apps: Add shmem-test

apps/CMakeLists.txt

@@ -45,3 +45,4 @@ luna_app(buffer-test.cpp buffer-test)
 luna_app(socket-test.cpp socket-test)
 luna_app(socket-client.cpp socket-client)
 luna_app(input.cpp input)
+luna_app(shmem-test.cpp shmem-test)

apps/shmem-test.cpp

@@ -0,0 +1,35 @@
+#include <stdio.h>
+#include <sys/mman.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+int main()
+{
+    void* address = mmap(nullptr, PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_SHARED, -1, 0);
+    if (address == MAP_FAILED)
+    {
+        perror("mmap");
+        return 1;
+    }
+
+    int* ptr = (int*)address;
+    *ptr = 16;
+
+    pid_t child = fork();
+    if (child < 0)
+    {
+        perror("fork");
+        return 1;
+    }
+    if (child == 0)
+    {
+        *ptr = 32;
+        _exit(0);
+    }
+
+    waitpid(child, NULL, 0);
+
+    printf("the value is %d\n", *ptr);
+
+    return 0;
+}