[tz] localtime crash and fix

[Alois Treindl]

I can demonstrate the bug.
Please try

zdump -c 1880,2010 -v Europe/London Africa/Johannesburg
in gdb debugger

b tzload

it stops 3 times.
I let it run tzloadbody.

Once it loaded Johannesburg, I look at structure st

p *sp
$1 = {leapcnt = 0, timecnt = 6, typecnt = 5, charcnt = 9, goback = 
false, goahead = true,  ...

The goahead=true is incorrect.

It should be goahead=false

This happens only when I load several zones, i.e. Johannesburg after London.

None of the compile options like -std=c99 or -std=gnu11 fixes that issue 
on my RHEL 7 compiler gcc version 4.8.5.

I also tried compiler gcc version 9.3.1, same problem.

When I compile on RHEL 9 with gcc version 11.4.1 the problem does not 
appear.
it gives goahead=false

The patch memset(&ls, 0, sizeof(ls)); fixes the issue for gcc version 
4.8.5 and gcc version 9.3.1.



On 23.11.23 19:32, Alois Treindl via tz wrote:
>
> I have observed occasional crashes in localtime.c in the current 
> github version.
>
> In one of my applications, localtime() is called multiple times for 
> several zones.
>
> The condition when the segmentation fault appears are herd to 
> reproduce or demonstrate.
>
> This patch in function tzload() however solves the issue:
>
> --- localtime.c    2023-11-16 20:18:01.904577574 +0100
> +++ a/localtime.c    2023-11-23 19:22:21.062249899 +0100
> @@ -769,6 +769,7 @@
>    }
>  #else
>    union local_storage ls;
> +  memset(&ls, 0, sizeof(ls));
>    return tzloadbody(name, sp, doextend, &ls);
>  #endif
>  }
>
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