compiling with #define in multiple files

[MA WiSo]

I have a project with multiple .h and .cpp files.
I want to compile this project and add #defines using GCC.

some of the .h files are paired with .cpp files.
some are just standalone.

each .h file has its own #define that needs to be set

how to do this ??

[writetonsharma]

I am not able to understand the problem. could you elaborate ?
What exactly a #define will do ?

[MA WiSo]

in my files i have multiple sections like this

#ifdef FOO
//some codes
#endif

i want to be able to define or undefine this FOO in compilation
each .h file has a different FOO.

now when i compile i use for example:
g++ file1.cpp file2.cpp file3.cpp -o file.o

how do i change this to alter #defines in .h files ??

[writetonsharma]

g++ -DFOO file1.cpp file2.cpp file3.cpp -o file.o

this is going to define FOO for you.

[MA WiSo]

this will define FOO in all .cpp files

but i need to define different FOO in each .h file
something like this

g++ -DFOO1 file1.h -DFOO2 file2.h -DFOO3 file3.h file1.cpp file2.cpp file3.cpp -o file.o

is that possible ??

[writetonsharma]

Yes, you can have as many defines as you want.

so,

file1.cpp
#ifdef FOO1

file2.cpp
#ifdef FOO2

and so on.