Comment 2 for bug 1274466

Its not the fault of libdb, its the fault of commit 650faab01603caac04494d54cf6b10a65c00ea13

Here is the reason for the bug:
--- apt-0.7.25.3ubuntu7/ftparchive/cachedb.h
+++ apt-0.8.16~exp12ubuntu10/ftparchive/cachedb.h
...
    struct StatStore
    {
       uint32_t Flags;
       uint32_t mtime;
- uint32_t FileSize;
+ uint64_t FileSize;
       uint8_t MD5[16];
       uint8_t SHA1[20];
       uint8_t SHA256[32];
+ uint8_t SHA512[64];
    } CurStat;
...

Adding the sha512 at the end is fine as there is a flag for the hashes so even if it reads garbage it will not use the not-yet-generated sha512 hash.

But the change of FileSize made it incompatibel.