|
|
On 10 Jul., 08:51, thomas.mer...@xxxxxx wrote:
> On 10 Jul., 00:17, thomas.mer...@xxxxxx wrote:
>
>
>
> > Hello
>
> > I have problems when I try to catch a division by zero for
> > two times. I try to emulate exceptions with setjmp/longjmp.
>
> > To catch a division by zero I use a handler for the signal
> > SIGFPE. In the signal handler I use longjmp to jump to the
> > exception handler.
>
> > What happens is: The first division by zero is handled
> > correctly but the second one terminates the program.
> > To demonstrate this, use the following test program:
> > --------------------------------------------------
> > #include "stdio.h"
> > #include "setjmp.h"
>
> > #define SIGFPE 8
> > #define SIG_IGN 1
>
> > jmp_buf catch_pos;
>
> > static void handle_fpe_signal (int sig_num)
> > {
> > signal(SIGFPE, handle_fpe_signal);
> > printf("in handle_fpe_signal catch_pos=%lx\n", catch_pos);
> > longjmp(catch_pos, 1);
> > }
>
> > int main()
> > {
> > int fail_value;
> > int x;
>
> > signal(SIGFPE, handle_fpe_signal);
> > if ((fail_value = setjmp(catch_pos)) == 0) {
> > printf("before division A catch_pos=%lx\n", catch_pos);
> > x = 42/0;
> > printf("after division A\n");
> > } else {
> > printf("handler A\n");
> > }
> > printf("---------- A\n");
>
> > if ((fail_value = setjmp(catch_pos)) == 0) {
> > printf("before division B catch_pos=%lx\n", catch_pos);
> > x = 42/0;
> > printf("after division B\n");
> > } else {
> > printf("handler B\n");
> > }
> > printf("---------- B\n");
>
> > return 0; /* Never reached */
> > }
> > ---------------------------------------------------
> > Compiling and execution this test program (tst3.c) gives:
>
> > tm@penguin$ cc tst3.c
> > tst3.c: In Funktion »main«:
> > tst3.c:24: Warnung: Division durch Null
> > tst3.c:33: Warnung: Division durch Null
> > tm@penguin$ ./a.out
> > before division A catch_pos=8049860
> > in handle_fpe_signal catch_pos=8049860
> > handler A
> > ---------- A
> > before division B catch_pos=8049860
> > Floating point exception
> > tm@penguin$
>
> > Has someone an idea how a program can have more than
> > one SIGFPE catched with a setjmp/longjmp exception?
>
> > Greetings Thomas Mertes
>
> > Seed7 Homepage: http://seed7.sourceforge.net
> > Seed7 - The extensible programming language: User defined statements
> > and operators, abstract data types, templates without special
> > syntax, OO with interfaces and multiple dispatch, statically typed,
> > interpreted or compiled, portable, runs under linux/unix/windows.
>
> I forgot to mention;
> $ gcc --version
> gcc (GCC) 4.2.3 (Ubuntu 4.2.3-2ubuntu7)
>
> $ uname -a
> Linux penguin 2.6.24-19-386 #1 Wed Jun 18 14:09:56 UTC 2008 i686 GNU/
> Linux
>
> Greetings Thomas Mertes
>
> Seed7 Homepage: http://seed7.sourceforge.net
> Seed7 - The extensible programming language: User defined statements
> and operators, abstract data types, templates without special
> syntax, OO with interfaces and multiple dispatch, statically typed,
> interpreted or compiled, portable, runs under linux/unix/windows.
In the meantime I found a solution:
when I use sigsetjmp(catch_pos, -1) and siglongjmp it seems to work.
Which leaves the question open why setjmp and longjmp are not
enough (since the signal() function is called before the second FPE).
Anyway, I have a solution and a new configuration variable,
because not all operating systems have sigsetjmp...
Greetings Thomas Mertes
Seed7 Homepage: http://seed7.sourceforge.net
Seed7 - The extensible programming language: User defined statements
and operators, abstract data types, templates without special
syntax, OO with interfaces and multiple dispatch, statically typed,
interpreted or compiled, portable, runs under linux/unix/windows.
|
|