mailing list of musl libc
 help / color / mirror / code / Atom feed
From: Christian Eggers <ceggers@arri.de>
To: "musl@lists.openwall.com" <musl@lists.openwall.com>
Subject: [musl] -Wsign-conversion warning on ARM when using CMSG_NXTHDR
Date: Wed, 16 Feb 2022 11:35:41 +0100	[thread overview]
Message-ID: <13391677.RDIVbhacDa@localhost.localdomain> (raw)


[-- Attachment #1.1: Type: text/plain, Size: 3988 bytes --]

Toolchain: Yocto Linux with poky-tiny
Host platform: openSUSE 15.3 x86_64
Target platform: arm-poky-linux-musleabi (armv7, 32 bit)

When I try to compile libkcapi [1] [2] with current
Yocto/Openembedded master branch, I get the following compiler error:

| ../git/lib/kcapi-kernel-if.c: In function '_kcapi_common_send_meta':
| ../git/lib/kcapi-kernel-if.c:193:26: error: unsigned conversion from 'long int' to 'long unsigned int' changes value from '-4' to '4294967292' [-Werror=sign-conversion]
|   193 |                 header = CMSG_NXTHDR(&msg, header);
|       |                          ^~~~~~~~~~~
| ../git/lib/kcapi-kernel-if.c:193:26: error: unsigned conversion from 'long int' to 'long unsigned int' changes value from '-4' to '4294967292' [-Werror=sign-conversion]
| ../git/lib/kcapi-kernel-if.c:213:26: error: unsigned conversion from 'long int' to 'long unsigned int' changes value from '-4' to '4294967292' [-Werror=sign-conversion]
|   213 |                 header = CMSG_NXTHDR(&msg, header);
|       |                          ^~~~~~~~~~~
| ../git/lib/kcapi-kernel-if.c:213:26: error: unsigned conversion from 'long int' to 'long unsigned int' changes value from '-4' to '4294967292' [-Werror=sign-conversion]

Note: libcapi uses the '-Werror' and  '-Wconversion' flags.

For testing, I created a minimal code snipset (cmsg.c):

#include <stddef.h>
#include <sys/socket.h>

void foo(void)
{
        struct msghdr msg = {0};
        struct cmsghdr *header = NULL;

        header = CMSG_FIRSTHDR(&msg);
        header = CMSG_NXTHDR(&msg, header);
}

# arm-poky-linux-musleabi-gcc   --sysroot=<...> -Werror -Wconversion   -c -o cmsg.o cmsg.c
cmsg.c: In function 'foo':
cmsg.c:10:18: error: unsigned conversion from 'long int' to 'long unsigned int' changes value from '-4' to '4294967292' [-Werror=sign-conversion]
   10 |         header = CMSG_NXTHDR(&msg, header);
      |                  ^~~~~~~~~~~
cmsg.c:10:18: error: unsigned conversion from 'long int' to 'long unsigned int' changes value from '-4' to '4294967292' [-Werror=sign-conversion]


When replace CMSG_NXTHDR() by the expanded macro code, I get the following errors:

cmsg.c: In function 'foo':
cmsg.c:12:46: error: unsigned conversion from 'long int' to 'long unsigned int' changes value from '-4' to '4294967292' [-Werror=sign-conversion]
   12 |     (((header)->cmsg_len + sizeof(long) - 1) & ~(long)(sizeof(long) - 1)) + sizeof(struct cmsghdr) >= ((unsigned char *)(&msg)->msg_control + (&msg)->msg_controllen) - (unsigned char *)(header) \
      |                                              ^
cmsg.c:13:99: error: unsigned conversion from 'long int' to 'long unsigned int' changes value from '-4' to '4294967292' [-Werror=sign-conversion]
   13 |     ? 0 : (struct cmsghdr *)((unsigned char *)(header) + (((header)->cmsg_len + sizeof(long) - 1) & ~(long)(sizeof(long) - 1))));
      |                                                                                                   ^


[1] https://git.openembedded.org/meta-openembedded/tree/meta-oe/recipes-crypto/libkcapi?h=master
[2] https://github.com/smuellerDD/libkcapi/tree/2936ecd060c299157ac880650ba2c9fd94d27bb1




_______________________________________________________
Christian
Eggers
Software Engineer
​
ARRI
Arnold & Richter Cine Technik GmbH & Co. Betriebs KG
Arriweg 17,
83071
Stephanskirchen
www.arri.com

+49 8036 3009-3118
CEggers@arri.de

​
Get all the latest information from www.arri.com, Facebook, Twitter, Instagram and YouTube.

Arnold & Richter Cine Technik GmbH & Co. Betriebs KG
Sitz: München - Registergericht: Amtsgericht München - Handelsregisternummer: HRA 57918
Persönlich haftender Gesellschafter: Arnold & Richter Cine Technik GmbH
Sitz: München - Registergericht: Amtsgericht München - Handelsregisternummer: HRB 54477
Geschäftsführer: Dr. Michael Neuhäuser; Stephan Schenk; Walter Trauninger; Markus Zeiler

​

[-- Attachment #1.2: Type: text/html, Size: 13143 bytes --]

[-- Attachment #2: image092396.png --]
[-- Type: image/png, Size: 528 bytes --]

[-- Attachment #3: image623061.png --]
[-- Type: image/png, Size: 824 bytes --]

             reply	other threads:[~2022-02-16 12:42 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-02-16 10:35 Christian Eggers [this message]
2022-02-16 18:03 ` Khem Raj
2022-02-17 12:37 ` [musl] " Christian Eggers

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=13391677.RDIVbhacDa@localhost.localdomain \
    --to=ceggers@arri.de \
    --cc=musl@lists.openwall.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
Code repositories for project(s) associated with this public inbox

	https://git.vuxu.org/mirror/musl/

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).