LaMont's Favorites...

"BUT IT WORKS ON MY PENTIUM..."
config.{guess,sub} out of date
sizeof(int) != sizeof(pointer)
hppa == hp-ux (or mips == irix), etc.
gcc (g++) v3 errors, particularly on i386
build dependencies on old compilers or lib versions
non-PIC in shared objects, similar policy violations
assuming that char == [un]signed char. (s390)
MU's that exclude the arch, rather than fixing it...
Zero Tolerance for Porting Problems Policy