[PATCH 2/3] xdiff: introduce XDL_CALLOC_ARRAY()

["Phillip Wood via GitGitGadget" <gitgitgadget@gmail.com>]

From: Phillip Wood <phillip.wood@dunelm.org.uk>

Add a helper for allocating an array and initialize the elements to
zero. This is analogous to CALLOC_ARRAY() in the rest of the codebase
but it returns NULL on allocation failures rather than dying to
accommodate other users of libxdiff such as libgit2.

Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
---
 xdiff/xhistogram.c | 19 ++++++-------------
 xdiff/xmacros.h    |  6 ++++++
 xdiff/xpatience.c  |  5 +----
 xdiff/xprepare.c   | 14 ++++----------
 4 files changed, 17 insertions(+), 27 deletions(-)

diff --git a/xdiff/xhistogram.c b/xdiff/xhistogram.c
index 01decffc332..df909004c10 100644
--- a/xdiff/xhistogram.c
+++ b/xdiff/xhistogram.c
@@ -251,7 +251,7 @@ static int find_lcs(xpparam_t const *xpp, xdfenv_t *env,
 		    int line1, int count1, int line2, int count2)
 {
 	int b_ptr;
-	int sz, ret = -1;
+	int ret = -1;
 	struct histindex index;
 
 	memset(&index, 0, sizeof(index));
@@ -265,23 +265,16 @@ static int find_lcs(xpparam_t const *xpp, xdfenv_t *env,
 	index.rcha.head = NULL;
 
 	index.table_bits = xdl_hashbits(count1);
-	sz = index.records_size = 1 << index.table_bits;
-	sz *= sizeof(struct record *);
-	if (!(index.records = (struct record **) xdl_malloc(sz)))
+	index.records_size = 1 << index.table_bits;
+	if (!XDL_CALLOC_ARRAY(index.records, index.records_size))
 		goto cleanup;
-	memset(index.records, 0, sz);
 
-	sz = index.line_map_size = count1;
-	sz *= sizeof(struct record *);
-	if (!(index.line_map = (struct record **) xdl_malloc(sz)))
+	index.line_map_size = count1;
+	if (!XDL_CALLOC_ARRAY(index.line_map, index.line_map_size))
 		goto cleanup;
-	memset(index.line_map, 0, sz);
 
-	sz = index.line_map_size;
-	sz *= sizeof(unsigned int);
-	if (!(index.next_ptrs = (unsigned int *) xdl_malloc(sz)))
+	if (!XDL_CALLOC_ARRAY(index.next_ptrs, index.line_map_size))
 		goto cleanup;
-	memset(index.next_ptrs, 0, sz);
 
 	/* lines / 4 + 1 comes from xprepare.c:xdl_prepare_ctx() */
 	if (xdl_cha_init(&index.rcha, sizeof(struct record), count1 / 4 + 1) < 0)
diff --git a/xdiff/xmacros.h b/xdiff/xmacros.h
index 9fd3c5da91a..23db8e785d7 100644
--- a/xdiff/xmacros.h
+++ b/xdiff/xmacros.h
@@ -55,4 +55,10 @@ do { \
 		? 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)
+
 #endif /* #if !defined(XMACROS_H) */
diff --git a/xdiff/xpatience.c b/xdiff/xpatience.c
index ce87b9084ca..fe39c2978cb 100644
--- a/xdiff/xpatience.c
+++ b/xdiff/xpatience.c
@@ -151,11 +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;
-	result->entries = (struct entry *)
-		xdl_malloc(result->alloc * sizeof(struct entry));
-	if (!result->entries)
+	if (!XDL_CALLOC_ARRAY(result->entries, result->alloc))
 		return -1;
-	memset(result->entries, 0, result->alloc * sizeof(struct entry));
 
 	/* First, fill with entries from the first file */
 	while (count1--)
diff --git a/xdiff/xprepare.c b/xdiff/xprepare.c
index 25866a1667a..b016570c488 100644
--- a/xdiff/xprepare.c
+++ b/xdiff/xprepare.c
@@ -78,12 +78,11 @@ static int xdl_init_classifier(xdlclassifier_t *cf, long size, long flags) {
 
 		return -1;
 	}
-	if (!(cf->rchash = (xdlclass_t **) xdl_malloc(cf->hsize * sizeof(xdlclass_t *)))) {
+	if (!XDL_CALLOC_ARRAY(cf->rchash, cf->hsize)) {
 
 		xdl_cha_free(&cf->ncha);
 		return -1;
 	}
-	memset(cf->rchash, 0, cf->hsize * sizeof(xdlclass_t *));
 
 	cf->alloc = size;
 	if (!XDL_ALLOC_ARRAY(cf->rcrecs, cf->alloc)) {
@@ -183,9 +182,8 @@ static int xdl_prepare_ctx(unsigned int pass, mmfile_t *mf, long narec, xpparam_
 
 	hbits = xdl_hashbits((unsigned int) narec);
 	hsize = 1 << hbits;
-	if (!(rhash = (xrecord_t **) xdl_malloc(hsize * sizeof(xrecord_t *))))
+	if (!XDL_CALLOC_ARRAY(rhash, hsize))
 		goto abort;
-	memset(rhash, 0, hsize * sizeof(xrecord_t *));
 
 	nrec = 0;
 	if ((cur = blk = xdl_mmfile_first(mf, &bsize))) {
@@ -209,9 +207,8 @@ static int xdl_prepare_ctx(unsigned int pass, mmfile_t *mf, long narec, xpparam_
 		}
 	}
 
-	if (!(rchg = (char *) xdl_malloc((nrec + 2) * sizeof(char))))
+	if (!XDL_CALLOC_ARRAY(rchg, nrec + 2))
 		goto abort;
-	memset(rchg, 0, (nrec + 2) * sizeof(char));
 
 	if ((XDF_DIFF_ALG(xpp->flags) != XDF_PATIENCE_DIFF) &&
 	    (XDF_DIFF_ALG(xpp->flags) != XDF_HISTOGRAM_DIFF)) {
@@ -383,11 +380,8 @@ static int xdl_cleanup_records(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xd
 	xdlclass_t *rcrec;
 	char *dis, *dis1, *dis2;
 
-	if (!(dis = (char *) xdl_malloc(xdf1->nrec + xdf2->nrec + 2))) {
-
+	if (!XDL_CALLOC_ARRAY(dis, xdf1->nrec + xdf2->nrec + 2))
 		return -1;
-	}
-	memset(dis, 0, xdf1->nrec + xdf2->nrec + 2);
 	dis1 = dis;
 	dis2 = dis1 + xdf1->nrec + 1;
 
-- 
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