[PATCH v4] shell: exchange Dijkstra $(( )) evaluator..

[Harald van Dijk]

On 07/09/2022 13:43, Steffen Nurpmeso wrote:
> Harald van Dijk wrote in
>   <92eff87d-3bfe-b1bb-03e1-5f280184434d at gigawatt.nl>:
>    ...
>   |The supplied patch appears to fix both #1 and #2, but it has alignment
>   |issues: when UBSAN is enabled, I see a lot of "runtime error: store to
>   |misaligned address <...> for type 'char *', which requires 4 byte
>   |alignment" warnings when using shell arithmetic.
> 
> ASAN works, UBSAN i have not tried.  How can char* require 4 byte
> alignment?

This message means the char * object itself needs to be aligned on a 4 
byte boundary, and isn't. It doesn't say anything about what the char * 
points to. It's the same alignment requirement that results (on typical 
platforms) in padding in struct S { char a; char *b; } s; between the 
s.a and s.b members, despite the fact that as you rightly hint, s.b can 
hold values pointing anywhere without alignment issues.

Cheers,
Harald van Dijk