Q:

Using Addprefix function makes the string uncomparable to another string

So, I have the following code:
OBJ := $(addprefix 'obj_', $(basename $(notdir /build/common.mk)))

so now OBJ1 is "obj_common"
ifeq ($(OBJ),obj_common)
    @echo equal (**don't know how to format indent in this website..assume there is.**)
endif

the ifeq can't compare $(OBJ) to obj_common, at least it didn't echo...
(However, if I get rid of addprefix function as follow:)
OBJ := $(basename $(notdir /build/common.mk))

so now OBJ1 is "common"
ifeq ($(OBJ),common)
    @echo equal
endif

this code would echo, which means they can compare and are equal.
I need to reference the variable $(OBJ_common) (I have a big list of this kind of variable, so I can't manually input the string by hand), but now addprefix function makes this string not a string... 
Could anyone please help me resolve the issue? If my question is not clear, please let me know. Thank you very much.

A:

Well, the mistake is in the following statement:

OBJ := $(addprefix 'obj_', $(basename $(notdir /build/common.mk)))
so now OBJ1 is "obj_common"

In fact, OBJ1 becomes 'obj'_common because of quotes that you used in the first argument to addprefix.
So without the quotes it should work fine:
OBJ := $(addprefix obj_, $(basename $(notdir /build/common.mk)))

Tip
Use warning and error functions for debugging your scripts:
OBJ := ...
$(warning so now OBJ1 is [$(OBJ1)])

