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Re: [libvirt] [PATCH 1/1] Implement variable length structure allocator



On 04/05/2010 11:21 AM, David Allan wrote:
> +int virAllocVar(void *ptrptr, size_t struct_size, size_t element_size, size_t count)

Shouldn't that be void **ptrptr - that is, the caller passes in the
address of a void* that we then modify?

> +{
> +    size_t alloc_size = 0;
> +
> +#if TEST_OOM
> +    if (virAllocTestFail())
> +        return -1;
> +#endif
> +
> +    if (VIR_ALLOC_VAR_OVERSIZED(struct_size, count, element_size)) {
> +        errno = ENOMEM;
> +        return -1;
> +    }
> +
> +    alloc_size = struct_size + (element_size * count);
> +    *(void **)ptrptr = calloc(1, alloc_size);
> +    if (*(void **)ptrptr == NULL)

Especially since typing it correctly to begin with would avoid these
ugly type-punning casts?

> +++ b/src/util/memory.h
> @@ -48,6 +48,10 @@
>  int virAlloc(void *ptrptr, size_t size) ATTRIBUTE_RETURN_CHECK;
>  int virAllocN(void *ptrptr, size_t size, size_t count) ATTRIBUTE_RETURN_CHECK;
>  int virReallocN(void *ptrptr, size_t size, size_t count) ATTRIBUTE_RETURN_CHECK;
> +int virAllocVar(void *ptrptr,
> +                size_t struct_size,
> +                size_t element_size,
> +                size_t count) ATTRIBUTE_RETURN_CHECK;

Then again, fixing the type for your new method would imply fixing the
typing of virAlloc and friends as well.

> +#define VIR_ALLOC_VAR(ptr, type, count) virAllocVar(&(ptr), sizeof(*ptr), sizeof(type), (count))

Should that second argument be sizeof(*(ptr)) for safety?  On the other
hand, the parenthesis around count are redundant, if you want to strip them.

-- 
Eric Blake   eblake redhat com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org

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