OC checks whether the given pointer is a valid nsobject object

#import <malloc/malloc.h>#import <objc/runtime.h> static sigjmp_buf sigjmp_env; void PointerReadFailedHandler(int signum){    siglongjmp (sigjmp_env, 1);} BOOL IsPointerAnObject(const void *testPointer, BOOL *allocatedLargeEnough){    *allocatedLargeEnough = NO;         // Set up SIGSEGV and SIGBUS handlers    struct sigaction new_segv_action, old_segv_action;    struct sigaction new_bus_action, old_bus_action;    new_segv_action.sa_handler = PointerReadFailedHandler;    new_bus_action.sa_handler = PointerReadFailedHandler;    sigemptyset(&new_segv_action.sa_mask);    sigemptyset(&new_bus_action.sa_mask);    new_segv_action.sa_flags = 0;    new_bus_action.sa_flags = 0;    sigaction (SIGSEGV, &new_segv_action, &old_segv_action);    sigaction (SIGBUS, &new_bus_action, &old_bus_action);     // The signal handler will return us to here if a signal is raised    if (sigsetjmp(sigjmp_env, 1))    {        sigaction (SIGSEGV, &old_segv_action, NULL);        sigaction (SIGBUS, &old_bus_action, NULL);        return NO;    }         Class testPointerClass = *((Class *)testPointer);     // Get the list of classes and look for testPointerClass    BOOL isClass = NO;    NSInteger numClasses = objc_getClassList(NULL, 0);    Class *classesList = malloc(sizeof(Class) * numClasses);    numClasses = objc_getClassList(classesList, numClasses);    for (int i = 0; i < numClasses; i++)    {        if (classesList[i] == testPointerClass)        {            isClass = YES;            break;        }    }    free(classesList);     // We‘re done with the signal handlers (install the previous ones)    sigaction (SIGSEGV, &old_segv_action, NULL);    sigaction (SIGBUS, &old_bus_action, NULL);         // Pointer does not point to a valid isa pointer    if (!isClass)    {        return NO;    }         // Check the allocation size    size_t allocated_size = malloc_size(testPointer);    size_t instance_size = class_getInstanceSize(testPointerClass);    if (allocated_size > instance_size)    {        *allocatedLargeEnough = YES;    }         return YES;}

 

OC checks whether the given pointer is a valid nsobject object