* Segfaults in SIGINT signal handler
@ 2023-10-15 13:18 Stanislav Maslovski
2023-10-15 18:14 ` Harald Anlauf
0 siblings, 1 reply; 2+ messages in thread
From: Stanislav Maslovski @ 2023-10-15 13:18 UTC (permalink / raw)
To: GFortran mailing list
Hi,
First of all, many thanks to everyone involved in developing and
maintaining gfortran!
I have been trying to use gfortran's function signal() to add a SIGINT
signal handler to my program. Gfortran's documentation for this function
says that, when the signal handler is called, it is given an argument of
integer type. However, when I try to access this argument in the
signal handler, my program segfaults.
Here are two examples:
================= this code segfaults ===================
program test_signal
implicit none
integer, parameter :: SIGINT = 2, SIG_ERR = -1
logical :: sig_received = .false.
common /signal/ sig_received
external sig_handler
if (signal(SIGINT, sig_handler) /= SIG_ERR) then
print *, "Signal handler installed"
else
print *, "Error in signal()"
endif
do while (.true.)
print *, "Waiting for signal..."
do while (.not. sig_received)
continue
enddo
print *, "Signal received!"
sig_received = .false.
enddo
end program
subroutine sig_handler(s)
implicit none
integer, parameter :: SIGINT = 2
integer, intent(in) :: s
logical sig_received
common /signal/ sig_received
if (s == SIGINT) sig_received = .true.
end subroutine
=========================================================
$ gfortran test_signal.f90
$ ./a.out
Signal handler installed
Waiting for signal...
^C
Program received signal SIGSEGV: Segmentation fault - invalid memory
reference.
Backtrace for this error:
#0 0x7f9c312218c2 in ???
#1 0x7f9c31220a55 in ???
#2 0x7f9c3105afcf in ???
at ./signal/../sysdeps/unix/sysv/linux/x86_64/libc_sigaction.c:0
#3 0x562929f153bc in ???
#4 0x7f9c3105afcf in ???
at ./signal/../sysdeps/unix/sysv/linux/x86_64/libc_sigaction.c:0
#5 0x562929f152f4 in ???
#6 0x562929f153a8 in ???
#7 0x7f9c310461c9 in __libc_start_call_main
at ../sysdeps/nptl/libc_start_call_main.h:58
#8 0x7f9c31046284 in __libc_start_main_impl
at ../csu/libc-start.c:360
#9 0x562929f150c0 in ???
#10 0xffffffffffffffff in ???
zsh: segmentation fault ./a.out
============= this code does not segfault ===============
program test_signal
implicit none
integer, parameter :: SIGINT = 2, SIG_ERR = -1
logical :: sig_received = .false.
common /signal/ sig_received
external sig_handler
if (signal(SIGINT, sig_handler) /= SIG_ERR) then
print *, "Signal handler installed"
else
print *, "Error in signal()"
endif
do while (.true.)
print *, "Waiting for signal..."
do while (.not. sig_received)
continue
enddo
print *, "Signal received!"
sig_received = .false.
enddo
end program
subroutine sig_handler(s)
implicit none
integer, intent(in) :: s
logical sig_received
common /signal/ sig_received
sig_received = .true.
end subroutine
=========================================================
What am I doing wrong?
With best regards,
--
Stanislav Maslovski
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: Segfaults in SIGINT signal handler
2023-10-15 13:18 Segfaults in SIGINT signal handler Stanislav Maslovski
@ 2023-10-15 18:14 ` Harald Anlauf
0 siblings, 0 replies; 2+ messages in thread
From: Harald Anlauf @ 2023-10-15 18:14 UTC (permalink / raw)
To: GFortran mailing list, stanislav.maslovski
Hi Stanislav,
Am 15.10.23 um 15:18 schrieb Stanislav Maslovski:
> Hi,
>
> First of all, many thanks to everyone involved in developing and
> maintaining gfortran!
>
> I have been trying to use gfortran's function signal() to add a SIGINT
> signal handler to my program. Gfortran's documentation for this function
> says that, when the signal handler is called, it is given an argument of
> integer type. However, when I try to access this argument in the
> signal handler, my program segfaults.
>
> Here are two examples:
>
> ================= this code segfaults ===================
>
> program test_signal
> implicit none
> integer, parameter :: SIGINT = 2, SIG_ERR = -1
> logical :: sig_received = .false.
> common /signal/ sig_received
> external sig_handler
> if (signal(SIGINT, sig_handler) /= SIG_ERR) then
> print *, "Signal handler installed"
> else
> print *, "Error in signal()"
> endif
> do while (.true.)
> print *, "Waiting for signal..."
> do while (.not. sig_received)
> continue
> enddo
> print *, "Signal received!"
> sig_received = .false.
> enddo
> end program
>
> subroutine sig_handler(s)
> implicit none
> integer, parameter :: SIGINT = 2
> integer, intent(in) :: s
> logical sig_received
> common /signal/ sig_received
> if (s == SIGINT) sig_received = .true.
> end subroutine
>
> =========================================================
>
> $ gfortran test_signal.f90
> $ ./a.out
> Signal handler installed
> Waiting for signal...
> ^C
> Program received signal SIGSEGV: Segmentation fault - invalid memory
> reference.
>
> Backtrace for this error:
> #0 0x7f9c312218c2 in ???
> #1 0x7f9c31220a55 in ???
> #2 0x7f9c3105afcf in ???
> at ./signal/../sysdeps/unix/sysv/linux/x86_64/libc_sigaction.c:0
> #3 0x562929f153bc in ???
> #4 0x7f9c3105afcf in ???
> at ./signal/../sysdeps/unix/sysv/linux/x86_64/libc_sigaction.c:0
> #5 0x562929f152f4 in ???
> #6 0x562929f153a8 in ???
> #7 0x7f9c310461c9 in __libc_start_call_main
> at ../sysdeps/nptl/libc_start_call_main.h:58
> #8 0x7f9c31046284 in __libc_start_main_impl
> at ../csu/libc-start.c:360
> #9 0x562929f150c0 in ???
> #10 0xffffffffffffffff in ???
> zsh: segmentation fault ./a.out
>
> ============= this code does not segfault ===============
>
> program test_signal
> implicit none
> integer, parameter :: SIGINT = 2, SIG_ERR = -1
> logical :: sig_received = .false.
> common /signal/ sig_received
> external sig_handler
> if (signal(SIGINT, sig_handler) /= SIG_ERR) then
> print *, "Signal handler installed"
> else
> print *, "Error in signal()"
> endif
> do while (.true.)
> print *, "Waiting for signal..."
> do while (.not. sig_received)
> continue
> enddo
> print *, "Signal received!"
> sig_received = .false.
> enddo
> end program
>
> subroutine sig_handler(s)
> implicit none
> integer, intent(in) :: s
> logical sig_received
> common /signal/ sig_received
> sig_received = .true.
> end subroutine
>
> =========================================================
>
> What am I doing wrong?
the man page for signal states that the interface of the signal handler is:
void (*sighandler_t)(int);
which means that the signal number is passed by value, not by reference.
If you replace
integer, intent(in) :: s
by
integer, value :: s
you'll get the intended behavior.
> With best regards,
>
^ permalink raw reply [flat|nested] 2+ messages in thread
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2023-10-15 18:14 ` Harald Anlauf
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