Heap corruption in DateTime.strftime() on 32 bit for certain format strings

(originally send by e-mail on 4 Jun 2016) Setting a very high precision in the date_strftime_with_tmx() function, the following check (in the STRFTIME macro in date_strftime.c) will not work as expected if 's' >= 0x80000000 (this is the same type of issue as the other vulnerability I submitted). ```c 124 if (start + maxsize < s + precision) { \ 125 errno = ERANGE; \ 126 return 0; \ 127 } ``` This code causes a crash on my 32 bit system: ```ruby require 'date' d = DateTime.new(2007,11,19,8,37,48,"-06:00") d.strftime("%2147483647c") ``` 64 bit is probably not affected (strictly technically possible, but unlikely). Let me know if you need more information. Guido