Whay can't GDB or DDD find my source code?

[rich <rehartma@artsci.wustl.edu>]

I am compiling a C program like so....

gcc -o -g foo foo.c

alternatively....

gcc -o -ggdb foo foo.c

When I run gdb, I get "(no debugging symbols found)"

When I run ddd, I get "GDB cannot find the source code of your program"

I'm running everything from the same directory, and have tried gdb
./foo, etc.

Am I just confused as to what these programs should be doing? At least
they should be able to find the source code, right? Unless there are no
errors, maybe?????

Baffled, 

Rich