Memory Barriers at pthread using CYGWIN

[Mümin A.]

Hi,

I wrote a simple test for pthread_barrier_wait. it won't work as expected.

result should be

r1 = 1, r2 = 1

Thanks,
Mümin
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cmake_minimum_required(VERSION 3.26)

project(test)

set(CMAKE_CXX_STANDARD 14)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
set(CMAKE_CXX_EXTENSIONS OFF)


add_definitions(-D__POSIX_VISIBLE=200112 -D_POSIX_C_SOURCE=200112)

add_executable(test main.cpp)

target_link_libraries(test pthread)
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#include <stdio.h>
#include <pthread.h>

int x = 0;
int y = 0;
int r1 = 0;
int r2 = 0;

pthread_barrier_t barrier;

void* thread1(void* arg) {
    y = 1;
    pthread_barrier_wait(&barrier);  // Memory barrier
    r1 = x;
    return NULL;
}

void* thread2(void* arg) {
    x = 1;
    pthread_barrier_wait(&barrier);  // Memory barrier
    r2 = y;
    return NULL;
}

int main() {
    pthread_t t1, t2;

    pthread_barrier_init(&barrier, NULL, 2);

    pthread_create(&t1, NULL, thread1, NULL);
    pthread_create(&t2, NULL, thread2, NULL);

    pthread_join(t1, NULL);
    pthread_join(t2, NULL);

    printf("r1 = %d, r2 = %d\n", r1, r2);

    pthread_barrier_destroy(&barrier);

    return 0;
}