[tz] localtime crash and fix

[Alois Treindl]

Probably I should stop using unreleased github code.

Release 2023c  does not have this bug.

On 24.11.23 16:29, Alois Treindl via tz wrote:
> correction, the bug is also in RHEL 9 with gcc version 11.4.1
> 
> Just make all from fresh git clone, and run
> ./zdump -c 1880,2010 -v Europe/London Africa/Johannesburg
> 
> 
> On 24.11.23 16:19, Alois Treindl via tz wrote:
>>
>> 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
>>>  }
>>>