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([2001:a61:2479:6801:d8fe:4132:9f23:7e8f]) by smtp.gmail.com with ESMTPSA id t203sm3092439wmg.43.2020.09.11.02.18.22 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 11 Sep 2020 02:18:22 -0700 (PDT) Cc: mtk.manpages@gmail.com, linux-man@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 10/24] ioctl_ns.2: Cast to 'unsigned long' rather than 'long' when printing with "%lx" To: Alejandro Colomar References: <20200910211344.3562-1-colomar.6.4.3@gmail.com> <20200910211344.3562-11-colomar.6.4.3@gmail.com> <816259de-c577-55c7-9894-11c088720ea7@gmail.com> From: "Michael Kerrisk (man-pages)" Message-ID: <61651116-8684-1d3f-6313-d207a4c07e17@gmail.com> Date: Fri, 11 Sep 2020 11:18:21 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <816259de-c577-55c7-9894-11c088720ea7@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 9/11/20 11:13 AM, Alejandro Colomar wrote: > Hi Michael, > > On 2020-09-11 09:24, Michael Kerrisk (man-pages) wrote: >> This may be true on Linux, but is not true on other systems. >> For example, on HP-UX, according to one header file I'm >> looking at, the return value is 'long'. > >> These kinds of casts are intended to improve code portability >> across UNIX implementations, so I think they should stay >> (although, I do wonder if they would be even better as casts >> to 'unsigned long') > > Fine, then here is the patch with the casts to 'unsigned long'. Thanks. Patch applied. Cheers, Michael > ------------------------------------------------------------- > From c5f644e798ffc5dec0c73f324a26059568865c68 Mon Sep 17 00:00:00 2001 > From: Alejandro Colomar > Date: Fri, 11 Sep 2020 10:51:26 +0200 > Subject: [PATCH v2 10/24] ioctl_ns.2: Cast to 'unsigned long' rather > than 'long' > when printing with "%lx" > > From the email conversation: > > On 2020-09-11 09:24, Michael Kerrisk (man-pages) wrote: > > Hi Alex, > > > > On 9/10/20 11:13 PM, Alejandro Colomar wrote: > >> Both major(3) and minor(3) return an 'unsigned int', > >> so there is no need to use a 'long' for printing. > >> Moreover, it should have been 'unsigned long', > >> as "%lx" expects an unsigned type. > > > > This may be true on Linux, but is not true on other systems. > > For example, on HP-UX, according to one header file I'm > > looking at, the return value is 'long'. > > > > These kinds of casts are intended to improve code portability > > across UNIX implementations, so I think they should stay > > (although, I do wonder if they would be even better as casts > > to 'unsigned long') > > > > Thanks, > > > > Michael > > Signed-off-by: Alejandro Colomar > --- > man2/ioctl_ns.2 | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/man2/ioctl_ns.2 b/man2/ioctl_ns.2 > index 818dde32c..8b8789d1f 100644 > --- a/man2/ioctl_ns.2 > +++ b/man2/ioctl_ns.2 > @@ -317,7 +317,8 @@ main(int argc, char *argv[]) > } > printf("Device/Inode of owning user namespace is: " > "[%lx,%lx] / %ld\en", > - (long) major(sb.st_dev), (long) minor(sb.st_dev), > + (unsigned long) major(sb.st_dev), > + (unsigned long) minor(sb.st_dev), > (long) sb.st_ino); > > close(userns_fd); > @@ -346,7 +347,8 @@ main(int argc, char *argv[]) > exit(EXIT_FAILURE); > } > printf("Device/Inode of parent namespace is: [%lx,%lx] / %ld\en", > - (long) major(sb.st_dev), (long) minor(sb.st_dev), > + (unsigned long) major(sb.st_dev), > + (unsigned long) minor(sb.st_dev), > (long) sb.st_ino); > > close(parent_fd); > -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/