGSTKSZ;
altstack.ss_sp = malloc(SIGSTKSZ);
altstack.ss_flags = 0;
(void) sigaltstack(&altstack, NULL);
sa.sa_sigaction = handler;
(void) sigfillset(&sa.sa_mask);
sa.sa_flags = SA_ONSTACK | SA_SIGINFO;
(void) sigaction(SIGSEGV, &sa, NULL);
/*
* The application is now set up to use stack_violation(3C).
*/
return(0);
}
USAGE
An application typically uses stack_violation() in a signal handler that has been installed for SIGSEGV using sigaction(2) with the SA_SIG-
INFO flag set and is configured to run on an alternate signal stack.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|Interface Stability |Evolving |
+-----------------------------+-----------------------------+
|MT-Level |Async-Signal-Safe |
+-----------------------------+-----------------------------+
SEE ALSO sigaction(2), sigaltstack(2), stack_getbounds(3C), stack_inbounds(3C), stack_setbounds(3C), attributes(5)SunOS 5.10 18 Jul 2002 stack_violation(3C)
07-10-2009
