common: fix apk_array copying, and additional size_t fixes

src/apk_defines.h

@@ -108,6 +108,7 @@ void *apk_array_resize(void *array, size_t new_size, size_t elem_size);
 	static inline void						\
 	array_type_name##_copy(struct array_type_name **a, struct array_type_name *b)\
 	{								\
+		if (*a == b) return;					\
 		*a = apk_array_resize(*a, b->num, sizeof(elem_type_name));\
 		memcpy((*a)->item, b->item, b->num * sizeof(elem_type_name));\
 	}								\

src/common.c

@@ -10,13 +10,15 @@
 
 #include <malloc.h>
 #include <string.h>
+#include <unistd.h>
 #include "apk_defines.h"
 
 static int *dummy_array = 0;
 
 void *apk_array_resize(void *array, size_t new_size, size_t elem_size)
 {
-	int old_size, diff;
+	size_t old_size;
+	ssize_t diff;
 	void *tmp;
 
 	if (new_size == 0) {
@@ -25,7 +27,7 @@ void *apk_array_resize(void *array, size_t new_size, size_t elem_size)
 		return &dummy_array;
 	}
 
-	old_size = array ? *((int*) array) : 0;
+	old_size = array ? *((size_t *) array) : 0;
 	diff = new_size - old_size;
 
 	if (array == &dummy_array)