How to define pthread and mutex lock in C files that depend on each other?

Question

I’m new to pthread and mutex lock. I used them before but in a single file (main.c that creates the threads and locks are in the same file as functions and memory that use the locks). How to define mutex lock in C files that depend on each other? Ideally, I wish not to change the current structure.

main.c   // create threads, include `file1.h`
file1.h  
file1.c  // include `file1.h` and `lib.h`, extern a memory defined in `lib.c`
lib.h  
lib.c   // include `lib.h`, contain functions that malloc and dealloc memory, which need to be accessed by many threads

I added a main.h, and defined mutex there. I’m thinking lib.c can just import main.h and use it. Will it work? — Pippi, May 07 '16 at 00:44

score 4 · Accepted Answer · edited May 07 '16 at 17:18

You need to define the mutex in one of the .c files:

pthread_mutex_t mux;

and then you need to forward-declare it in one of the .h files:

extern pthread_mutex_t mux;

The normal convention is that you put the forward declaration in the .h file corresponding to the .c file, but there's no reason you couldn't put it in a different .h file; you just have to remember which .h to include. Make sure you include the .h file where the variable is defined and everywhere that it is used.

How to define pthread and mutex lock in C files that depend on each other?

1 Answers1