Question

Given a struct, e.g.

typedef struct {   int value; } TestStruct; 

Why does the following code (in the context of an Objective-C class running on the IPhone) throw a ‘non-aligned pointer being freed’ exception?

TestStruct ts = {33}; free(&ts); 

N.B. My uber goal is to use a C library with many vector-math functions, hence the need to find out some viable way to mix C and Objective-C

Answer 1

It looks to me like you’re trying to free a stack or static variable. You need to have malloc()’d something for it to be able to be free()’d.

Try this instead:

TestStruct *ts = malloc(sizeof(TestStruct)); ts->value = 33; free(ts); 

For those more familiar with object-oriented languages, you might find it helpful to create a constructor:

TestStruct *newTestStruct(int value) {     TestStruct *ret = malloc(sizeof(TestStruct));     ret->value = value;     return ret; } 

This enables you to allocate a struct and set the values in one step. Just remember that this value should be freed once it’s no longer useful:

TestStruct *x = newTestStruct(3); free(x);