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#Initializing semaphor to 1 code#
C: how stack array with variable size works and result is correct? What happened in memory?.How to separate format specifiers from characters with printf.Also, there is no need to explicitly cast the return value of the shmat call to sem_t * because conversion of void * to another object type does not need an explicit cast. Those number 5s ought to be replaced with the macro NUM_PROCESSES for consistency. It is assigning a pointer to the shared memory segment to the first element of the array, but is using other elements of the array without initializing them. It is allocating the correct amount of memory, but is treating the memory as an array The code in the OP’s first attempt is incorrect. In the calls to fork(), the child process inherits the attached shared memory segment of the parent, so all the child processes will use the same semaphores in that memory segment. So the array of sem_t should be initialized within a shared memory segment (as in OP’s first attempt). An array of sem_t on the stack (as in OP’s second attempt) is not suitable for inter-process communication because the current state of the semaphores would be copied to the child processes by fork() and the child processes would operate on their own copies of the semaphores.
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