Hello Sami,
On Tue, 7 May 2019 at 23:17, Sami Kerola <kerolasa@xxxxxx> wrote:
>
> Example tries to clarify one should not refer to variables that are not in
> on_exit() scope. Such variables include heap in main(). In short only
I must confess I never thought about this one at length. Why are heap
variable not in scope for fcuntions registered with
on_exit()/atexit()?
Thanks,
Michael
> variables allocated from stack make is sense when calling on_exit().
> Possible referal to global variables would technically work, but at the same
> go makes function argument pointless and in such case one ought to prefer
> atexit() instead.
>
> Signed-off-by: Sami Kerola <kerolasa@xxxxxx>
> ---
> man3/on_exit.3 | 40 ++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 40 insertions(+)
>
> diff --git a/man3/on_exit.3 b/man3/on_exit.3
> index d2c2c3b17..c074cda76 100644
> --- a/man3/on_exit.3
> +++ b/man3/on_exit.3
> @@ -100,6 +100,46 @@ It no longer occurs in Solaris (SunOS 5).
> Portable application should avoid this function, and use the standard
> .BR atexit (3)
> instead.
> +.SH EXAMPLE
> +Following program uses
> +.BR on_exit (3)
> +to display data, that is allocated until processing is done.
> +Notice that variables main() in heap are not in on_exit() scope.
> +.PP
> +.EX
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <unistd.h>
> +
> +struct data {
> + int argc;
> + char *argv;
> +};
> +
> +static void run_on_exit(int exit_val, void *arg)
> +{
> + struct data *d = (struct data *)arg;
> +
> + printf("argc: %d argv: %s\n", d->argc, d->argv);
> + free(d->argv);
> + free(d);
> + _exit(exit_val);
> +}
> +
> +int main(int argc, char **argv)
> +{
> + struct data *d;
> +
> + if (1 < argc) {
> + d = malloc(sizeof(*d));
> + d->argc = argc;
> + d->argv = strdup(argv[1]);
> + on_exit(run_on_exit, d);
> + }
> + return 0;
> +}
> +.EE
> .SH SEE ALSO
> .BR _exit (2),
> .BR atexit (3),
> --
> 2.21.0
>
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
