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List:       busybox
Subject:    Re: [PATCH 2/2] libbb/u_signal_names.c: don't check errno after bb_strtou
From:       Denys Vlasenko <vda.linux () googlemail ! com>
Date:       2018-10-31 10:30:27
Message-ID: CAK1hOcNx_Viezf+NXxOOTeh0JPk_aJfv1cThH9poRZczaK6aEg () mail ! gmail ! com
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Applied, thanks!
On Wed, Sep 12, 2018 at 5:39 PM Rasmus Villemoes
<rasmus.villemoes@prevas.dk> wrote:
>
> Since we're comparing the return value to a smallish integer anyway, we
> might as well use that bb_strtou() returns UINT_MAX for malformed
> input. Referencing errno is kinda bloaty on glibc. Seems to save ~34 or
> ~45 bytes (depending on RTMINMAX_USE_LIBC_DEFINITIONS).
>
> While NSIG is not in POSIX, we do already rely on it being defined,
> compile-time const and smallish, since arrays in struct globals_misc are
> defined in terms of it.
>
> Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
> ---
>  libbb/u_signal_names.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/libbb/u_signal_names.c b/libbb/u_signal_names.c
> index 5ef5c3f28..88f63192d 100644
> --- a/libbb/u_signal_names.c
> +++ b/libbb/u_signal_names.c
> @@ -151,8 +151,12 @@ int FAST_FUNC get_signum(const char *name)
>         unsigned i;
>         unsigned sigrtmin, sigrtmax;
>
> +       /* bb_strtou returns UINT_MAX on error. We should be able to
> +        * assume NSIG is not that big... Hence no need to check errno
> +        * after bb_strtou(). */
> +       BUILD_BUG_ON(NSIG >= UINT_MAX);
>         i = bb_strtou(name, NULL, 10);
> -       if (!errno && i < NSIG) /* for shells, we allow 0 too */
> +       if (i < NSIG) /* for shells, we allow 0 too */
>                 return i;
>         if (strncasecmp(name, "SIG", 3) == 0)
>                 name += 3;
> @@ -200,7 +204,7 @@ int FAST_FUNC get_signum(const char *name)
>                         return sigrtmin;
>                 if (name[5] == '+') {
>                         i = bb_strtou(name + 6, NULL, 10);
> -                       if (!errno && i <= sigrtmax - sigrtmin)
> +                       if (i <= sigrtmax - sigrtmin)
>                                 return sigrtmin + i;
>                 }
>         }
> @@ -209,7 +213,7 @@ int FAST_FUNC get_signum(const char *name)
>                         return sigrtmax;
>                 if (name[5] == '-') {
>                         i = bb_strtou(name + 6, NULL, 10);
> -                       if (!errno && i <= sigrtmax - sigrtmin)
> +                       if (i <= sigrtmax - sigrtmin)
>                                 return sigrtmax - i;
>                 }
>         }
> --
> 2.16.4
>
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