[lwip-devel] [bug #53952] ip4_addr_debug_print_val unaligned structure reference compiler warning

[Ray Ozzie]

URL:
  <http://savannah.nongnu.org/bugs/?53952>

                 Summary: ip4_addr_debug_print_val unaligned structure
reference compiler warning
                 Project: lwIP - A Lightweight TCP/IP stack
            Submitted by: rozzie
            Submitted on: Sun 20 May 2018 08:06:13 PM UTC
                Category: None
                Severity: 3 - Normal
              Item Group: Compiler Warning
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: None
            lwIP version: 2.0.3

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Details:

I've been using completely unmodified 2.0.3 without any issues for months;
thank you for your time and efforts.

In the past I've been using the GCC compilers embedded within Rowley
CrossStudio, and LwIP has compiled without any warnings.

I am now converting my project to the latest version of IAR Embedded Workbench
for ARM Version (8.22.1.15700), which has a non-GCC compiler.

LwIP again compiles cleanly except for a single file, which emits warnings
about the unaligned references while trying to decompose the components of an
IPv4 address - see below.

I started trying to decompose the macros to see if I could understand the
source of the issue [obviously the references *are* unaligned, even if safely
so], but couldn't readily determine the problem.

It may be harmless in the generated code, but assuming that you do want to
resolve this to maintain a clean compile, here's the info.  

Happy to help if you want to test a potential fix.

icmp.c 

   IAR ANSI C/C++ Compiler V8.22.1.15669/W32 for ARM
   Copyright 1999-2018 IAR Systems AB.
Cortex-M edition 8.22
C:\Users\ray\dev\notebox\nbc\rtos\lwip\src\core\ipv4\icmp.c(358) :
Warning[Pa039]: use of address of unaligned structure member
C:\Users\ray\dev\notebox\nbc\rtos\lwip\src\core\ipv4\icmp.c(358) :
Warning[Pa039]: use of address of unaligned structure member
C:\Users\ray\dev\notebox\nbc\rtos\lwip\src\core\ipv4\icmp.c(358) :
Warning[Pa039]: use of address of unaligned structure member
C:\Users\ray\dev\notebox\nbc\rtos\lwip\src\core\ipv4\icmp.c(358) :
Warning[Pa039]: use of address of unaligned structure member
C:\Users\ray\dev\notebox\nbc\rtos\lwip\src\core\ipv4\icmp.c(360) :
Warning[Pa039]: use of address of unaligned structure member
C:\Users\ray\dev\notebox\nbc\rtos\lwip\src\core\ipv4\icmp.c(360) :
Warning[Pa039]: use of address of unaligned structure member
C:\Users\ray\dev\notebox\nbc\rtos\lwip\src\core\ipv4\icmp.c(360) :
Warning[Pa039]: use of address of unaligned structure member
C:\Users\ray\dev\notebox\nbc\rtos\lwip\src\core\ipv4\icmp.c(360) :
Warning[Pa039]: use of address of unaligned structure member
 
 408 bytes of CODE memory

Errors: none
Warnings: 8




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