Re: [PATCH 4/7] xdiff: use G[C]ALLOC_ARRAY(), not XDL_CALLOC_ARRAY()

[Phillip Wood <phillip.wood123@gmail.com>]

Hi Ævar

On 08/07/2022 15:20, Ævar Arnfjörð Bjarmason wrote:
> Use the newly created GCALLOC_ARRAY() helpers rather than the recently
> introduced XDL_[C]ALLOC_ARRAY().
> 
> As shown in this diff the calling convention differs, we cannot use
> GCALLOC_ARRAY() as an expression, but that's an advantage in not
> having to relay the "sizeof()" down via a wrapper function.
> 
> This also:
> 
>   * Fixes long-standing potential overflow issues, as we're using
>     st_mult() in the underlying G_[C]ALLOC().  Note that the

What issues is this fixing? XDL_ALLOC_ARRAY() already checks for overflow.

>   * Slightly optimizes the "XDL_CALLOC_ARRAY", as we'll now use
>     calloc() rather than malloc() + memset() (although smart compilers
>     will probably do the same for both...).

That's addressed in V2 of my series, unfortunately I sent it just after 
you'd sent this series.

>   * Changes the "XDL_CALLOC_ARRAY" behavior where we'd shortcut if the
>     size was already large enough, but this behavior was changed when
>     XDL_ALLOC_ARRAY() was introduced, so this is safe.

I'm not sure what you mean here - how did we shortcut before?

> 
> Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
> ---
>   xdiff/xdiffi.c     |  3 ++-
>   xdiff/xhistogram.c |  9 ++++++---
>   xdiff/xmacros.h    | 12 ------------
>   xdiff/xpatience.c  |  6 ++++--
>   xdiff/xprepare.c   | 24 ++++++++++++++++--------
>   5 files changed, 28 insertions(+), 26 deletions(-)
> 
> diff --git a/xdiff/xdiffi.c b/xdiff/xdiffi.c
> index 6fded43e87d..077cc456087 100644
> --- a/xdiff/xdiffi.c
> +++ b/xdiff/xdiffi.c
> @@ -333,7 +333,8 @@ int xdl_do_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
>   	 * One is to store the forward path and one to store the backward path.
>   	 */
>   	ndiags = xe->xdf1.nreff + xe->xdf2.nreff + 3;
> -	if (!XDL_ALLOC_ARRAY(kvd, 2 * ndiags + 2))
> +	GALLOC_ARRAY(kvd, 2 * ndiags + 2);
> +	if (!kvd)
>   		return -1;
>   	kvdf = kvd;
>   	kvdb = kvdf + ndiags;
> diff --git a/xdiff/xhistogram.c b/xdiff/xhistogram.c
> index df909004c10..f20592bfbdd 100644
> --- a/xdiff/xhistogram.c
> +++ b/xdiff/xhistogram.c
> @@ -266,14 +266,17 @@ static int find_lcs(xpparam_t const *xpp, xdfenv_t *env,
>   
>   	index.table_bits = xdl_hashbits(count1);
>   	index.records_size = 1 << index.table_bits;
> -	if (!XDL_CALLOC_ARRAY(index.records, index.records_size))
> +	GCALLOC_ARRAY(index.records, index.records_size);
> +	if (!index.records)

I don't think that having GALLOC_ARRAY() as a statement is an 
improvement here.

Best Wishes

Phillip

>   		goto cleanup;
>   
>   	index.line_map_size = count1;
> -	if (!XDL_CALLOC_ARRAY(index.line_map, index.line_map_size))
> +	GCALLOC_ARRAY(index.line_map, index.line_map_size);
> +	if (!index.line_map)
>   		goto cleanup;
>   
> -	if (!XDL_CALLOC_ARRAY(index.next_ptrs, index.line_map_size))
> +	GCALLOC_ARRAY(index.next_ptrs, index.line_map_size);
> +	if (!index.next_ptrs)
>   		goto cleanup;
>   
>   	/* lines / 4 + 1 comes from xprepare.c:xdl_prepare_ctx() */
> diff --git a/xdiff/xmacros.h b/xdiff/xmacros.h
> index d13a6724629..75506bdf17e 100644
> --- a/xdiff/xmacros.h
> +++ b/xdiff/xmacros.h
> @@ -49,18 +49,6 @@ do { \
>   		((unsigned long) __p[2]) << 16 | ((unsigned long) __p[3]) << 24; \
>   } while (0)
>   
> -/* Allocate an array of nr elements, returns NULL on failure */
> -#define XDL_ALLOC_ARRAY(p, nr)				\
> -	((p) = SIZE_MAX / sizeof(*(p)) >= (size_t)(nr)	\
> -		? xdl_malloc((nr) * sizeof(*(p)))	\
> -		: NULL)
> -
> -/* Allocate an array of nr zeroed out elements, returns NULL on failure */
> -#define XDL_CALLOC_ARRAY(p, nr)				\
> -	(XDL_ALLOC_ARRAY((p), (nr))			\
> -		? memset((p), 0, (nr) * sizeof(*(p)))	\
> -		: NULL)
> -
>   /*
>    * Ensure array p can accommodate at least nr elements, growing the
>    * array and updating alloc (which is the number of allocated
> diff --git a/xdiff/xpatience.c b/xdiff/xpatience.c
> index fe39c2978cb..bb328d9f852 100644
> --- a/xdiff/xpatience.c
> +++ b/xdiff/xpatience.c
> @@ -151,7 +151,8 @@ static int fill_hashmap(mmfile_t *file1, mmfile_t *file2,
>   
>   	/* We know exactly how large we want the hash map */
>   	result->alloc = count1 * 2;
> -	if (!XDL_CALLOC_ARRAY(result->entries, result->alloc))
> +	GCALLOC_ARRAY(result->entries, result->alloc);
> +	if (!result->entries)
>   		return -1;
>   
>   	/* First, fill with entries from the first file */
> @@ -208,7 +209,8 @@ static int find_longest_common_sequence(struct hashmap *map, struct entry **res)
>   	 */
>   	int anchor_i = -1;
>   
> -	if (!XDL_ALLOC_ARRAY(sequence, map->nr))
> +	GALLOC_ARRAY(sequence, map->nr);
> +	if (!sequence)
>   		return -1;
>   
>   	for (entry = map->first; entry; entry = entry->next) {
> diff --git a/xdiff/xprepare.c b/xdiff/xprepare.c
> index c84549f6c50..d6cbee32a2a 100644
> --- a/xdiff/xprepare.c
> +++ b/xdiff/xprepare.c
> @@ -78,15 +78,17 @@ static int xdl_init_classifier(xdlclassifier_t *cf, long size, long flags) {
>   
>   		return -1;
>   	}
> -	if (!XDL_CALLOC_ARRAY(cf->rchash, cf->hsize)) {
> +	GCALLOC_ARRAY(cf->rchash, cf->hsize);
> +	if (!cf->rchash) {
>   
>   		xdl_cha_free(&cf->ncha);
>   		return -1;
>   	}
>   
>   	cf->alloc = size;
> -	if (!XDL_ALLOC_ARRAY(cf->rcrecs, cf->alloc)) {
>   
> +	GALLOC_ARRAY(cf->rcrecs, cf->alloc);
> +	if (!cf->rcrecs) {
>   		xdl_free(cf->rchash);
>   		xdl_cha_free(&cf->ncha);
>   		return -1;
> @@ -170,12 +172,14 @@ static int xdl_prepare_ctx(unsigned int pass, mmfile_t *mf, long narec, xpparam_
>   
>   	if (xdl_cha_init(&xdf->rcha, sizeof(xrecord_t), narec / 4 + 1) < 0)
>   		goto abort;
> -	if (!XDL_ALLOC_ARRAY(recs, narec))
> +	GALLOC_ARRAY(recs, narec);
> +	if (!recs)
>   		goto abort;
>   
>   	hbits = xdl_hashbits((unsigned int) narec);
>   	hsize = 1 << hbits;
> -	if (!XDL_CALLOC_ARRAY(rhash, hsize))
> +	GCALLOC_ARRAY(rhash, hsize);
> +	if (!rhash)
>   		goto abort;
>   
>   	nrec = 0;
> @@ -196,14 +200,17 @@ static int xdl_prepare_ctx(unsigned int pass, mmfile_t *mf, long narec, xpparam_
>   		}
>   	}
>   
> -	if (!XDL_CALLOC_ARRAY(rchg, nrec + 2))
> +	GCALLOC_ARRAY(rchg, nrec + 2);
> +	if (!rchg)
>   		goto abort;
>   
>   	if ((XDF_DIFF_ALG(xpp->flags) != XDF_PATIENCE_DIFF) &&
>   	    (XDF_DIFF_ALG(xpp->flags) != XDF_HISTOGRAM_DIFF)) {
> -		if (!XDL_ALLOC_ARRAY(rindex, nrec + 1))
> +		GALLOC_ARRAY(rindex, nrec + 1);
> +		if (!rindex)
>   			goto abort;
> -		if (!XDL_ALLOC_ARRAY(ha, nrec + 1))
> +		GALLOC_ARRAY(ha, nrec + 1);
> +		if (!ha)
>   			goto abort;
>   	}
>   
> @@ -369,7 +376,8 @@ static int xdl_cleanup_records(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xd
>   	xdlclass_t *rcrec;
>   	char *dis, *dis1, *dis2;
>   
> -	if (!XDL_CALLOC_ARRAY(dis, xdf1->nrec + xdf2->nrec + 2))
> +	GCALLOC_ARRAY(dis, xdf1->nrec + xdf2->nrec + 2);
> +	if (!dis)
>   		return -1;
>   	dis1 = dis;
>   	dis2 = dis1 + xdf1->nrec + 1;