Auto include header files using cmake and macros in c?

Question

I have a C program which has lots of includes in it, There are lots of macros in use to auto generate functions for the modules and in the build process, for example

#define MODULE_DEFINE(M) void M##_init (module* module) {\
        module->name = #M;
#define MODULE_END };

MODULE_DEFINE (hello)
        printf("module name is : %s\n",module->name);
MODULE_END

Now once the modules are compiled and linked, i need to include them all inside a common header file . One method would be to manually include all of them, but i am wondering if there is some better way to go around it ? I am already passing on them as as array shown below.

module mod_list[] = {
        MOD( hello )
};

The MOD used is yet another macro. Now the relevant part is, all the modules follow the include as

#include <modules/hello.h>

as in the example shown above. Can i somehow iterate over or create a list to auto-include from the list ? I don't mind changing from array to something else because i know that an array is defined at runtime and not possible for macro to actually iterate over that. If the iteration is possible i can define a common list to make all includes and define the array thereby automating the process a little. Thanks for any help.

Edit

As pointed this is not entirely possible only with macros. Now i am using CMake as my build tool. All the modules are placed in a separate directory in the format

modules
└── hello
    ├── hello.c
    └── hello.h

So can i somehow list all folders in CMake inside modules and pass them to configure_file to make the needed imports ?

Answer 1

The C preprocessor itself is not a sufficiently capable language to do this sort of thing. What you might want to look at is code generation, where you have some kind of pre-build step that reads your file with the MOD( hello ) lines, and generates a file that lists the corresponding #include <modules/hello.h> lines. Then, include your generated file where you need it.

You can write this pre-build step in whatever language you want, reasonable choices could be: sed, awk, perl, C, Python, Ruby, etc.

Answer 2

CMake offers the command generate_file. You use it, to replace some variable with by its values. If you use ##_init (module* ${MODULE_NAME}) and have a CMake variable within the loop over the modules called MODULE_NAME, you can reach a solution.

I am not sure whether that's a good idea. Why can't you use some configure header file?