xdiff: reduce the size of array

When the myers algorithm is selected the input files are pre-processed to remove any common prefix and suffix and any lines that appear in only one file. This requires a map to be created between the lines that are processed by the myers algorithm and the lines in the original file. That map does not include the common lines at the beginning and end of the files but the array is allocated to be the size of the whole file. Move the allocation into xdl_cleanup_records() where the map is populated and we know how big it needs to be. Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Phillip Wood committed May 4, 2026 at 15:06 UTC dca97e79bbf75f27602fe277344bfebebed82bb9
1 file changed +4 -7
xdiff/xprepare.c
+4 -7
@@ -171,12 +171,6 @@ static int xdl_prepare_ctx(unsigned int pass, mmfile_t *mf, long narec, xpparam_
171 if (!XDL_CALLOC_ARRAY(xdf->changed, xdf->nrec + 2))
172 goto abort;
173
174 - if ((XDF_DIFF_ALG(xpp->flags) != XDF_PATIENCE_DIFF) &&
175 - (XDF_DIFF_ALG(xpp->flags) != XDF_HISTOGRAM_DIFF)) {
176 - if (!XDL_ALLOC_ARRAY(xdf->reference_index, xdf->nrec + 1))
177 - goto abort;
178 - }
179 -
174 xdf->changed += 1;
175 xdf->nreff = 0;
176 xdf->dstart = 0;
@@ -283,7 +277,10 @@ static int xdl_cleanup_records(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xd
277 * changed[i] should remain false, or become true.
278 */
279 if (!XDL_CALLOC_ARRAY(action1, len1) ||
286 - !XDL_CALLOC_ARRAY(action2, len2)) {
280 + !XDL_CALLOC_ARRAY(action2, len2) ||
281 + !XDL_ALLOC_ARRAY(xdf1->reference_index, len1) ||
282 + !XDL_ALLOC_ARRAY(xdf2->reference_index, len2))
283 + {
284 ret = -1;
285 goto cleanup;
286 }