$ wish
% pack [scale .s]
% set fooie 5.79e99
5.79e99
% .s config -variable fooie
*** buffer overflow detected ***: wish terminated
======= Backtrace: =========
/lib/x86_64-linux-gnu/libc.so.6(+0x70bcb)[0x7f29259aabcb]
/lib/x86_64-linux-gnu/libc.so.6(__fortify_fail+0x37)[0x7f2925a33227]
/lib/x86_64-linux-gnu/libc.so.6(+0xf7360)[0x7f2925a31360]
/lib/x86_64-linux-gnu/libc.so.6(+0xf6919)[0x7f2925a30919]
/lib/x86_64-linux-gnu/libc.so.6(_IO_default_xsputn+0xac)[0x7f29259aebdc]
/lib/x86_64-linux-gnu/libc.so.6(+0x4be81)[0x7f2925985e81]
/lib/x86_64-linux-gnu/libc.so.6(_IO_vfprintf+0xf32)[0x7f2925981c32]
/lib/x86_64-linux-gnu/libc.so.6(__vsprintf_chk+0x8c)[0x7f2925a309ac]
....
7f2927dad000-7f2927dae000 rw-p 00024000 08:08 3014738                    /lib/x86_64-linux-gnu/ld-2.24.so
7f2927dae000-7f2927daf000 rw-p 00000000 00:00 0 
7ffc9d5d4000-7ffc9d5f5000 rw-p 00000000 00:00 0                          [stack]
7ffc9d5fa000-7ffc9d5fc000 r--p 00000000 00:00 0                          [vvar]
7ffc9d5fc000-7ffc9d5fe000 r-xp 00000000 00:00 0                          [vdso]
ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0                  [vsyscall]
Aborted
$
Haven't bothered to include whole stack trace as it is so easy to reproduce
This was on Linux, same thing happens on Mac OS but not Windows

This looks like a very valid ticket in the wrong tracker. The present tracker records issues with the core.tcl.tk *website*.
 
Please reopen the same ticket in the correct tracker:

https://core.tcl.tk/tk/

[https://core.tcl.tk/tk/tktview?name=55b95f578a]