Question

I am writing an application in C which uses both user defined satically linked library(using -l option) and dynamically linked library that i preload(using ld-preload). Now I have a variable (a socket connection) that is set up from the statically linked library and the same client socket is to be used by the other shared libraries too.

How do i declare and maintain the value this client socket across libraries till the connection is exclusively broken from the calling process.

Thanks

Answer 1

I have never done this but seems like putting:

extern int yourfileno;

into the header file for the static library should work.
Declare this global variable in one of the c files for the same library.

Really this is the same as creating get/set routines in the library.

Some might consider it better practice to have the static library declare a struct definition:

typedef struct {
        int fileno;
        int is_opened;
        ...other stuf;
} StatLibType;

Then have you main program call something like:

StatLibType *statlib_new_connection();

Pass the newly created structure to the other dynaimic library so that it can use it.