[PATCH 3/5] lib: fwts_alloc: avoid using void * pointer arithmetic

[Keng-Yu Lin]

On Thu, Sep 11, 2014 at 10:05 PM, Colin King <colin.king at canonical.com> wrote:
> From: Colin Ian King <colin.king at canonical.com>
>
> cppcheck reports:
>   When using void pointers in calculations, the behaviour is undefined
>
> Signed-off-by: Colin Ian King <colin.king at canonical.com>
> ---
>  src/lib/src/fwts_alloc.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/src/lib/src/fwts_alloc.c b/src/lib/src/fwts_alloc.c
> index 9610159..2a8fcd9 100644
> --- a/src/lib/src/fwts_alloc.c
> +++ b/src/lib/src/fwts_alloc.c
> @@ -19,6 +19,7 @@
>  #include <sys/mman.h>
>  #include <string.h>
>  #include <stdio.h>
> +#include <stdint.h>
>  #include <unistd.h>
>  #include <stddef.h>
>
> @@ -83,7 +84,7 @@ static void *fwts_low_mmap(const size_t requested_size)
>                 if ((first_addr_start == NULL) &&
>                     (addr_start > (void*)LIMIT_START)) {
>                         size_t sz = (requested_size + CHUNK_SIZE) & ~(CHUNK_SIZE - 1);
> -                       void *addr = addr_start - sz;
> +                       void *addr = (uint8_t*)addr_start - sz;
>
>                         /*
>                          * If addr is over the 2GB limit and we know
> @@ -108,7 +109,7 @@ static void *fwts_low_mmap(const size_t requested_size)
>                  */
>                 if ((last_addr_end != NULL) &&
>                     (last_addr_end < (void*)LIMIT_2GB)) {
> -                       if ((addr_start - last_addr_end) > (ptrdiff_t)requested_size) {
> +                       if (((uint8_t *)addr_start - (uint8_t *)last_addr_end) > (ptrdiff_t)requested_size) {
>                                 void *addr = last_addr_end;
>                                 ret = mmap(addr, requested_size, PROT_READ | PROT_WRITE,
>                                         MAP_PRIVATE | MAP_FIXED | MAP_ANONYMOUS, -1, 0);
> @@ -176,7 +177,7 @@ void *fwts_low_calloc(const size_t nmemb, const size_t size)
>         hdr->size = n;
>         hdr->magic = FWTS_ALLOC_MAGIC;
>
> -       return (ret + sizeof(fwts_mmap_header));
> +       return (void *)((uint8_t *)ret + sizeof(fwts_mmap_header));
>  }
>
>  /*
> @@ -201,7 +202,7 @@ void *fwts_low_realloc(const void *ptr, const size_t size)
>                 return fwts_low_malloc(size);
>
>         hdr = (fwts_mmap_header *)
> -               (ptr - sizeof(fwts_mmap_header));
> +               ((uint8_t *)ptr - sizeof(fwts_mmap_header));
>
>         /* sanity check */
>         if (hdr->magic != FWTS_ALLOC_MAGIC)
> @@ -224,7 +225,7 @@ void fwts_low_free(const void *ptr)
>  {
>         if (ptr) {
>                 fwts_mmap_header *hdr = (fwts_mmap_header *)
> -                       (ptr - sizeof(fwts_mmap_header));
> +                       ((uint8_t *)ptr - sizeof(fwts_mmap_header));
>                 if (hdr->magic == FWTS_ALLOC_MAGIC)
>                         munmap(hdr, hdr->size);
>         }
> --
> 2.1.0
>
>

Acked-by: Keng-Yu Lin <kengyu at canonical.com>