Re: [PATCH v2] redir: savefd: use F_DUPFD_CLOEXEC instead of F_DUPFD+F_SETFD, if available

[Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>]

наб <nabijaczleweli@xxxxxxxxxxxxxxxxxx> wrote:
> [-- text/plain, encoding quoted-printable, charset: us-ascii, 64 lines --]
> 
> This saves a syscall on every source file open, &c.;
> F_DUPFD_CLOEXEC is a mandatory part of POSIX since Issue 7
> (Austin Group Interpretation 1003.1-2001 #171).
> ---
> autoconf bits adapted almost-verbatim from the st_mtim check above
> 
> configure.ac | 13 +++++++++++++
> src/redir.c  |  7 +++++++
> 2 files changed, 20 insertions(+)
> 
> diff --git a/configure.ac b/configure.ac
> index 52aa429..b870a59 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -177,6 +177,19 @@ if test "$have_st_mtim" = "yes"; then
>                [Define if your `struct stat' has `st_mtim'])
> fi
> 
> +dnl F_DUPFD_CLOEXEC is a mandatory part of POSIX since Issue 7
> +AC_MSG_CHECKING(for F_DUPFD_CLOEXEC)
> +AC_COMPILE_IFELSE(
> +[AC_LANG_PROGRAM([#include <unistd.h>
> +#include <fcntl.h>],
> +[return fcntl(0, F_DUPFD_CLOEXEC, 0)])],
> +have_dupfd_cloexec=yes, have_dupfd_cloexec=no)
> +AC_MSG_RESULT($have_dupfd_cloexec)
> +if test "$have_dupfd_cloexec" = "yes"; then
> +       AC_DEFINE([HAVE_F_DUPFD_CLOEXEC], [1],
> +               [Define if your system supports F_DUPFD_CLOEXEC])
> +fi

Could you please define this symbol always? That is,

...
have_dupfd_cloexec=1, have_dupfd_cloexec=0)
AC_DEFINE([HAVE_F_DUPFD_CLOEXEC], [${have_dupfd_cloexec}],
	  [Set to 1 if your system supports F_DUPFD_CLOEXEC])

>        err = newfd < 0 ? errno : 0;
>        if (err != EBADF) {
>                close(ofd);
>                if (err)
>                        sh_error("%d: %s", from, strerror(err));
> +#if !HAVE_F_DUPFD_CLOEXEC
>                else
>                        fcntl(newfd, F_SETFD, FD_CLOEXEC);
> +#endif

Then we could change this to

		else if (!HAVE_F_DUPFD_CLOEXEC)
			fcntl(newfd, F_SETFD, FD_CLOEXEC);

Thanks,
-- 
Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt