xdiff: introduce XDL_CALLOC_ARRAY()

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>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

4 files changed, 11 insertions, 14 deletions

diff --git a/xdiff/xhistogram.c b/xdiff/xhistogram.c
index c97edc1e29..df909004c1 100644
--- a/xdiff/xhistogram.c
+++ b/xdiff/xhistogram.c
@@ -266,17 +266,14 @@ 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 (!(index.records = xdl_calloc(index.records_size,
-					 sizeof(*index.records))))
+	if (!XDL_CALLOC_ARRAY(index.records, index.records_size))
 		goto cleanup;
 
 	index.line_map_size = count1;
-	if (!(index.line_map = xdl_calloc(index.line_map_size,
-					  sizeof(*index.line_map))))
+	if (!XDL_CALLOC_ARRAY(index.line_map, index.line_map_size))
 		goto cleanup;
 
-	if (!(index.next_ptrs = xdl_calloc(index.line_map_size,
-					   sizeof(*index.next_ptrs))))
+	if (!XDL_CALLOC_ARRAY(index.next_ptrs, index.line_map_size))
 		goto cleanup;
 
 	/* lines / 4 + 1 comes from xprepare.c:xdl_prepare_ctx() */
diff --git a/xdiff/xmacros.h b/xdiff/xmacros.h
index 9fd3c5da91..0977d1615a 100644
--- a/xdiff/xmacros.h
+++ b/xdiff/xmacros.h
@@ -55,4 +55,7 @@ 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)	((p) = xdl_calloc(nr, sizeof(*(p))))
+
 #endif /* #if !defined(XMACROS_H) */
diff --git a/xdiff/xpatience.c b/xdiff/xpatience.c
index 94f8886dd1..fe39c2978c 100644
--- a/xdiff/xpatience.c
+++ b/xdiff/xpatience.c
@@ -151,8 +151,7 @@ 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 = xdl_calloc(result->alloc, sizeof(*result->entries));
-	if (!result->entries)
+	if (!XDL_CALLOC_ARRAY(result->entries, result->alloc))
 		return -1;
 
 	/* First, fill with entries from the first file */
diff --git a/xdiff/xprepare.c b/xdiff/xprepare.c
index 45190e59fc..b016570c48 100644
--- a/xdiff/xprepare.c
+++ b/xdiff/xprepare.c
@@ -78,7 +78,7 @@ static int xdl_init_classifier(xdlclassifier_t *cf, long size, long flags) {
 
 		return -1;
 	}
-	if (!(cf->rchash = xdl_calloc(cf->hsize, sizeof(*cf->rchash)))) {
+	if (!XDL_CALLOC_ARRAY(cf->rchash, cf->hsize)) {
 
 		xdl_cha_free(&cf->ncha);
 		return -1;
@@ -182,7 +182,7 @@ 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 = xdl_calloc(hsize, sizeof(*rhash))))
+	if (!XDL_CALLOC_ARRAY(rhash, hsize))
 		goto abort;
 
 	nrec = 0;
@@ -207,7 +207,7 @@ static int xdl_prepare_ctx(unsigned int pass, mmfile_t *mf, long narec, xpparam_
 		}
 	}
 
-	if (!(rchg = xdl_calloc((nrec + 2), sizeof(*rchg))))
+	if (!XDL_CALLOC_ARRAY(rchg, nrec + 2))
 		goto abort;
 
 	if ((XDF_DIFF_ALG(xpp->flags) != XDF_PATIENCE_DIFF) &&
@@ -380,10 +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 = xdl_calloc(xdf1->nrec + xdf2->nrec + 2, sizeof(*dis)))) {
-
+	if (!XDL_CALLOC_ARRAY(dis, xdf1->nrec + xdf2->nrec + 2))
 		return -1;
-	}
 	dis1 = dis;
 	dis2 = dis1 + xdf1->nrec + 1;