[CMake] add_definitions & "string" values

[Welter Luigi Silva]

Hi again,
I'm trying to have a definition with a string value, say, "foo".
However, when I tried the following command:

add_definitions(-DFOO="foo")

and used FOO in my source file -- in a command like printf("%s\n", FOO) --
I got 'foo' without the quotes, which is not a valid string literal, as 
I wished it was.
I've also tried the command bellow but it did not work as well:
add_definitions(-DFOO="\"foo\"")

So, how do I define this correctly in a CMakeList.txt file?

thx,
Welter
p.s.: hope this question is not so dumb as my previous one :-)