Re: [PATCH] malloc: Simplify checked_request2size interface

[Siddhesh Poyarekar <siddhesh@gotplt.org>]

On 28/06/2022 17:15, Florian Weimer via Libc-alpha wrote:
> In-band signaling avoids an uninitialized variable warning when
> building with -Og and GCC 12.
> 
> Tested on i686-linux-gnu and x86_64-linux-gnu.  Built with
> build-many-glibcs.py.

LGTM.

Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

> 
> ---
>   malloc/malloc-check.c |  3 ++-
>   malloc/malloc.c       | 30 ++++++++++++++++--------------
>   2 files changed, 18 insertions(+), 15 deletions(-)
> 
> diff --git a/malloc/malloc-check.c b/malloc/malloc-check.c
> index 0299fe99a7..3368532adf 100644
> --- a/malloc/malloc-check.c
> +++ b/malloc/malloc-check.c
> @@ -275,7 +275,8 @@ realloc_check (void *oldmem, size_t bytes)
>       malloc_printerr ("realloc(): invalid pointer");
>     const INTERNAL_SIZE_T oldsize = chunksize (oldp);
>   
> -  if (!checked_request2size (rb, &chnb))
> +  chnb = checked_request2size (rb);
> +  if (chnb == 0)
>       {
>         __set_errno (ENOMEM);
>         goto invert;
> diff --git a/malloc/malloc.c b/malloc/malloc.c
> index 09e5ff2bce..12908b8f97 100644
> --- a/malloc/malloc.c
> +++ b/malloc/malloc.c
> @@ -1333,15 +1333,15 @@ nextchunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>      MINSIZE :                                                      \
>      ((req) + SIZE_SZ + MALLOC_ALIGN_MASK) & ~MALLOC_ALIGN_MASK)
>   
> -/* Check if REQ overflows when padded and aligned and if the resulting value
> -   is less than PTRDIFF_T.  Returns TRUE and the requested size or MINSIZE in
> -   case the value is less than MINSIZE on SZ or false if any of the previous
> -   check fail.  */
> -static inline bool
> -checked_request2size (size_t req, size_t *sz) __nonnull (1)
> +/* Check if REQ overflows when padded and aligned and if the resulting
> +   value is less than PTRDIFF_T.  Returns the requested size or
> +   MINSIZE in case the value is less than MINSIZE, or 0 if any of the
> +   previous checks fail.  */
> +static inline size_t
> +checked_request2size (size_t req) __nonnull (1)
>   {
>     if (__glibc_unlikely (req > PTRDIFF_MAX))
> -    return false;
> +    return 0;
>   
>     /* When using tagged memory, we cannot share the end of the user
>        block with the header for the next chunk, so ensure that we
> @@ -1359,8 +1359,7 @@ checked_request2size (size_t req, size_t *sz) __nonnull (1)
>   	    ~(size_t)(__MTAG_GRANULE_SIZE - 1);
>       }
>   
> -  *sz = request2size (req);
> -  return true;
> +  return request2size (req);
>   }
>   
>   /*
> @@ -3295,8 +3294,8 @@ __libc_malloc (size_t bytes)
>       ptmalloc_init ();
>   #if USE_TCACHE
>     /* int_free also calls request2size, be careful to not pad twice.  */
> -  size_t tbytes;
> -  if (!checked_request2size (bytes, &tbytes))
> +  size_t tbytes = checked_request2size (bytes);
> +  if (tbytes == 0)
>       {
>         __set_errno (ENOMEM);
>         return NULL;
> @@ -3443,7 +3442,8 @@ __libc_realloc (void *oldmem, size_t bytes)
>          || __builtin_expect (misaligned_chunk (oldp), 0)))
>         malloc_printerr ("realloc(): invalid pointer");
>   
> -  if (!checked_request2size (bytes, &nb))
> +  nb = checked_request2size (bytes);
> +  if (nb == 0)
>       {
>         __set_errno (ENOMEM);
>         return NULL;
> @@ -3800,7 +3800,8 @@ _int_malloc (mstate av, size_t bytes)
>        aligned.
>      */
>   
> -  if (!checked_request2size (bytes, &nb))
> +  nb = checked_request2size (bytes);
> +  if (nb == 0)
>       {
>         __set_errno (ENOMEM);
>         return NULL;
> @@ -4952,7 +4953,8 @@ _int_memalign (mstate av, size_t alignment, size_t bytes)
>   
>   
>   
> -  if (!checked_request2size (bytes, &nb))
> +  nb = checked_request2size (bytes);
> +  if (nb == 0)
>       {
>         __set_errno (ENOMEM);
>         return NULL;
>