linux-kernel - [PATCH v2 10/24] ioctl_ns.2: Cast to 'unsigned long' rather than 'long' when printing with "%lx"

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Message-ID: <816259de-c577-55c7-9894-11c088720ea7@gmail.com>
Date:   Fri, 11 Sep 2020 11:13:19 +0200
From:   Alejandro Colomar <colomar.6.4.3@...il.com>
To:     "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
Cc:     linux-man@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 10/24] ioctl_ns.2: Cast to 'unsigned long' rather than
 'long' when printing with "%lx"

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'.

Cheers,

Alex

-------------------------------------------------------------
 From c5f644e798ffc5dec0c73f324a26059568865c68 Mon Sep 17 00:00:00 2001
From: Alejandro Colomar <colomar.6.4.3@...il.com>
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 <colomar.6.4.3@...il.com>
---
  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);
-- 
2.28.0