Re: [Valgrind-users] Illegal instruction error in some versions of valgrind

[Steve E. <st...@ed...>]

On 27/01/26 8:17 pm, Paul Floyd via Valgrind-users wrote:
>
> On 27/01/2026 01:06, Steve Edmonds wrote:
>> Hi. I have just joined the group to see if I can resolve a long 
>> standing issue with valgrind on Opensuse.
>> I have been using some accounting software for many years, initially 
>> it ran fine and then at some point it started causing a segmentation 
>> fault.
>>
>> I then started using it with valgrind, successful with some versions 
>> of valgrind and not with others, when it fails I get the following 
>> before termination and core dump.
>>
>> ==199084==  Illegal opcode at address 0x453BC82
>> ==199084==    at 0x453BC82: write_vec (xcb_conn.c:262)
>>
>> Using valgrind from the latest Leap 15.6 and 16.0 repositories fails 
>> (valgrind-3.26.0-355.d_t.2.x86_64.rpm, 3.24.0-150600.3.3.1, 
>> 3.22.0-150600.1.3, 3.24.0-160000.2.2 and 3.25.1-160000.1.1) I do have 
>> the software running successfully with versions 3.25.1-350.d_t.1 (on 
>> Leap 15.6) and 3.13.0-lp150.4.61-x86_64 (on Leap 15.0 in a VM). I am 
>> trying to get to grips with what might determine a successful version 
>> of valgrind, I can no longer locate the rpm for 3.25.1-350.d_t.1 to 
>> try on Leap 16.0 and quite happy to build from source if there is 
>> some configuration in the source that will resolve this issue.
>
> Hi Steve
>
> Trying older Valgrind versions is unlikely solve the problem.
>
> What application are you trying to run under Valgrind? I just tried 
> Valgrind 3.25.1 on openSUSE LEAP 16.0 running kwrite and there were no 
> major issues.
>
> In gdb (with kwrite again) that piece of code looks like
>
> 261     n = *count;
> 262     if (n > IOV_MAX)
> 263 n = IOV_MAX;
>
> Nothing unusual in the assembler, like like it is using SSE instructions.
>
> Can you also post the op-code bytes that Valgrind fails to handle?
>
> Lastly, have you built your own copy of libxcb.so.1? If so, did you 
> use any GCC options like -march? There are a few amd64 CPU features 
> that like AVX512 that Valgrind does not support.
>
> Regards
>
> Paul
Thanks for replying Paul. I am going to have to shelve this for a few 
days as I have had a few setbacks with the DUP to Leap 16.0 and need to 
get a bit of work done.
A few things to sort out also with my legacy software as the update 
cleaned out a few files relating to sysV init used in 15.6.

Regards, Steve