Re: [PATCH 29/32] sigaction.2: Apply minor tweaks to Peter's patch

["Alejandro Colomar (man-pages)" <alx.manpages@gmail.com>]

On 7/28/21 10:20 PM, Alejandro Colomar wrote:
> - Move example program to a new EXAMPLES section
> - Invert logic in the handler to have the failure in the conditional path,
>    and the success in out of any conditionals.
> - Use NULL, EXIT_SUCCESS, and EXIT_FAILURE instead of magic numbers
> - Separate declarations from code
> - Put function return type on its own line
> - Put function opening brace on its line
> 
> Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>

I forgot to CC Peter here.

> ---
>   man2/sigaction.2 | 76 +++++++++++++++++++++++++++---------------------
>   1 file changed, 43 insertions(+), 33 deletions(-)
> 
> diff --git a/man2/sigaction.2 b/man2/sigaction.2
> index 4bf6f095e..18404dde1 100644
> --- a/man2/sigaction.2
> +++ b/man2/sigaction.2
> @@ -936,39 +936,6 @@ because they were introduced before Linux 5.11.
>   However, in general, programs may assume that these flags are supported,
>   since they have all been supported since Linux 2.6,
>   which was released in the year 2003.
> -.PP
> -The following example program exits with status 0 if
> -.B SA_EXPOSE_TAGBITS
> -is determined to be supported, and 1 otherwise.
> -.PP
> -.EX
> -#include <signal.h>
> -#include <stdio.h>
> -#include <unistd.h>
> -
> -void handler(int signo, siginfo_t *info, void *context) {
> -    struct sigaction oldact;
> -    if (sigaction(SIGSEGV, 0, &oldact) == 0 &&
> -        !(oldact.sa_flags & SA_UNSUPPORTED) &&
> -        (oldact.sa_flags & SA_EXPOSE_TAGBITS)) {
> -        _exit(0);
> -    } else {
> -        _exit(1);
> -    }
> -}
> -
> -int main(void) {
> -    struct sigaction act = {0};
> -    act.sa_flags = SA_SIGINFO | SA_UNSUPPORTED | SA_EXPOSE_TAGBITS;
> -    act.sa_sigaction = handler;
> -    if (sigaction(SIGSEGV, &act, 0) != 0) {
> -        perror("sigaction");
> -        return 1;
> -    }
> -
> -    raise(SIGSEGV);
> -}
> -.EE
>   .SH RETURN VALUE
>   .BR sigaction ()
>   returns 0 on success; on error, \-1 is returned, and
> @@ -1174,6 +1141,49 @@ This bug was fixed in kernel 2.6.14.
>   .SH EXAMPLES
>   See
>   .BR mprotect (2).
> +.PP
> +The following example program exits with status
> +.B EXIT_SUCCESS
> +if
> +.B SA_EXPOSE_TAGBITS
> +is determined to be supported, and
> +.B EXIT_FAILURE
> +otherwise.
> +.PP
> +.EX
> +#include <signal.h>
> +#include <stdlib.h>
> +#include <stdio.h>
> +#include <unistd.h>
> +
> +void
> +handler(int signo, siginfo_t *info, void *context)
> +{
> +    struct sigaction oldact;
> +
> +    if (sigaction(SIGSEGV, NULL, &oldact) != 0 ||
> +        (oldact.sa_flags & SA_UNSUPPORTED) ||
> +        !(oldact.sa_flags & SA_EXPOSE_TAGBITS)) {
> +        _exit(EXIT_FAILURE);
> +    }
> +    _exit(EXIT_SUCCESS);
> +}
> +
> +int
> +main(void)
> +{
> +    struct sigaction act = {0};
> +
> +    act.sa_flags = SA_SIGINFO | SA_UNSUPPORTED | SA_EXPOSE_TAGBITS;
> +    act.sa_sigaction = &handler;
> +    if (sigaction(SIGSEGV, &act, NULL) != 0) {
> +        perror("sigaction");
> +        exit(EXIT_FAILURE);
> +    }
> +
> +    raise(SIGSEGV);
> +}
> +.EE
>   .SH SEE ALSO
>   .BR kill (1),
>   .BR kill (2),
> 


-- 
Alejandro Colomar
Linux man-pages comaintainer; https://www.kernel.org/doc/man-pages/
http://www.alejandro-colomar.es/