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 HPUX
sighold
sigset(3C)sigset(3C)NAME
sigset(), sighold(), sigrelse(), sigignore() - signal management
SYNOPSIS DESCRIPTION
The system defines a set of signals that can be delivered to a process. The set of signals is defined in signal(5), along with the meaning
and side effects of each signal. An alternate mechanism for handling these signals is defined here. The facilities described here should
not be used in conjunction with the other facilities described under signal(2) and sigspace(2).
allows the calling process to choose one of four ways to handle the receipt of a specific signal. sig specifies the signal and func speci-
fies the action handler.
sig can be any one of the signals described under signal(5) except or
func is assigned one of four values: or a function address. The actions prescribed by and are described under signal(5). The action pre-
scribed by and function address are described below:
Hold signal.
The signal sig is held upon receipt. Any pending signal of this signal type remains held. Only one signal of each type
is held.
Note: the signals and cannot be held.
function address Catch signal.
func must be a pointer to a function, the signal-catching handler, that is called when signal sig occurs. specifies that
the process calls this function upon receipt of signal sig. Any pending signal of this type is released. This handler
address is retained across calls to the other signal management functions listed here. Upon receipt of signal sig, the
receiving process executes the signal-catching function pointed to by func as described under signal(5) with the follow-
ing differences:
Before calling the signal-catching handler, the defined action of sig is set to During a normal return from the signal-
catching handler, the defined action is restored to func and any held signal of this type is released. If a non-local
goto (longjmp(3C)) is taken, must be called to restore the defined action to func and release any held signal of this
type.
holds the signal sig. restores the defined action of sig to that specified previously by and are used to establish critical regions of
code. is analogous to raising the priority level and deferring or holding a signal until the priority is lowered by
sets the action for signal sig to (see signal(5)).
RETURN VALUE
Upon successful completion, returns the previous value of the defined action for the specified signal sig. Otherwise, a value of is
returned and is set to indicate the error. is defined in
For the other functions, a 0 value indicates that the call succeeded. A -1 return value indicates an error occurred and is set to indicate
the reason.
ERRORS
fails and the defined action for sig is not changed if any of the following occur:
The func argument points to memory that is not a valid part of the process address space. Reliable detection of this
error is implementation dependent.
and and fail and the defined action for sig is not changed if any of the following occur:
sig is not a valid signal number.
An attempt is made to ignore, hold, or supply a handler
for a signal that cannot be ignored, held, or caught; see signal(5).
WARNINGS
These signal facilities should not be used in conjunction with signal(2) and sigspace(2).
SEE ALSO kill(1), kill(2), pause(2), signal(2), sigspace(2), wait(2), abort(3C), setjmp(3C), sigpause(3C), signal(5).
STANDARDS CONFORMANCE sigset(3C)
07-10-2009
