Hi,

I have a flag variable in a file, which will take only 2 values, either 1 or 0. In my main application I read this file to get value of the flag. Now depending upon the value of flag I need to declare variables and call functions which are across many C files.

If I use #define in any function (after reading the flag) it does not get a global scope hence cannot be used with #ifdef everywhere. Even setting a global variable and using it with if-else does not allow me to decalre variables which will have a scope through out the function.

There's a limitation that I cannot use flags in Makefile.

How should I implement this?

Thanks,
Regards,
Kranti

Let me try to understand. Your main app reads a file at runtime (so after compile). Next you want to use the value to declare variables.

If that's the case: you can't do that. The reading is done at runtime (when your app is running) and the declaring of variables is done at compile time. Also #define is a precompiler statement so will be used when you 'compile' and not when you run the application.

as wim said, you can't use pre-compiler directives for this.

you could use an environment variable
probly the easiest way.

man getenv

Hello, kranti.
If your flag must affect the behaviour of your big (many files) program and you get the value of flag in runtime, then you can define the flag in each module as
and in main function as
So, after compiling if you change the value of `flag' anywhere, then each module will know about this. If you have more than one flag, it may be useful to put all flags in one header file and include it in each module.

Hope, this is useful.