There is only 1 known compile issue with this code, and it hasn't to do with actual code, but GCC compiler itself. Not sure which all versions are affected but with -Warray-bounds on with version 4.7* it will spit out a fake warning.

#!c

gcc -c -Ofast -g -pthread -Wall kav_wiz.c -o o/kav_wiz.o
kav_wiz.c: In function ‘do_quest’:
kav_wiz.c:3080:35: warning: array subscript is above array bounds [-Warray-bounds]

GCC has fixed this issue in later version, either 4.8 or 4.9 definitely. can find the bug report here. Bug #59124