iOS runtime 遇到的坑

int numClasses;

Class *classes = NULL;

classes = NULL;

numClasses = objc_getClassList(NULL, 0);

NSLog(@"Number of classes: %d", numClasses);

if (numClasses > 0 )

{

classes = (__unsafe_unretained Class *)malloc(sizeof(Class) * numClasses);

numClasses = objc_getClassList(classes, numClasses);

for (int i = 0; i < numClasses; i++) {

NSLog(@"Class name: %s", class_getName(classes[i]));

const char *classname = class_getName(classes[i]);

Class cls = objc_getClass(classname);

for (int i = 0; i < numClasses; i++) {

NSLog(@"Class name: %s", class_getName(classes[i]));

const char *classname = class_getName(classes[i]);

Class cls = objc_getClass(classname);

//            if ( class_getSuperclass(class) == [GPUImageFilter class] || class_getSuperclass(class) == [GPUImageFilterGroup class] ) {

//                [filterList addObject:class];

//            }

if ([cls isSubclassOfClass:GPUImageFilter.class]) {

NSLog(@"yes");

}

}

free(classes);

}

报错[ isSubclassOfClass:]: message sent to deallocated instance，网上搜了一大堆，找不到答案，有知道的烦请交流一下。我想遍历所有类，找到某个类的所有子类。runtime也有不靠谱的时候，一般来说抱message sent to deallocated instance 是对象被释放了，这个时候还在用造成的。就这么点代码，怎么会造成过多释放？很是费解。