I had it working but i screwed up something and now i get
me@mymachine:~$ LD_PRELOAD=/home/me/libf1.o ldd FCaller
ERROR: ld.so: object '/home/me/libf1.o' from LD_PRELOAD cannot be preloaded: ignored.
ERROR: ld.so: object '/home/me/libf1.o' from LD_PRELOAD cannot be preloaded: ignored.
ERROR: ld.so: object '/home/me/libf1.o' from LD_PRELOAD cannot be preloaded: ignored.
linux-gate.so.1 => (0xb7735000)
libc.so.6 => /lib/i386-linux-gnu/libc.so.6 (0xb7579000)
/lib/ld-linux.so.2 (0xb7736000)