[Libreoffice] Array index at -1

Hi,

I'm running cppcheck (1.45 from sourceforge since the testing package on 
Debian repository is the 1.44 version) the whole project.
And i found these points :
[./build/libreoffice-3.2.99.2/berkeleydb/unxlngi6.pro/misc/build/db-4.7.25.NC/btree/bt_compact.c:1980]: 
(error) Array index -1 is out of bounds
=>
epg = &cp->csp[-1];

[./build/libreoffice-3.2.99.2/berkeleydb/unxlngi6.pro/misc/build/db-4.7.25.NC/btree/bt_delete.c:624]: 
(error) Array index -1 is out of bounds
=>
for (epg = &cp->csp[-1]; epg >= cp->sp; epg--) {

Are these bugs false positive or just typos ? I never saw an index to -1 
but i don't know at all C++.