When using libaacs with mythtv I was getting the following crash:
  Program received signal SIGSEGV, Segmentation fault.
  0xb052085a in yylex () from /usr/lib/dri/i965_dri.so
  (gdb) bt
  #0  0xb052085a in yylex () from /usr/lib/dri/i965_dri.so
  #1  0xafe1529a in yyparse (scanner=0xafd24b48, dklist=0xafd3fa60, pklist=0xae054a70, clist=0xafd39af8, celist=0xae086908, dkplist=0x0) at keydbcfg-parser.c:1537
        #2  0xafe15a22 in keydbcfg_parse_config (cfgfile=0xae036898, path=0xae0517c8 "/var/lib/mythtv/.mythtv/KEYDB.cfg") at file/keydbcfg-parser.y:440

Obviously the linker has picked the wrong yylex.

I solved this with the following patch which renames all the yy* symbols
to libaacs_yy*.