How to fix this warning

Question

1.00/5 (1 vote)

See more:

hello!!!
I want to Create a program that receives a number N as an argument and starts N threads each displaying one of a number from 1 to N synchronously (with named or anonymous semaphores of choice) to produce an ordered sequence (12 ... N) *.
here is my code

int N;
void* f0(int k, sem_t *mutex) {
	
    for(int i = 0; i < 100; i++) {
    	if(k < N-1){
    		sem_wait(&mutex[k]);
    		//printf("value[] = %d", value[k]);
    		printf("%d\n",k+1);
    		k = k + 1;
    		sem_post(&mutex[k]);
    		//printf("i =%d \n",i);
    		

    	}
    	
    	else{
    		
    		sem_wait(&mutex[N-1]);
    		printf("%d\n",k+1);
    		k = N-k-1;
    		sem_post(&mutex[k]);
    		//printf("i =%d \n",i);
    		

    	}
    }
    
    return NULL;
}
int main(int argc, char *argv[]) {
	N = atoi(argv[1]);
	int *value;
	value= malloc(sizeof(int)*N);
	sem_t *mutex;
	mutex =malloc(sizeof(sem_t)*N);
	pthread_t pid[N];
	
	for (int i =0;i<N;i++){
		if(i==0){
			value[i]=1;
		}
		else{
			value[i]=0;
		}
	}
	for(int i=0;i<N;i++){
		sem_init(&mutex[i],0,value[i]);
	}
	int m =0;
	while(m<N){
        pthread_create(&pid[m], NULL, f0(m,&mutex),0);
        m=m+1;
        printf("m = %d\n", m );
        
	}
	printf("heyG\n");
	for (int i=0;i<N;i++){
		pthread_join(pid[i],0);
	}
	for (int i=0;i<N;i++){
		sem_destroy(&mutex[i]);
	}
	return EXIT_SUCCESS;
}

What I have tried:

I get this warning and I want to fix it

copie.c: In function ‘main’:
copie.c:60:44: warning: passing argument 2 of ‘f0’ from incompatible pointer type [-Wincompatible-pointer-types]
         pthread_create(&pid[m], NULL, f0(m,&mutex),0);
                                            ^
copie.c:11:7: note: expected ‘sem_t * {aka union <anonymous> *}’ but argument is of type ‘sem_t ** {aka union <anonymous> **}’
 void* f0(int k, sem_t *mutex) {

Posted 13-Oct-18 11:54am

Member 14016042

Updated 13-Oct-18 12:07pm

Add a Solution

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Rick York · Answer 1 · 2018-10-13T12:07:00

Solution 1

Try

C++

pthread_create( &pid[m], NULL, f0, 0 );

When passing a pointer to a function the arguments are not included.

Posted 13-Oct-18 12:07pm

Rick York

Comments

Member 14016042 13-Oct-18 18:21pm

copie.c: In function ‘main’:
copie.c:61:39: warning: passing argument 3 of ‘pthread_create’ from incompatible pointer type [-Wincompatible-pointer-types]
pthread_create(&pid[m], NULL, f0,0);
^
In file included from copie.c:3:0:
/usr/include/pthread.h:233:12: note: expected ‘void * (*)(void *)’ but argument is of type ‘void * (*)(int, sem_t *) {aka void * (*)(int, union <anonymous> *)}’
extern int pthread_create (pthread_t *__restrict __newthread,
it gives me this warning

Rick York 13-Oct-18 19:04pm

Here's the prototype for the function:

int pthread_create(pthread_t *thread, const pthread_attr_t *attr, void *(*start_routine) (void *), void *arg );

I find typedefs to be helpful in these situations.

typedef void * pvoid;
typedef pvoid (* threadfunc)( pvoid );

Your function, f0, does not comply with that prototype so you have to modify it until it does. You can define a structure that contains the data items you want to pass if you want to. I have done that in the past and it works. For you, the members of that structure would be an integer and a pointer to a sem_t.

Member 14016042 13-Oct-18 19:20pm

Here is what I did
struct DataItem
{
int k;
sem_t *mutex;
};

void* f0(struct DataItem data) {

for(int i = 0; i < 100; i++) {
if(data.k < N-1){
sem_wait(&(data.mutex)[data.k]);
//sem_wait(&mutex[k]);
printf("%d\n",data.k + 1);
//k = k + 1;
//sem_post(&mutex[k+1] );
sem_post(&(data.mutex)[data.k + 1]);
//printf("i =%d \n",i);

}

else{

//sem_wait(&mutex[k]);
sem_wait(&(data.mutex)[data.k]);

printf("%d\n",data.k + 1);
//k = N-k-1;
//sem_post(&mutex[N-k-1]);
sem_post(&(data.mutex)[N - data.k - 1]);
//printf("i =%d \n",i);

}
}

return NULL;
}
and in the main function :
while(m<N){
struct DataItem data;
data.k = m;
data.mutex = &mutex;
pthread_create(&pid[m], NULL, f0(data),0);
m=m+1;
printf("m = %d\n", m );

}

Member 14016042 13-Oct-18 19:21pm

and I get this warning

copie.c:73:14: warning: assignment from incompatible pointer type [-Wincompatible-pointer-types]
data.mutex = &mutex;

Rick York 13-Oct-18 23:56pm

If mutex is declared and used as before, I would guess that should be Hide Copy Code

data.mutex = &mutex[m];

Also, I think it should be:

pthread_create( &pid[n], NULL, f0, &data[m] );

data is the argument in the thread creation function. You probably do not want to share one instance of data with all of the threads so make an array of the structures, set each one appropriately, and pass the address of that one to the thread.

DataItem * data = (DataItem *)calloc( sizeof( DataItem ), N );
while( m < N )
{
   data[m].k = m;
   data[m].mutex = &mutex[m];
   pthread_create( &pid[m], NULL, f0, &data[m] );
   ++m;
   printf("m = %d\n", m );
}