From 43d5f52ac4a3b9cb6c5717af30be42a363fedf20 Mon Sep 17 00:00:00 2001
From: Ezekiel Newren <ezekielnewren@gmail.com>
Date: Fri, 26 Sep 2025 22:41:48 +0000
Subject: [PATCH 01/12] xdiff: delete static forward declarations in xprepare

Move xdl_prepare_env() later in the file to avoid the need
for static forward declarations.

Best-viewed-with: --color-moved
Signed-off-by: Ezekiel Newren <ezekielnewren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 xdiff/xprepare.c | 116 ++++++++++++++++++++---------------------------
 1 file changed, 50 insertions(+), 66 deletions(-)

diff --git a/xdiff/xprepare.c b/xdiff/xprepare.c
index e1d4017b2d..249bfa678f 100644
--- a/xdiff/xprepare.c
+++ b/xdiff/xprepare.c
@@ -53,21 +53,6 @@ typedef struct s_xdlclassifier {
 
 
 
-static int xdl_init_classifier(xdlclassifier_t *cf, long size, long flags);
-static void xdl_free_classifier(xdlclassifier_t *cf);
-static int xdl_classify_record(unsigned int pass, xdlclassifier_t *cf, xrecord_t **rhash,
-			       unsigned int hbits, xrecord_t *rec);
-static int xdl_prepare_ctx(unsigned int pass, mmfile_t *mf, long narec, xpparam_t const *xpp,
-			   xdlclassifier_t *cf, xdfile_t *xdf);
-static void xdl_free_ctx(xdfile_t *xdf);
-static int xdl_clean_mmatch(char const *dis, long i, long s, long e);
-static int xdl_cleanup_records(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xdf2);
-static int xdl_trim_ends(xdfile_t *xdf1, xdfile_t *xdf2);
-static int xdl_optimize_ctxs(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xdf2);
-
-
-
-
 static int xdl_init_classifier(xdlclassifier_t *cf, long size, long flags) {
 	cf->flags = flags;
 
@@ -242,57 +227,6 @@ static void xdl_free_ctx(xdfile_t *xdf) {
 }
 
 
-int xdl_prepare_env(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
-		    xdfenv_t *xe) {
-	long enl1, enl2, sample;
-	xdlclassifier_t cf;
-
-	memset(&cf, 0, sizeof(cf));
-
-	/*
-	 * For histogram diff, we can afford a smaller sample size and
-	 * thus a poorer estimate of the number of lines, as the hash
-	 * table (rhash) won't be filled up/grown. The number of lines
-	 * (nrecs) will be updated correctly anyway by
-	 * xdl_prepare_ctx().
-	 */
-	sample = (XDF_DIFF_ALG(xpp->flags) == XDF_HISTOGRAM_DIFF
-		  ? XDL_GUESS_NLINES2 : XDL_GUESS_NLINES1);
-
-	enl1 = xdl_guess_lines(mf1, sample) + 1;
-	enl2 = xdl_guess_lines(mf2, sample) + 1;
-
-	if (xdl_init_classifier(&cf, enl1 + enl2 + 1, xpp->flags) < 0)
-		return -1;
-
-	if (xdl_prepare_ctx(1, mf1, enl1, xpp, &cf, &xe->xdf1) < 0) {
-
-		xdl_free_classifier(&cf);
-		return -1;
-	}
-	if (xdl_prepare_ctx(2, mf2, enl2, xpp, &cf, &xe->xdf2) < 0) {
-
-		xdl_free_ctx(&xe->xdf1);
-		xdl_free_classifier(&cf);
-		return -1;
-	}
-
-	if ((XDF_DIFF_ALG(xpp->flags) != XDF_PATIENCE_DIFF) &&
-	    (XDF_DIFF_ALG(xpp->flags) != XDF_HISTOGRAM_DIFF) &&
-	    xdl_optimize_ctxs(&cf, &xe->xdf1, &xe->xdf2) < 0) {
-
-		xdl_free_ctx(&xe->xdf2);
-		xdl_free_ctx(&xe->xdf1);
-		xdl_free_classifier(&cf);
-		return -1;
-	}
-
-	xdl_free_classifier(&cf);
-
-	return 0;
-}
-
-
 void xdl_free_env(xdfenv_t *xe) {
 
 	xdl_free_ctx(&xe->xdf2);
@@ -460,3 +394,53 @@ static int xdl_optimize_ctxs(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xdf2
 
 	return 0;
 }
+
+int xdl_prepare_env(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
+		    xdfenv_t *xe) {
+	long enl1, enl2, sample;
+	xdlclassifier_t cf;
+
+	memset(&cf, 0, sizeof(cf));
+
+	/*
+	 * For histogram diff, we can afford a smaller sample size and
+	 * thus a poorer estimate of the number of lines, as the hash
+	 * table (rhash) won't be filled up/grown. The number of lines
+	 * (nrecs) will be updated correctly anyway by
+	 * xdl_prepare_ctx().
+	 */
+	sample = (XDF_DIFF_ALG(xpp->flags) == XDF_HISTOGRAM_DIFF
+		  ? XDL_GUESS_NLINES2 : XDL_GUESS_NLINES1);
+
+	enl1 = xdl_guess_lines(mf1, sample) + 1;
+	enl2 = xdl_guess_lines(mf2, sample) + 1;
+
+	if (xdl_init_classifier(&cf, enl1 + enl2 + 1, xpp->flags) < 0)
+		return -1;
+
+	if (xdl_prepare_ctx(1, mf1, enl1, xpp, &cf, &xe->xdf1) < 0) {
+
+		xdl_free_classifier(&cf);
+		return -1;
+	}
+	if (xdl_prepare_ctx(2, mf2, enl2, xpp, &cf, &xe->xdf2) < 0) {
+
+		xdl_free_ctx(&xe->xdf1);
+		xdl_free_classifier(&cf);
+		return -1;
+	}
+
+	if ((XDF_DIFF_ALG(xpp->flags) != XDF_PATIENCE_DIFF) &&
+	    (XDF_DIFF_ALG(xpp->flags) != XDF_HISTOGRAM_DIFF) &&
+	    xdl_optimize_ctxs(&cf, &xe->xdf1, &xe->xdf2) < 0) {
+
+		xdl_free_ctx(&xe->xdf2);
+		xdl_free_ctx(&xe->xdf1);
+		xdl_free_classifier(&cf);
+		return -1;
+	}
+
+	xdl_free_classifier(&cf);
+
+	return 0;
+}

From d1c028bdf75b9bcd380f85f74a34edcbaa060fee Mon Sep 17 00:00:00 2001
From: Ezekiel Newren <ezekielnewren@gmail.com>
Date: Fri, 26 Sep 2025 22:41:49 +0000
Subject: [PATCH 02/12] xdiff: delete local variables and initialize/free
 xdfile_t directly

These local variables are essentially a hand-rolled additional
implementation of xdl_free_ctx() inlined into xdl_prepare_ctx(). Modify
the code to use the existing xdl_free_ctx() function so there aren't
two ways to free such variables.

Signed-off-by: Ezekiel Newren <ezekielnewren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 xdiff/xprepare.c | 150 +++++++++++++++++++++--------------------------
 1 file changed, 66 insertions(+), 84 deletions(-)

diff --git a/xdiff/xprepare.c b/xdiff/xprepare.c
index 249bfa678f..96134c9fbf 100644
--- a/xdiff/xprepare.c
+++ b/xdiff/xprepare.c
@@ -134,90 +134,8 @@ static int xdl_classify_record(unsigned int pass, xdlclassifier_t *cf, xrecord_t
 }
 
 
-static int xdl_prepare_ctx(unsigned int pass, mmfile_t *mf, long narec, xpparam_t const *xpp,
-			   xdlclassifier_t *cf, xdfile_t *xdf) {
-	unsigned int hbits;
-	long nrec, hsize, bsize;
-	unsigned long hav;
-	char const *blk, *cur, *top, *prev;
-	xrecord_t *crec;
-	xrecord_t **recs;
-	xrecord_t **rhash;
-	unsigned long *ha;
-	char *rchg;
-	long *rindex;
-
-	ha = NULL;
-	rindex = NULL;
-	rchg = NULL;
-	rhash = NULL;
-	recs = NULL;
-
-	if (xdl_cha_init(&xdf->rcha, sizeof(xrecord_t), narec / 4 + 1) < 0)
-		goto abort;
-	if (!XDL_ALLOC_ARRAY(recs, narec))
-		goto abort;
-
-	hbits = xdl_hashbits((unsigned int) narec);
-	hsize = 1 << hbits;
-	if (!XDL_CALLOC_ARRAY(rhash, hsize))
-		goto abort;
-
-	nrec = 0;
-	if ((cur = blk = xdl_mmfile_first(mf, &bsize))) {
-		for (top = blk + bsize; cur < top; ) {
-			prev = cur;
-			hav = xdl_hash_record(&cur, top, xpp->flags);
-			if (XDL_ALLOC_GROW(recs, nrec + 1, narec))
-				goto abort;
-			if (!(crec = xdl_cha_alloc(&xdf->rcha)))
-				goto abort;
-			crec->ptr = prev;
-			crec->size = (long) (cur - prev);
-			crec->ha = hav;
-			recs[nrec++] = crec;
-			if (xdl_classify_record(pass, cf, rhash, hbits, crec) < 0)
-				goto abort;
-		}
-	}
-
-	if (!XDL_CALLOC_ARRAY(rchg, nrec + 2))
-		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))
-			goto abort;
-		if (!XDL_ALLOC_ARRAY(ha, nrec + 1))
-			goto abort;
-	}
-
-	xdf->nrec = nrec;
-	xdf->recs = recs;
-	xdf->hbits = hbits;
-	xdf->rhash = rhash;
-	xdf->rchg = rchg + 1;
-	xdf->rindex = rindex;
-	xdf->nreff = 0;
-	xdf->ha = ha;
-	xdf->dstart = 0;
-	xdf->dend = nrec - 1;
-
-	return 0;
-
-abort:
-	xdl_free(ha);
-	xdl_free(rindex);
-	xdl_free(rchg);
-	xdl_free(rhash);
-	xdl_free(recs);
-	xdl_cha_free(&xdf->rcha);
-	return -1;
-}
-
-
-static void xdl_free_ctx(xdfile_t *xdf) {
-
+static void xdl_free_ctx(xdfile_t *xdf)
+{
 	xdl_free(xdf->rhash);
 	xdl_free(xdf->rindex);
 	xdl_free(xdf->rchg - 1);
@@ -227,6 +145,70 @@ static void xdl_free_ctx(xdfile_t *xdf) {
 }
 
 
+static int xdl_prepare_ctx(unsigned int pass, mmfile_t *mf, long narec, xpparam_t const *xpp,
+			   xdlclassifier_t *cf, xdfile_t *xdf) {
+	long bsize;
+	unsigned long hav;
+	char const *blk, *cur, *top, *prev;
+	xrecord_t *crec;
+
+	xdf->ha = NULL;
+	xdf->rindex = NULL;
+	xdf->rchg = NULL;
+	xdf->rhash = NULL;
+	xdf->recs = NULL;
+
+	if (xdl_cha_init(&xdf->rcha, sizeof(xrecord_t), narec / 4 + 1) < 0)
+		goto abort;
+	if (!XDL_ALLOC_ARRAY(xdf->recs, narec))
+		goto abort;
+
+	xdf->hbits = xdl_hashbits((unsigned int) narec);
+	if (!XDL_CALLOC_ARRAY(xdf->rhash, 1 << xdf->hbits))
+		goto abort;
+
+	xdf->nrec = 0;
+	if ((cur = blk = xdl_mmfile_first(mf, &bsize))) {
+		for (top = blk + bsize; cur < top; ) {
+			prev = cur;
+			hav = xdl_hash_record(&cur, top, xpp->flags);
+			if (XDL_ALLOC_GROW(xdf->recs, xdf->nrec + 1, narec))
+				goto abort;
+			if (!(crec = xdl_cha_alloc(&xdf->rcha)))
+				goto abort;
+			crec->ptr = prev;
+			crec->size = (long) (cur - prev);
+			crec->ha = hav;
+			xdf->recs[xdf->nrec++] = crec;
+			if (xdl_classify_record(pass, cf, xdf->rhash, xdf->hbits, crec) < 0)
+				goto abort;
+		}
+	}
+
+	if (!XDL_CALLOC_ARRAY(xdf->rchg, xdf->nrec + 2))
+		goto abort;
+
+	if ((XDF_DIFF_ALG(xpp->flags) != XDF_PATIENCE_DIFF) &&
+	    (XDF_DIFF_ALG(xpp->flags) != XDF_HISTOGRAM_DIFF)) {
+		if (!XDL_ALLOC_ARRAY(xdf->rindex, xdf->nrec + 1))
+			goto abort;
+		if (!XDL_ALLOC_ARRAY(xdf->ha, xdf->nrec + 1))
+			goto abort;
+	}
+
+	xdf->rchg += 1;
+	xdf->nreff = 0;
+	xdf->dstart = 0;
+	xdf->dend = xdf->nrec - 1;
+
+	return 0;
+
+abort:
+	xdl_free_ctx(xdf);
+	return -1;
+}
+
+
 void xdl_free_env(xdfenv_t *xe) {
 
 	xdl_free_ctx(&xe->xdf2);

From efaf553b1a4ea9cafcb9cab0697157091bc4825a Mon Sep 17 00:00:00 2001
From: Ezekiel Newren <ezekielnewren@gmail.com>
Date: Fri, 26 Sep 2025 22:41:50 +0000
Subject: [PATCH 03/12] xdiff: delete unnecessary fields from xrecord_t and
 xdfile_t

xrecord_t.next, xdfile_t.hbits, xdfile_t.rhash are initialized,
but never used for anything by the code. Remove them.

Best-viewed-with: --color-words
Signed-off-by: Ezekiel Newren <ezekielnewren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 xdiff/xprepare.c | 15 ++-------------
 xdiff/xtypes.h   |  3 ---
 2 files changed, 2 insertions(+), 16 deletions(-)

diff --git a/xdiff/xprepare.c b/xdiff/xprepare.c
index 96134c9fbf..3576415c85 100644
--- a/xdiff/xprepare.c
+++ b/xdiff/xprepare.c
@@ -91,8 +91,7 @@ static void xdl_free_classifier(xdlclassifier_t *cf) {
 }
 
 
-static int xdl_classify_record(unsigned int pass, xdlclassifier_t *cf, xrecord_t **rhash,
-			       unsigned int hbits, xrecord_t *rec) {
+static int xdl_classify_record(unsigned int pass, xdlclassifier_t *cf, xrecord_t *rec) {
 	long hi;
 	char const *line;
 	xdlclass_t *rcrec;
@@ -126,17 +125,12 @@ static int xdl_classify_record(unsigned int pass, xdlclassifier_t *cf, xrecord_t
 
 	rec->ha = (unsigned long) rcrec->idx;
 
-	hi = (long) XDL_HASHLONG(rec->ha, hbits);
-	rec->next = rhash[hi];
-	rhash[hi] = rec;
-
 	return 0;
 }
 
 
 static void xdl_free_ctx(xdfile_t *xdf)
 {
-	xdl_free(xdf->rhash);
 	xdl_free(xdf->rindex);
 	xdl_free(xdf->rchg - 1);
 	xdl_free(xdf->ha);
@@ -155,7 +149,6 @@ static int xdl_prepare_ctx(unsigned int pass, mmfile_t *mf, long narec, xpparam_
 	xdf->ha = NULL;
 	xdf->rindex = NULL;
 	xdf->rchg = NULL;
-	xdf->rhash = NULL;
 	xdf->recs = NULL;
 
 	if (xdl_cha_init(&xdf->rcha, sizeof(xrecord_t), narec / 4 + 1) < 0)
@@ -163,10 +156,6 @@ static int xdl_prepare_ctx(unsigned int pass, mmfile_t *mf, long narec, xpparam_
 	if (!XDL_ALLOC_ARRAY(xdf->recs, narec))
 		goto abort;
 
-	xdf->hbits = xdl_hashbits((unsigned int) narec);
-	if (!XDL_CALLOC_ARRAY(xdf->rhash, 1 << xdf->hbits))
-		goto abort;
-
 	xdf->nrec = 0;
 	if ((cur = blk = xdl_mmfile_first(mf, &bsize))) {
 		for (top = blk + bsize; cur < top; ) {
@@ -180,7 +169,7 @@ static int xdl_prepare_ctx(unsigned int pass, mmfile_t *mf, long narec, xpparam_
 			crec->size = (long) (cur - prev);
 			crec->ha = hav;
 			xdf->recs[xdf->nrec++] = crec;
-			if (xdl_classify_record(pass, cf, xdf->rhash, xdf->hbits, crec) < 0)
+			if (xdl_classify_record(pass, cf, crec) < 0)
 				goto abort;
 		}
 	}
diff --git a/xdiff/xtypes.h b/xdiff/xtypes.h
index 8442bd436e..8b8467360e 100644
--- a/xdiff/xtypes.h
+++ b/xdiff/xtypes.h
@@ -39,7 +39,6 @@ typedef struct s_chastore {
 } chastore_t;
 
 typedef struct s_xrecord {
-	struct s_xrecord *next;
 	char const *ptr;
 	long size;
 	unsigned long ha;
@@ -48,8 +47,6 @@ typedef struct s_xrecord {
 typedef struct s_xdfile {
 	chastore_t rcha;
 	long nrec;
-	unsigned int hbits;
-	xrecord_t **rhash;
 	long dstart, dend;
 	xrecord_t **recs;
 	char *rchg;

From 7bdeb3afad908e52baab6e58397423aa2d2f3d29 Mon Sep 17 00:00:00 2001
From: Ezekiel Newren <ezekielnewren@gmail.com>
Date: Fri, 26 Sep 2025 22:41:51 +0000
Subject: [PATCH 04/12] xdiff: delete superfluous function xdl_get_rec() in
 xemit

When xrecord_t was a linked list, and recs didn't exist, I assume this
function walked the list until it found the right record. Accessing
a contiguous array is so trivial that this function is now superfluous.
Delete it.

Signed-off-by: Ezekiel Newren <ezekielnewren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 xdiff/xemit.c | 23 +++++++----------------
 1 file changed, 7 insertions(+), 16 deletions(-)

diff --git a/xdiff/xemit.c b/xdiff/xemit.c
index 1d40c9cb40..40fc8154f3 100644
--- a/xdiff/xemit.c
+++ b/xdiff/xemit.c
@@ -22,23 +22,14 @@
 
 #include "xinclude.h"
 
-static long xdl_get_rec(xdfile_t *xdf, long ri, char const **rec) {
-
-	*rec = xdf->recs[ri]->ptr;
-
-	return xdf->recs[ri]->size;
-}
-
 
 static int xdl_emit_record(xdfile_t *xdf, long ri, char const *pre, xdemitcb_t *ecb) {
 	long size, psize = strlen(pre);
-	char const *rec;
-
-	size = xdl_get_rec(xdf, ri, &rec);
-	if (xdl_emit_diffrec(rec, size, pre, psize, ecb) < 0) {
+	char const *rec = xdf->recs[ri]->ptr;
 
+	size = xdf->recs[ri]->size;
+	if (xdl_emit_diffrec(rec, size, pre, psize, ecb) < 0)
 		return -1;
-	}
 
 	return 0;
 }
@@ -120,8 +111,8 @@ static long def_ff(const char *rec, long len, char *buf, long sz)
 static long match_func_rec(xdfile_t *xdf, xdemitconf_t const *xecfg, long ri,
 			   char *buf, long sz)
 {
-	const char *rec;
-	long len = xdl_get_rec(xdf, ri, &rec);
+	const char *rec = xdf->recs[ri]->ptr;
+	long len = xdf->recs[ri]->size;
 	if (!xecfg->find_func)
 		return def_ff(rec, len, buf, sz);
 	return xecfg->find_func(rec, len, buf, sz, xecfg->find_func_priv);
@@ -160,8 +151,8 @@ static long get_func_line(xdfenv_t *xe, xdemitconf_t const *xecfg,
 
 static int is_empty_rec(xdfile_t *xdf, long ri)
 {
-	const char *rec;
-	long len = xdl_get_rec(xdf, ri, &rec);
+	const char *rec = xdf->recs[ri]->ptr;
+	long len = xdf->recs[ri]->size;
 
 	while (len > 0 && XDL_ISSPACE(*rec)) {
 		rec++;

From 7c6ce2e47b274b299dd0a3b185e70f2ee5e3e07a Mon Sep 17 00:00:00 2001
From: Ezekiel Newren <ezekielnewren@gmail.com>
Date: Fri, 26 Sep 2025 22:41:52 +0000
Subject: [PATCH 05/12] xdiff: delete local variables that alias fields in
 xrecord_t

Use the type xrecord_t as the local variable for the functions in the
file xdiff/xemit.c. Most places directly reference the fields inside of
this struct, doing that here makes it more consistent with the rest of
the code.

Signed-off-by: Ezekiel Newren <ezekielnewren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 xdiff/xemit.c | 29 +++++++++++++----------------
 1 file changed, 13 insertions(+), 16 deletions(-)

diff --git a/xdiff/xemit.c b/xdiff/xemit.c
index 40fc8154f3..2161ac3cd0 100644
--- a/xdiff/xemit.c
+++ b/xdiff/xemit.c
@@ -23,12 +23,11 @@
 #include "xinclude.h"
 
 
-static int xdl_emit_record(xdfile_t *xdf, long ri, char const *pre, xdemitcb_t *ecb) {
-	long size, psize = strlen(pre);
-	char const *rec = xdf->recs[ri]->ptr;
+static int xdl_emit_record(xdfile_t *xdf, long ri, char const *pre, xdemitcb_t *ecb)
+{
+	xrecord_t *rec = xdf->recs[ri];
 
-	size = xdf->recs[ri]->size;
-	if (xdl_emit_diffrec(rec, size, pre, psize, ecb) < 0)
+	if (xdl_emit_diffrec(rec->ptr, rec->size, pre, strlen(pre), ecb) < 0)
 		return -1;
 
 	return 0;
@@ -111,11 +110,11 @@ static long def_ff(const char *rec, long len, char *buf, long sz)
 static long match_func_rec(xdfile_t *xdf, xdemitconf_t const *xecfg, long ri,
 			   char *buf, long sz)
 {
-	const char *rec = xdf->recs[ri]->ptr;
-	long len = xdf->recs[ri]->size;
+	xrecord_t *rec = xdf->recs[ri];
+
 	if (!xecfg->find_func)
-		return def_ff(rec, len, buf, sz);
-	return xecfg->find_func(rec, len, buf, sz, xecfg->find_func_priv);
+		return def_ff(rec->ptr, rec->size, buf, sz);
+	return xecfg->find_func(rec->ptr, rec->size, buf, sz, xecfg->find_func_priv);
 }
 
 static int is_func_rec(xdfile_t *xdf, xdemitconf_t const *xecfg, long ri)
@@ -151,14 +150,12 @@ static long get_func_line(xdfenv_t *xe, xdemitconf_t const *xecfg,
 
 static int is_empty_rec(xdfile_t *xdf, long ri)
 {
-	const char *rec = xdf->recs[ri]->ptr;
-	long len = xdf->recs[ri]->size;
+	xrecord_t *rec = xdf->recs[ri];
+	long i = 0;
 
-	while (len > 0 && XDL_ISSPACE(*rec)) {
-		rec++;
-		len--;
-	}
-	return !len;
+	for (; i < rec->size && XDL_ISSPACE(rec->ptr[i]); i++);
+
+	return i == rec->size;
 }
 
 int xdl_emit_diff(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,

From f4ea812b2d930fb1825b99dc11ca186691dade99 Mon Sep 17 00:00:00 2001
From: Ezekiel Newren <ezekielnewren@gmail.com>
Date: Fri, 26 Sep 2025 22:41:53 +0000
Subject: [PATCH 06/12] xdiff: delete struct diffdata_t

Every field in this struct is an alias for a certain field in xdfile_t.

diffdata_t.nrec   -> xdfile_t.nreff
diffdata_t.ha     -> xdfile_t.ha
diffdata_t.rindex -> xdfile_t.rindex
diffdata_t.rchg   -> xdfile_t.rchg

I think this struct existed before xdfile_t, and was kept for backward
compatibility reasons. I think xdiffi should have been refactored to
use the new (xdfile_t) struct, but was easier to alias it instead.

The local variables rchg* and rindex* don't shorten the lines by much,
nor do they really need to be there to make the code more readable.
Delete them.

Signed-off-by: Ezekiel Newren <ezekielnewren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 xdiff/xdiffi.c | 32 ++++++++------------------------
 xdiff/xdiffi.h | 11 ++---------
 2 files changed, 10 insertions(+), 33 deletions(-)

diff --git a/xdiff/xdiffi.c b/xdiff/xdiffi.c
index 5a96e36dfb..bbf0161f84 100644
--- a/xdiff/xdiffi.c
+++ b/xdiff/xdiffi.c
@@ -257,10 +257,10 @@ static long xdl_split(unsigned long const *ha1, long off1, long lim1,
  * sub-boxes by calling the box splitting function. Note that the real job
  * (marking changed lines) is done in the two boundary reaching checks.
  */
-int xdl_recs_cmp(diffdata_t *dd1, long off1, long lim1,
-		 diffdata_t *dd2, long off2, long lim2,
+int xdl_recs_cmp(xdfile_t *xdf1, long off1, long lim1,
+		 xdfile_t *xdf2, long off2, long lim2,
 		 long *kvdf, long *kvdb, int need_min, xdalgoenv_t *xenv) {
-	unsigned long const *ha1 = dd1->ha, *ha2 = dd2->ha;
+	unsigned long const *ha1 = xdf1->ha, *ha2 = xdf2->ha;
 
 	/*
 	 * Shrink the box by walking through each diagonal snake (SW and NE).
@@ -273,17 +273,11 @@ int xdl_recs_cmp(diffdata_t *dd1, long off1, long lim1,
 	 * be obviously changed.
 	 */
 	if (off1 == lim1) {
-		char *rchg2 = dd2->rchg;
-		long *rindex2 = dd2->rindex;
-
 		for (; off2 < lim2; off2++)
-			rchg2[rindex2[off2]] = 1;
+			xdf2->rchg[xdf2->rindex[off2]] = 1;
 	} else if (off2 == lim2) {
-		char *rchg1 = dd1->rchg;
-		long *rindex1 = dd1->rindex;
-
 		for (; off1 < lim1; off1++)
-			rchg1[rindex1[off1]] = 1;
+			xdf1->rchg[xdf1->rindex[off1]] = 1;
 	} else {
 		xdpsplit_t spl;
 		spl.i1 = spl.i2 = 0;
@@ -300,9 +294,9 @@ int xdl_recs_cmp(diffdata_t *dd1, long off1, long lim1,
 		/*
 		 * ... et Impera.
 		 */
-		if (xdl_recs_cmp(dd1, off1, spl.i1, dd2, off2, spl.i2,
+		if (xdl_recs_cmp(xdf1, off1, spl.i1, xdf2, off2, spl.i2,
 				 kvdf, kvdb, spl.min_lo, xenv) < 0 ||
-		    xdl_recs_cmp(dd1, spl.i1, lim1, dd2, spl.i2, lim2,
+		    xdl_recs_cmp(xdf1, spl.i1, lim1, xdf2, spl.i2, lim2,
 				 kvdf, kvdb, spl.min_hi, xenv) < 0) {
 
 			return -1;
@@ -318,7 +312,6 @@ int xdl_do_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
 	long ndiags;
 	long *kvd, *kvdf, *kvdb;
 	xdalgoenv_t xenv;
-	diffdata_t dd1, dd2;
 	int res;
 
 	if (xdl_prepare_env(mf1, mf2, xpp, xe) < 0)
@@ -357,16 +350,7 @@ int xdl_do_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
 	xenv.snake_cnt = XDL_SNAKE_CNT;
 	xenv.heur_min = XDL_HEUR_MIN_COST;
 
-	dd1.nrec = xe->xdf1.nreff;
-	dd1.ha = xe->xdf1.ha;
-	dd1.rchg = xe->xdf1.rchg;
-	dd1.rindex = xe->xdf1.rindex;
-	dd2.nrec = xe->xdf2.nreff;
-	dd2.ha = xe->xdf2.ha;
-	dd2.rchg = xe->xdf2.rchg;
-	dd2.rindex = xe->xdf2.rindex;
-
-	res = xdl_recs_cmp(&dd1, 0, dd1.nrec, &dd2, 0, dd2.nrec,
+	res = xdl_recs_cmp(&xe->xdf1, 0, xe->xdf1.nreff, &xe->xdf2, 0, xe->xdf2.nreff,
 			   kvdf, kvdb, (xpp->flags & XDF_NEED_MINIMAL) != 0,
 			   &xenv);
 	xdl_free(kvd);
diff --git a/xdiff/xdiffi.h b/xdiff/xdiffi.h
index 126c9d8ff4..49e52c67f9 100644
--- a/xdiff/xdiffi.h
+++ b/xdiff/xdiffi.h
@@ -24,13 +24,6 @@
 #define XDIFFI_H
 
 
-typedef struct s_diffdata {
-	long nrec;
-	unsigned long const *ha;
-	long *rindex;
-	char *rchg;
-} diffdata_t;
-
 typedef struct s_xdalgoenv {
 	long mxcost;
 	long snake_cnt;
@@ -46,8 +39,8 @@ typedef struct s_xdchange {
 
 
 
-int xdl_recs_cmp(diffdata_t *dd1, long off1, long lim1,
-		 diffdata_t *dd2, long off2, long lim2,
+int xdl_recs_cmp(xdfile_t *xdf1, long off1, long lim1,
+		 xdfile_t *xdf2, long off2, long lim2,
 		 long *kvdf, long *kvdb, int need_min, xdalgoenv_t *xenv);
 int xdl_do_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
 		xdfenv_t *xe);

From 5c294dceb23633a8bcced946ce3f65a06038cf52 Mon Sep 17 00:00:00 2001
From: Ezekiel Newren <ezekielnewren@gmail.com>
Date: Fri, 26 Sep 2025 22:41:54 +0000
Subject: [PATCH 07/12] xdiff: delete redundant array xdfile_t.ha

When 0 <= i < xdfile_t.nreff the following is true:
xdfile_t.ha[i] == xdfile_t.recs[xdfile_t.rindex[i]]

This makes the code about 5% slower. The fields rindex and ha are
specific to the classic diff (myers and minimal). I plan on creating a
struct for classic diff, but there's a lot of cleanup that needs to be
done before that can happen and leaving ha in would make those cleanups
harder to follow.

A subsequent commit will delete the chastore cha from xdfile_t. That
later commit will investigate deleting ha and cha independently and
together.

Signed-off-by: Ezekiel Newren <ezekielnewren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 xdiff/xdiffi.c   | 24 ++++++++++++++----------
 xdiff/xprepare.c | 12 ++----------
 xdiff/xtypes.h   |  1 -
 3 files changed, 16 insertions(+), 21 deletions(-)

diff --git a/xdiff/xdiffi.c b/xdiff/xdiffi.c
index bbf0161f84..11cd090b53 100644
--- a/xdiff/xdiffi.c
+++ b/xdiff/xdiffi.c
@@ -22,6 +22,11 @@
 
 #include "xinclude.h"
 
+static unsigned long get_hash(xdfile_t *xdf, long index)
+{
+	return xdf->recs[xdf->rindex[index]]->ha;
+}
+
 #define XDL_MAX_COST_MIN 256
 #define XDL_HEUR_MIN_COST 256
 #define XDL_LINE_MAX (long)((1UL << (CHAR_BIT * sizeof(long) - 1)) - 1)
@@ -42,8 +47,8 @@ typedef struct s_xdpsplit {
  * using this algorithm, so a little bit of heuristic is needed to cut the
  * search and to return a suboptimal point.
  */
-static long xdl_split(unsigned long const *ha1, long off1, long lim1,
-		      unsigned long const *ha2, long off2, long lim2,
+static long xdl_split(xdfile_t *xdf1, long off1, long lim1,
+		      xdfile_t *xdf2, long off2, long lim2,
 		      long *kvdf, long *kvdb, int need_min, xdpsplit_t *spl,
 		      xdalgoenv_t *xenv) {
 	long dmin = off1 - lim2, dmax = lim1 - off2;
@@ -87,7 +92,7 @@ static long xdl_split(unsigned long const *ha1, long off1, long lim1,
 				i1 = kvdf[d + 1];
 			prev1 = i1;
 			i2 = i1 - d;
-			for (; i1 < lim1 && i2 < lim2 && ha1[i1] == ha2[i2]; i1++, i2++);
+			for (; i1 < lim1 && i2 < lim2 && get_hash(xdf1, i1) == get_hash(xdf2, i2); i1++, i2++);
 			if (i1 - prev1 > xenv->snake_cnt)
 				got_snake = 1;
 			kvdf[d] = i1;
@@ -124,7 +129,7 @@ static long xdl_split(unsigned long const *ha1, long off1, long lim1,
 				i1 = kvdb[d + 1] - 1;
 			prev1 = i1;
 			i2 = i1 - d;
-			for (; i1 > off1 && i2 > off2 && ha1[i1 - 1] == ha2[i2 - 1]; i1--, i2--);
+			for (; i1 > off1 && i2 > off2 && get_hash(xdf1, i1 - 1) == get_hash(xdf2, i2 - 1); i1--, i2--);
 			if (prev1 - i1 > xenv->snake_cnt)
 				got_snake = 1;
 			kvdb[d] = i1;
@@ -159,7 +164,7 @@ static long xdl_split(unsigned long const *ha1, long off1, long lim1,
 				if (v > XDL_K_HEUR * ec && v > best &&
 				    off1 + xenv->snake_cnt <= i1 && i1 < lim1 &&
 				    off2 + xenv->snake_cnt <= i2 && i2 < lim2) {
-					for (k = 1; ha1[i1 - k] == ha2[i2 - k]; k++)
+					for (k = 1; get_hash(xdf1, i1 - k) == get_hash(xdf2, i2 - k); k++)
 						if (k == xenv->snake_cnt) {
 							best = v;
 							spl->i1 = i1;
@@ -183,7 +188,7 @@ static long xdl_split(unsigned long const *ha1, long off1, long lim1,
 				if (v > XDL_K_HEUR * ec && v > best &&
 				    off1 < i1 && i1 <= lim1 - xenv->snake_cnt &&
 				    off2 < i2 && i2 <= lim2 - xenv->snake_cnt) {
-					for (k = 0; ha1[i1 + k] == ha2[i2 + k]; k++)
+					for (k = 0; get_hash(xdf1, i1 + k) == get_hash(xdf2, i2 + k); k++)
 						if (k == xenv->snake_cnt - 1) {
 							best = v;
 							spl->i1 = i1;
@@ -260,13 +265,12 @@ static long xdl_split(unsigned long const *ha1, long off1, long lim1,
 int xdl_recs_cmp(xdfile_t *xdf1, long off1, long lim1,
 		 xdfile_t *xdf2, long off2, long lim2,
 		 long *kvdf, long *kvdb, int need_min, xdalgoenv_t *xenv) {
-	unsigned long const *ha1 = xdf1->ha, *ha2 = xdf2->ha;
 
 	/*
 	 * Shrink the box by walking through each diagonal snake (SW and NE).
 	 */
-	for (; off1 < lim1 && off2 < lim2 && ha1[off1] == ha2[off2]; off1++, off2++);
-	for (; off1 < lim1 && off2 < lim2 && ha1[lim1 - 1] == ha2[lim2 - 1]; lim1--, lim2--);
+	for (; off1 < lim1 && off2 < lim2 && get_hash(xdf1, off1) == get_hash(xdf2, off2); off1++, off2++);
+	for (; off1 < lim1 && off2 < lim2 && get_hash(xdf1, lim1 - 1) == get_hash(xdf2, lim2 - 1); lim1--, lim2--);
 
 	/*
 	 * If one dimension is empty, then all records on the other one must
@@ -285,7 +289,7 @@ int xdl_recs_cmp(xdfile_t *xdf1, long off1, long lim1,
 		/*
 		 * Divide ...
 		 */
-		if (xdl_split(ha1, off1, lim1, ha2, off2, lim2, kvdf, kvdb,
+		if (xdl_split(xdf1, off1, lim1, xdf2, off2, lim2, kvdf, kvdb,
 			      need_min, &spl, xenv) < 0) {
 
 			return -1;
diff --git a/xdiff/xprepare.c b/xdiff/xprepare.c
index 3576415c85..22c44f0683 100644
--- a/xdiff/xprepare.c
+++ b/xdiff/xprepare.c
@@ -133,7 +133,6 @@ static void xdl_free_ctx(xdfile_t *xdf)
 {
 	xdl_free(xdf->rindex);
 	xdl_free(xdf->rchg - 1);
-	xdl_free(xdf->ha);
 	xdl_free(xdf->recs);
 	xdl_cha_free(&xdf->rcha);
 }
@@ -146,7 +145,6 @@ static int xdl_prepare_ctx(unsigned int pass, mmfile_t *mf, long narec, xpparam_
 	char const *blk, *cur, *top, *prev;
 	xrecord_t *crec;
 
-	xdf->ha = NULL;
 	xdf->rindex = NULL;
 	xdf->rchg = NULL;
 	xdf->recs = NULL;
@@ -181,8 +179,6 @@ static int xdl_prepare_ctx(unsigned int pass, mmfile_t *mf, long narec, xpparam_
 	    (XDF_DIFF_ALG(xpp->flags) != XDF_HISTOGRAM_DIFF)) {
 		if (!XDL_ALLOC_ARRAY(xdf->rindex, xdf->nrec + 1))
 			goto abort;
-		if (!XDL_ALLOC_ARRAY(xdf->ha, xdf->nrec + 1))
-			goto abort;
 	}
 
 	xdf->rchg += 1;
@@ -300,9 +296,7 @@ static int xdl_cleanup_records(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xd
 	     i <= xdf1->dend; i++, recs++) {
 		if (dis1[i] == 1 ||
 		    (dis1[i] == 2 && !xdl_clean_mmatch(dis1, i, xdf1->dstart, xdf1->dend))) {
-			xdf1->rindex[nreff] = i;
-			xdf1->ha[nreff] = (*recs)->ha;
-			nreff++;
+			xdf1->rindex[nreff++] = i;
 		} else
 			xdf1->rchg[i] = 1;
 	}
@@ -312,9 +306,7 @@ static int xdl_cleanup_records(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xd
 	     i <= xdf2->dend; i++, recs++) {
 		if (dis2[i] == 1 ||
 		    (dis2[i] == 2 && !xdl_clean_mmatch(dis2, i, xdf2->dstart, xdf2->dend))) {
-			xdf2->rindex[nreff] = i;
-			xdf2->ha[nreff] = (*recs)->ha;
-			nreff++;
+			xdf2->rindex[nreff++] = i;
 		} else
 			xdf2->rchg[i] = 1;
 	}
diff --git a/xdiff/xtypes.h b/xdiff/xtypes.h
index 8b8467360e..85848f1685 100644
--- a/xdiff/xtypes.h
+++ b/xdiff/xtypes.h
@@ -52,7 +52,6 @@ typedef struct s_xdfile {
 	char *rchg;
 	long *rindex;
 	long nreff;
-	unsigned long *ha;
 } xdfile_t;
 
 typedef struct s_xdfenv {

From 6d507bd41a6f57f802a93a134cca0949a3d4370a Mon Sep 17 00:00:00 2001
From: Ezekiel Newren <ezekielnewren@gmail.com>
Date: Fri, 26 Sep 2025 22:41:55 +0000
Subject: [PATCH 08/12] xdiff: delete fields ha, line, size in xdlclass_t in
 favor of an xrecord_t

The fields from xdlclass_t are aliases of xrecord_t:
xdlclass_t.line -> xrecord_t.ptr
xdlclass_t.size -> xrecord_t.size
xdlclass_t.ha   -> xrecord_t.ha

xdlclass_t carries a copy of the data in xrecord_t, but instead of
embedding xrecord_t it duplicates the individual fields. A future
commit will change the types used in xrecord_t so embed it in
xdlclass_t first, so we don't have to remember to change the types
here as well.

Best-viewed-with: --color-words
Helped-by: Phillip Wood <phillip.wood123@gmail.com>
Signed-off-by: Ezekiel Newren <ezekielnewren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 xdiff/xprepare.c | 14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

diff --git a/xdiff/xprepare.c b/xdiff/xprepare.c
index 22c44f0683..e6e2c0e1c0 100644
--- a/xdiff/xprepare.c
+++ b/xdiff/xprepare.c
@@ -32,9 +32,7 @@
 
 typedef struct s_xdlclass {
 	struct s_xdlclass *next;
-	unsigned long ha;
-	char const *line;
-	long size;
+	xrecord_t rec;
 	long idx;
 	long len1, len2;
 } xdlclass_t;
@@ -93,14 +91,12 @@ static void xdl_free_classifier(xdlclassifier_t *cf) {
 
 static int xdl_classify_record(unsigned int pass, xdlclassifier_t *cf, xrecord_t *rec) {
 	long hi;
-	char const *line;
 	xdlclass_t *rcrec;
 
-	line = rec->ptr;
 	hi = (long) XDL_HASHLONG(rec->ha, cf->hbits);
 	for (rcrec = cf->rchash[hi]; rcrec; rcrec = rcrec->next)
-		if (rcrec->ha == rec->ha &&
-				xdl_recmatch(rcrec->line, rcrec->size,
+		if (rcrec->rec.ha == rec->ha &&
+				xdl_recmatch(rcrec->rec.ptr, rcrec->rec.size,
 					rec->ptr, rec->size, cf->flags))
 			break;
 
@@ -113,9 +109,7 @@ static int xdl_classify_record(unsigned int pass, xdlclassifier_t *cf, xrecord_t
 		if (XDL_ALLOC_GROW(cf->rcrecs, cf->count, cf->alloc))
 				return -1;
 		cf->rcrecs[rcrec->idx] = rcrec;
-		rcrec->line = line;
-		rcrec->size = rec->size;
-		rcrec->ha = rec->ha;
+		rcrec->rec = *rec;
 		rcrec->len1 = rcrec->len2 = 0;
 		rcrec->next = cf->rchash[hi];
 		cf->rchash[hi] = rcrec;

From d43d591252cfac10433aac01cc3d9d906c2f72c3 Mon Sep 17 00:00:00 2001
From: Ezekiel Newren <ezekielnewren@gmail.com>
Date: Fri, 26 Sep 2025 22:41:56 +0000
Subject: [PATCH 09/12] xdiff: delete chastore from xdfile_t
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

xdfile_t currently uses chastore_t which is an arena allocator. I
think that xrecord_t used to be a linked list and recs didn't exist
originally. When recs was added I think they forgot to remove
xdfile_t.next, but was overlooked. This dual data structure setup
makes the code somewhat confusing.

Additionally the C type chastore_t isn't FFI friendly, and provides
little to no performance benefit over using realloc to grow an array.

Performance impact of deleting fields from xdfile_t:
Deleting ha is about 5% slower.
Deleting cha is about 5% faster.

Delete ha, but keep cha
  time hyperfine --warmup 3 -L exe build_v2.51.0/git,build_delete_ha/git '{exe} log --oneline --shortstat --diff-algorithm=myers -3000 v2.39.1 >/dev/null'
  Benchmark 1: build_v2.51.0/git log --oneline --shortstat --diff-algorithm=myers -3000 v2.39.1 >/dev/null
    Time (mean ± σ):      1.269 s ±  0.017 s    [User: 1.135 s, System: 0.128 s]
    Range (min … max):    1.249 s …  1.286 s    10 runs

  Benchmark 2: build_delete_ha/git log --oneline --shortstat --diff-algorithm=myers -3000 v2.39.1 >/dev/null
    Time (mean ± σ):      1.339 s ±  0.017 s    [User: 1.234 s, System: 0.099 s]
    Range (min … max):    1.320 s …  1.358 s    10 runs

  Summary
    build_v2.51.0/git log --oneline --shortstat --diff-algorithm=myers -3000 v2.39.1 >/dev/null ran
      1.06 ± 0.02 times faster than build_delete_ha/git log --oneline --shortstat --diff-algorithm=myers -3000 v2.39.1 >/dev/null

Delete cha, but keep ha
  time hyperfine --warmup 3 -L exe build_v2.51.0/git,build_delete_chastore/git '{exe} log --oneline --shortstat --diff-algorithm=myers -3000 v2.39.1 >/dev/null'
  Benchmark 1: build_v2.51.0/git log --oneline --shortstat --diff-algorithm=myers -3000 v2.39.1 >/dev/null
    Time (mean ± σ):      1.290 s ±  0.001 s    [User: 1.154 s, System: 0.130 s]
    Range (min … max):    1.288 s …  1.292 s    10 runs

  Benchmark 2: build_delete_chastore/git log --oneline --shortstat --diff-algorithm=myers -3000 v2.39.1 >/dev/null
    Time (mean ± σ):      1.232 s ±  0.017 s    [User: 1.105 s, System: 0.121 s]
    Range (min … max):    1.205 s …  1.249 s    10 runs

  Summary
    build_delete_chastore/git log --oneline --shortstat --diff-algorithm=myers -3000 v2.39.1 >/dev/null ran
      1.05 ± 0.01 times faster than build_v2.51.0/git log --oneline --shortstat --diff-algorithm=myers -3000 v2.39.1 >/dev/null

Delete ha AND chastore
  time hyperfine --warmup 3 -L exe build_v2.51.0/git,build_delete_ha_and_chastore/git '{exe} log --oneline --shortstat --diff-algorithm=myers -3000 v2.39.1 >/dev/null'
  Benchmark 1: build_v2.51.0/git log --oneline --shortstat --diff-algorithm=myers -3000 v2.39.1 >/dev/null
    Time (mean ± σ):      1.291 s ±  0.002 s    [User: 1.156 s, System: 0.129 s]
    Range (min … max):    1.287 s …  1.295 s    10 runs

  Benchmark 2: build_delete_ha_and_chastore/git log --oneline --shortstat --diff-algorithm=myers -3000 v2.39.1 >/dev/null
    Time (mean ± σ):      1.306 s ±  0.001 s    [User: 1.195 s, System: 0.105 s]
    Range (min … max):    1.305 s …  1.308 s    10 runs

  Summary
    build_v2.51.0/git log --oneline --shortstat --diff-algorithm=myers -3000 v2.39.1 >/dev/null ran
      1.01 ± 0.00 times faster than build_delete_ha_and_chastore/git log --oneline --shortstat --diff-algorithm=myers -3000 v2.39.1 >/dev/null

Best-viewed-with: --color-words
Signed-off-by: Ezekiel Newren <ezekielnewren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 xdiff/xdiffi.c     | 24 ++++++++++----------
 xdiff/xemit.c      |  6 ++---
 xdiff/xhistogram.c |  2 +-
 xdiff/xmerge.c     | 56 +++++++++++++++++++++++-----------------------
 xdiff/xpatience.c  | 10 ++++-----
 xdiff/xprepare.c   | 19 ++++++----------
 xdiff/xtypes.h     |  3 +--
 xdiff/xutils.c     | 12 +++++-----
 8 files changed, 63 insertions(+), 69 deletions(-)

diff --git a/xdiff/xdiffi.c b/xdiff/xdiffi.c
index 11cd090b53..a66125d44a 100644
--- a/xdiff/xdiffi.c
+++ b/xdiff/xdiffi.c
@@ -24,7 +24,7 @@
 
 static unsigned long get_hash(xdfile_t *xdf, long index)
 {
-	return xdf->recs[xdf->rindex[index]]->ha;
+	return xdf->recs[xdf->rindex[index]].ha;
 }
 
 #define XDL_MAX_COST_MIN 256
@@ -489,13 +489,13 @@ static void measure_split(const xdfile_t *xdf, long split,
 		m->indent = -1;
 	} else {
 		m->end_of_file = 0;
-		m->indent = get_indent(xdf->recs[split]);
+		m->indent = get_indent(&xdf->recs[split]);
 	}
 
 	m->pre_blank = 0;
 	m->pre_indent = -1;
 	for (i = split - 1; i >= 0; i--) {
-		m->pre_indent = get_indent(xdf->recs[i]);
+		m->pre_indent = get_indent(&xdf->recs[i]);
 		if (m->pre_indent != -1)
 			break;
 		m->pre_blank += 1;
@@ -508,7 +508,7 @@ static void measure_split(const xdfile_t *xdf, long split,
 	m->post_blank = 0;
 	m->post_indent = -1;
 	for (i = split + 1; i < xdf->nrec; i++) {
-		m->post_indent = get_indent(xdf->recs[i]);
+		m->post_indent = get_indent(&xdf->recs[i]);
 		if (m->post_indent != -1)
 			break;
 		m->post_blank += 1;
@@ -752,7 +752,7 @@ static inline int group_previous(xdfile_t *xdf, struct xdlgroup *g)
 static int group_slide_down(xdfile_t *xdf, struct xdlgroup *g)
 {
 	if (g->end < xdf->nrec &&
-	    recs_match(xdf->recs[g->start], xdf->recs[g->end])) {
+	    recs_match(&xdf->recs[g->start], &xdf->recs[g->end])) {
 		xdf->rchg[g->start++] = 0;
 		xdf->rchg[g->end++] = 1;
 
@@ -773,7 +773,7 @@ static int group_slide_down(xdfile_t *xdf, struct xdlgroup *g)
 static int group_slide_up(xdfile_t *xdf, struct xdlgroup *g)
 {
 	if (g->start > 0 &&
-	    recs_match(xdf->recs[g->start - 1], xdf->recs[g->end - 1])) {
+	    recs_match(&xdf->recs[g->start - 1], &xdf->recs[g->end - 1])) {
 		xdf->rchg[--g->start] = 1;
 		xdf->rchg[--g->end] = 0;
 
@@ -988,16 +988,16 @@ static void xdl_mark_ignorable_lines(xdchange_t *xscr, xdfenv_t *xe, long flags)
 
 	for (xch = xscr; xch; xch = xch->next) {
 		int ignore = 1;
-		xrecord_t **rec;
+		xrecord_t *rec;
 		long i;
 
 		rec = &xe->xdf1.recs[xch->i1];
 		for (i = 0; i < xch->chg1 && ignore; i++)
-			ignore = xdl_blankline(rec[i]->ptr, rec[i]->size, flags);
+			ignore = xdl_blankline(rec[i].ptr, rec[i].size, flags);
 
 		rec = &xe->xdf2.recs[xch->i2];
 		for (i = 0; i < xch->chg2 && ignore; i++)
-			ignore = xdl_blankline(rec[i]->ptr, rec[i]->size, flags);
+			ignore = xdl_blankline(rec[i].ptr, rec[i].size, flags);
 
 		xch->ignore = ignore;
 	}
@@ -1021,7 +1021,7 @@ static void xdl_mark_ignorable_regex(xdchange_t *xscr, const xdfenv_t *xe,
 	xdchange_t *xch;
 
 	for (xch = xscr; xch; xch = xch->next) {
-		xrecord_t **rec;
+		xrecord_t *rec;
 		int ignore = 1;
 		long i;
 
@@ -1033,11 +1033,11 @@ static void xdl_mark_ignorable_regex(xdchange_t *xscr, const xdfenv_t *xe,
 
 		rec = &xe->xdf1.recs[xch->i1];
 		for (i = 0; i < xch->chg1 && ignore; i++)
-			ignore = record_matches_regex(rec[i], xpp);
+			ignore = record_matches_regex(&rec[i], xpp);
 
 		rec = &xe->xdf2.recs[xch->i2];
 		for (i = 0; i < xch->chg2 && ignore; i++)
-			ignore = record_matches_regex(rec[i], xpp);
+			ignore = record_matches_regex(&rec[i], xpp);
 
 		xch->ignore = ignore;
 	}
diff --git a/xdiff/xemit.c b/xdiff/xemit.c
index 2161ac3cd0..b2f1f30cd3 100644
--- a/xdiff/xemit.c
+++ b/xdiff/xemit.c
@@ -25,7 +25,7 @@
 
 static int xdl_emit_record(xdfile_t *xdf, long ri, char const *pre, xdemitcb_t *ecb)
 {
-	xrecord_t *rec = xdf->recs[ri];
+	xrecord_t *rec = &xdf->recs[ri];
 
 	if (xdl_emit_diffrec(rec->ptr, rec->size, pre, strlen(pre), ecb) < 0)
 		return -1;
@@ -110,7 +110,7 @@ static long def_ff(const char *rec, long len, char *buf, long sz)
 static long match_func_rec(xdfile_t *xdf, xdemitconf_t const *xecfg, long ri,
 			   char *buf, long sz)
 {
-	xrecord_t *rec = xdf->recs[ri];
+	xrecord_t *rec = &xdf->recs[ri];
 
 	if (!xecfg->find_func)
 		return def_ff(rec->ptr, rec->size, buf, sz);
@@ -150,7 +150,7 @@ static long get_func_line(xdfenv_t *xe, xdemitconf_t const *xecfg,
 
 static int is_empty_rec(xdfile_t *xdf, long ri)
 {
-	xrecord_t *rec = xdf->recs[ri];
+	xrecord_t *rec = &xdf->recs[ri];
 	long i = 0;
 
 	for (; i < rec->size && XDL_ISSPACE(rec->ptr[i]); i++);
diff --git a/xdiff/xhistogram.c b/xdiff/xhistogram.c
index 040d81e0bc..4d857e8ae2 100644
--- a/xdiff/xhistogram.c
+++ b/xdiff/xhistogram.c
@@ -86,7 +86,7 @@ struct region {
 	((LINE_MAP(index, ptr))->cnt)
 
 #define REC(env, s, l) \
-	(env->xdf##s.recs[l - 1])
+	(&env->xdf##s.recs[l - 1])
 
 static int cmp_recs(xrecord_t *r1, xrecord_t *r2)
 {
diff --git a/xdiff/xmerge.c b/xdiff/xmerge.c
index af40c88a5b..fd600cbb5d 100644
--- a/xdiff/xmerge.c
+++ b/xdiff/xmerge.c
@@ -97,12 +97,12 @@ static int xdl_merge_cmp_lines(xdfenv_t *xe1, int i1, xdfenv_t *xe2, int i2,
 		int line_count, long flags)
 {
 	int i;
-	xrecord_t **rec1 = xe1->xdf2.recs + i1;
-	xrecord_t **rec2 = xe2->xdf2.recs + i2;
+	xrecord_t *rec1 = xe1->xdf2.recs + i1;
+	xrecord_t *rec2 = xe2->xdf2.recs + i2;
 
 	for (i = 0; i < line_count; i++) {
-		int result = xdl_recmatch(rec1[i]->ptr, rec1[i]->size,
-			rec2[i]->ptr, rec2[i]->size, flags);
+		int result = xdl_recmatch(rec1[i].ptr, rec1[i].size,
+			rec2[i].ptr, rec2[i].size, flags);
 		if (!result)
 			return -1;
 	}
@@ -111,7 +111,7 @@ static int xdl_merge_cmp_lines(xdfenv_t *xe1, int i1, xdfenv_t *xe2, int i2,
 
 static int xdl_recs_copy_0(int use_orig, xdfenv_t *xe, int i, int count, int needs_cr, int add_nl, char *dest)
 {
-	xrecord_t **recs;
+	xrecord_t *recs;
 	int size = 0;
 
 	recs = (use_orig ? xe->xdf1.recs : xe->xdf2.recs) + i;
@@ -119,12 +119,12 @@ static int xdl_recs_copy_0(int use_orig, xdfenv_t *xe, int i, int count, int nee
 	if (count < 1)
 		return 0;
 
-	for (i = 0; i < count; size += recs[i++]->size)
+	for (i = 0; i < count; size += recs[i++].size)
 		if (dest)
-			memcpy(dest + size, recs[i]->ptr, recs[i]->size);
+			memcpy(dest + size, recs[i].ptr, recs[i].size);
 	if (add_nl) {
-		i = recs[count - 1]->size;
-		if (i == 0 || recs[count - 1]->ptr[i - 1] != '\n') {
+		i = recs[count - 1].size;
+		if (i == 0 || recs[count - 1].ptr[i - 1] != '\n') {
 			if (needs_cr) {
 				if (dest)
 					dest[size] = '\r';
@@ -160,22 +160,22 @@ static int is_eol_crlf(xdfile_t *file, int i)
 
 	if (i < file->nrec - 1)
 		/* All lines before the last *must* end in LF */
-		return (size = file->recs[i]->size) > 1 &&
-			file->recs[i]->ptr[size - 2] == '\r';
+		return (size = file->recs[i].size) > 1 &&
+			file->recs[i].ptr[size - 2] == '\r';
 	if (!file->nrec)
 		/* Cannot determine eol style from empty file */
 		return -1;
-	if ((size = file->recs[i]->size) &&
-			file->recs[i]->ptr[size - 1] == '\n')
+	if ((size = file->recs[i].size) &&
+			file->recs[i].ptr[size - 1] == '\n')
 		/* Last line; ends in LF; Is it CR/LF? */
 		return size > 1 &&
-			file->recs[i]->ptr[size - 2] == '\r';
+			file->recs[i].ptr[size - 2] == '\r';
 	if (!i)
 		/* The only line has no eol */
 		return -1;
 	/* Determine eol from second-to-last line */
-	return (size = file->recs[i - 1]->size) > 1 &&
-		file->recs[i - 1]->ptr[size - 2] == '\r';
+	return (size = file->recs[i - 1].size) > 1 &&
+		file->recs[i - 1].ptr[size - 2] == '\r';
 }
 
 static int is_cr_needed(xdfenv_t *xe1, xdfenv_t *xe2, xdmerge_t *m)
@@ -334,22 +334,22 @@ static int recmatch(xrecord_t *rec1, xrecord_t *rec2, unsigned long flags)
 static void xdl_refine_zdiff3_conflicts(xdfenv_t *xe1, xdfenv_t *xe2, xdmerge_t *m,
 		xpparam_t const *xpp)
 {
-	xrecord_t **rec1 = xe1->xdf2.recs, **rec2 = xe2->xdf2.recs;
+	xrecord_t *rec1 = xe1->xdf2.recs, *rec2 = xe2->xdf2.recs;
 	for (; m; m = m->next) {
 		/* let's handle just the conflicts */
 		if (m->mode)
 			continue;
 
 		while(m->chg1 && m->chg2 &&
-		      recmatch(rec1[m->i1], rec2[m->i2], xpp->flags)) {
+		      recmatch(&rec1[m->i1], &rec2[m->i2], xpp->flags)) {
 			m->chg1--;
 			m->chg2--;
 			m->i1++;
 			m->i2++;
 		}
 		while (m->chg1 && m->chg2 &&
-		       recmatch(rec1[m->i1 + m->chg1 - 1],
-				rec2[m->i2 + m->chg2 - 1], xpp->flags)) {
+		       recmatch(&rec1[m->i1 + m->chg1 - 1],
+				&rec2[m->i2 + m->chg2 - 1], xpp->flags)) {
 			m->chg1--;
 			m->chg2--;
 		}
@@ -381,12 +381,12 @@ static int xdl_refine_conflicts(xdfenv_t *xe1, xdfenv_t *xe2, xdmerge_t *m,
 		 * This probably does not work outside git, since
 		 * we have a very simple mmfile structure.
 		 */
-		t1.ptr = (char *)xe1->xdf2.recs[m->i1]->ptr;
-		t1.size = xe1->xdf2.recs[m->i1 + m->chg1 - 1]->ptr
-			+ xe1->xdf2.recs[m->i1 + m->chg1 - 1]->size - t1.ptr;
-		t2.ptr = (char *)xe2->xdf2.recs[m->i2]->ptr;
-		t2.size = xe2->xdf2.recs[m->i2 + m->chg2 - 1]->ptr
-			+ xe2->xdf2.recs[m->i2 + m->chg2 - 1]->size - t2.ptr;
+		t1.ptr = (char *)xe1->xdf2.recs[m->i1].ptr;
+		t1.size = xe1->xdf2.recs[m->i1 + m->chg1 - 1].ptr
+			+ xe1->xdf2.recs[m->i1 + m->chg1 - 1].size - t1.ptr;
+		t2.ptr = (char *)xe2->xdf2.recs[m->i2].ptr;
+		t2.size = xe2->xdf2.recs[m->i2 + m->chg2 - 1].ptr
+			+ xe2->xdf2.recs[m->i2 + m->chg2 - 1].size - t2.ptr;
 		if (xdl_do_diff(&t1, &t2, xpp, &xe) < 0)
 			return -1;
 		if (xdl_change_compact(&xe.xdf1, &xe.xdf2, xpp->flags) < 0 ||
@@ -440,8 +440,8 @@ static int line_contains_alnum(const char *ptr, long size)
 static int lines_contain_alnum(xdfenv_t *xe, int i, int chg)
 {
 	for (; chg; chg--, i++)
-		if (line_contains_alnum(xe->xdf2.recs[i]->ptr,
-				xe->xdf2.recs[i]->size))
+		if (line_contains_alnum(xe->xdf2.recs[i].ptr,
+				xe->xdf2.recs[i].size))
 			return 1;
 	return 0;
 }
diff --git a/xdiff/xpatience.c b/xdiff/xpatience.c
index 77dc411d19..bf69a58527 100644
--- a/xdiff/xpatience.c
+++ b/xdiff/xpatience.c
@@ -88,9 +88,9 @@ static int is_anchor(xpparam_t const *xpp, const char *line)
 static void insert_record(xpparam_t const *xpp, int line, struct hashmap *map,
 			  int pass)
 {
-	xrecord_t **records = pass == 1 ?
+	xrecord_t *records = pass == 1 ?
 		map->env->xdf1.recs : map->env->xdf2.recs;
-	xrecord_t *record = records[line - 1];
+	xrecord_t *record = &records[line - 1];
 	/*
 	 * After xdl_prepare_env() (or more precisely, due to
 	 * xdl_classify_record()), the "ha" member of the records (AKA lines)
@@ -121,7 +121,7 @@ static void insert_record(xpparam_t const *xpp, int line, struct hashmap *map,
 		return;
 	map->entries[index].line1 = line;
 	map->entries[index].hash = record->ha;
-	map->entries[index].anchor = is_anchor(xpp, map->env->xdf1.recs[line - 1]->ptr);
+	map->entries[index].anchor = is_anchor(xpp, map->env->xdf1.recs[line - 1].ptr);
 	if (!map->first)
 		map->first = map->entries + index;
 	if (map->last) {
@@ -246,8 +246,8 @@ static int find_longest_common_sequence(struct hashmap *map, struct entry **res)
 
 static int match(struct hashmap *map, int line1, int line2)
 {
-	xrecord_t *record1 = map->env->xdf1.recs[line1 - 1];
-	xrecord_t *record2 = map->env->xdf2.recs[line2 - 1];
+	xrecord_t *record1 = &map->env->xdf1.recs[line1 - 1];
+	xrecord_t *record2 = &map->env->xdf2.recs[line2 - 1];
 	return record1->ha == record2->ha;
 }
 
diff --git a/xdiff/xprepare.c b/xdiff/xprepare.c
index e6e2c0e1c0..27c5a4d636 100644
--- a/xdiff/xprepare.c
+++ b/xdiff/xprepare.c
@@ -128,7 +128,6 @@ static void xdl_free_ctx(xdfile_t *xdf)
 	xdl_free(xdf->rindex);
 	xdl_free(xdf->rchg - 1);
 	xdl_free(xdf->recs);
-	xdl_cha_free(&xdf->rcha);
 }
 
 
@@ -143,8 +142,6 @@ static int xdl_prepare_ctx(unsigned int pass, mmfile_t *mf, long narec, xpparam_
 	xdf->rchg = NULL;
 	xdf->recs = NULL;
 
-	if (xdl_cha_init(&xdf->rcha, sizeof(xrecord_t), narec / 4 + 1) < 0)
-		goto abort;
 	if (!XDL_ALLOC_ARRAY(xdf->recs, narec))
 		goto abort;
 
@@ -155,12 +152,10 @@ static int xdl_prepare_ctx(unsigned int pass, mmfile_t *mf, long narec, xpparam_
 			hav = xdl_hash_record(&cur, top, xpp->flags);
 			if (XDL_ALLOC_GROW(xdf->recs, xdf->nrec + 1, narec))
 				goto abort;
-			if (!(crec = xdl_cha_alloc(&xdf->rcha)))
-				goto abort;
+			crec = &xdf->recs[xdf->nrec++];
 			crec->ptr = prev;
 			crec->size = (long) (cur - prev);
 			crec->ha = hav;
-			xdf->recs[xdf->nrec++] = crec;
 			if (xdl_classify_record(pass, cf, crec) < 0)
 				goto abort;
 		}
@@ -260,7 +255,7 @@ static int xdl_clean_mmatch(char const *dis, long i, long s, long e) {
  */
 static int xdl_cleanup_records(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xdf2) {
 	long i, nm, nreff, mlim;
-	xrecord_t **recs;
+	xrecord_t *recs;
 	xdlclass_t *rcrec;
 	char *dis, *dis1, *dis2;
 	int need_min = !!(cf->flags & XDF_NEED_MINIMAL);
@@ -273,7 +268,7 @@ static int xdl_cleanup_records(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xd
 	if ((mlim = xdl_bogosqrt(xdf1->nrec)) > XDL_MAX_EQLIMIT)
 		mlim = XDL_MAX_EQLIMIT;
 	for (i = xdf1->dstart, recs = &xdf1->recs[xdf1->dstart]; i <= xdf1->dend; i++, recs++) {
-		rcrec = cf->rcrecs[(*recs)->ha];
+		rcrec = cf->rcrecs[recs->ha];
 		nm = rcrec ? rcrec->len2 : 0;
 		dis1[i] = (nm == 0) ? 0: (nm >= mlim && !need_min) ? 2: 1;
 	}
@@ -281,7 +276,7 @@ static int xdl_cleanup_records(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xd
 	if ((mlim = xdl_bogosqrt(xdf2->nrec)) > XDL_MAX_EQLIMIT)
 		mlim = XDL_MAX_EQLIMIT;
 	for (i = xdf2->dstart, recs = &xdf2->recs[xdf2->dstart]; i <= xdf2->dend; i++, recs++) {
-		rcrec = cf->rcrecs[(*recs)->ha];
+		rcrec = cf->rcrecs[recs->ha];
 		nm = rcrec ? rcrec->len1 : 0;
 		dis2[i] = (nm == 0) ? 0: (nm >= mlim && !need_min) ? 2: 1;
 	}
@@ -317,13 +312,13 @@ static int xdl_cleanup_records(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xd
  */
 static int xdl_trim_ends(xdfile_t *xdf1, xdfile_t *xdf2) {
 	long i, lim;
-	xrecord_t **recs1, **recs2;
+	xrecord_t *recs1, *recs2;
 
 	recs1 = xdf1->recs;
 	recs2 = xdf2->recs;
 	for (i = 0, lim = XDL_MIN(xdf1->nrec, xdf2->nrec); i < lim;
 	     i++, recs1++, recs2++)
-		if ((*recs1)->ha != (*recs2)->ha)
+		if (recs1->ha != recs2->ha)
 			break;
 
 	xdf1->dstart = xdf2->dstart = i;
@@ -331,7 +326,7 @@ static int xdl_trim_ends(xdfile_t *xdf1, xdfile_t *xdf2) {
 	recs1 = xdf1->recs + xdf1->nrec - 1;
 	recs2 = xdf2->recs + xdf2->nrec - 1;
 	for (lim -= i, i = 0; i < lim; i++, recs1--, recs2--)
-		if ((*recs1)->ha != (*recs2)->ha)
+		if (recs1->ha != recs2->ha)
 			break;
 
 	xdf1->dend = xdf1->nrec - i - 1;
diff --git a/xdiff/xtypes.h b/xdiff/xtypes.h
index 85848f1685..3d26cbf1ec 100644
--- a/xdiff/xtypes.h
+++ b/xdiff/xtypes.h
@@ -45,10 +45,9 @@ typedef struct s_xrecord {
 } xrecord_t;
 
 typedef struct s_xdfile {
-	chastore_t rcha;
+	xrecord_t *recs;
 	long nrec;
 	long dstart, dend;
-	xrecord_t **recs;
 	char *rchg;
 	long *rindex;
 	long nreff;
diff --git a/xdiff/xutils.c b/xdiff/xutils.c
index 444a108f87..332982b509 100644
--- a/xdiff/xutils.c
+++ b/xdiff/xutils.c
@@ -416,12 +416,12 @@ int xdl_fall_back_diff(xdfenv_t *diff_env, xpparam_t const *xpp,
 	mmfile_t subfile1, subfile2;
 	xdfenv_t env;
 
-	subfile1.ptr = (char *)diff_env->xdf1.recs[line1 - 1]->ptr;
-	subfile1.size = diff_env->xdf1.recs[line1 + count1 - 2]->ptr +
-		diff_env->xdf1.recs[line1 + count1 - 2]->size - subfile1.ptr;
-	subfile2.ptr = (char *)diff_env->xdf2.recs[line2 - 1]->ptr;
-	subfile2.size = diff_env->xdf2.recs[line2 + count2 - 2]->ptr +
-		diff_env->xdf2.recs[line2 + count2 - 2]->size - subfile2.ptr;
+	subfile1.ptr = (char *)diff_env->xdf1.recs[line1 - 1].ptr;
+	subfile1.size = diff_env->xdf1.recs[line1 + count1 - 2].ptr +
+		diff_env->xdf1.recs[line1 + count1 - 2].size - subfile1.ptr;
+	subfile2.ptr = (char *)diff_env->xdf2.recs[line2 - 1].ptr;
+	subfile2.size = diff_env->xdf2.recs[line2 + count2 - 2].ptr +
+		diff_env->xdf2.recs[line2 + count2 - 2].size - subfile2.ptr;
 	if (xdl_do_diff(&subfile1, &subfile2, xpp, &env) < 0)
 		return -1;
 

From b7de64a6d6f58953a0c1dc7ff34f7080b3e38b37 Mon Sep 17 00:00:00 2001
From: Ezekiel Newren <ezekielnewren@gmail.com>
Date: Fri, 26 Sep 2025 22:41:57 +0000
Subject: [PATCH 10/12] xdiff: rename rchg -> changed in xdfile_t

The field rchg (now 'changed') declares if a line in a file is changed
or not. A later commit will change it's type from 'char' to 'bool'
to make its purpose even more clear.

Best-viewed-with: --color-words
Signed-off-by: Ezekiel Newren <ezekielnewren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 xdiff/xdiffi.c     | 30 +++++++++++++++---------------
 xdiff/xhistogram.c |  8 ++++----
 xdiff/xpatience.c  |  8 ++++----
 xdiff/xprepare.c   | 12 ++++++------
 xdiff/xtypes.h     |  2 +-
 xdiff/xutils.c     |  4 ++--
 6 files changed, 32 insertions(+), 32 deletions(-)

diff --git a/xdiff/xdiffi.c b/xdiff/xdiffi.c
index a66125d44a..bd5b31c664 100644
--- a/xdiff/xdiffi.c
+++ b/xdiff/xdiffi.c
@@ -278,10 +278,10 @@ int xdl_recs_cmp(xdfile_t *xdf1, long off1, long lim1,
 	 */
 	if (off1 == lim1) {
 		for (; off2 < lim2; off2++)
-			xdf2->rchg[xdf2->rindex[off2]] = 1;
+			xdf2->changed[xdf2->rindex[off2]] = 1;
 	} else if (off2 == lim2) {
 		for (; off1 < lim1; off1++)
-			xdf1->rchg[xdf1->rindex[off1]] = 1;
+			xdf1->changed[xdf1->rindex[off1]] = 1;
 	} else {
 		xdpsplit_t spl;
 		spl.i1 = spl.i2 = 0;
@@ -708,7 +708,7 @@ struct xdlgroup {
 static void group_init(xdfile_t *xdf, struct xdlgroup *g)
 {
 	g->start = g->end = 0;
-	while (xdf->rchg[g->end])
+	while (xdf->changed[g->end])
 		g->end++;
 }
 
@@ -722,7 +722,7 @@ static inline int group_next(xdfile_t *xdf, struct xdlgroup *g)
 		return -1;
 
 	g->start = g->end + 1;
-	for (g->end = g->start; xdf->rchg[g->end]; g->end++)
+	for (g->end = g->start; xdf->changed[g->end]; g->end++)
 		;
 
 	return 0;
@@ -738,7 +738,7 @@ static inline int group_previous(xdfile_t *xdf, struct xdlgroup *g)
 		return -1;
 
 	g->end = g->start - 1;
-	for (g->start = g->end; xdf->rchg[g->start - 1]; g->start--)
+	for (g->start = g->end; xdf->changed[g->start - 1]; g->start--)
 		;
 
 	return 0;
@@ -753,10 +753,10 @@ static int group_slide_down(xdfile_t *xdf, struct xdlgroup *g)
 {
 	if (g->end < xdf->nrec &&
 	    recs_match(&xdf->recs[g->start], &xdf->recs[g->end])) {
-		xdf->rchg[g->start++] = 0;
-		xdf->rchg[g->end++] = 1;
+		xdf->changed[g->start++] = 0;
+		xdf->changed[g->end++] = 1;
 
-		while (xdf->rchg[g->end])
+		while (xdf->changed[g->end])
 			g->end++;
 
 		return 0;
@@ -774,10 +774,10 @@ static int group_slide_up(xdfile_t *xdf, struct xdlgroup *g)
 {
 	if (g->start > 0 &&
 	    recs_match(&xdf->recs[g->start - 1], &xdf->recs[g->end - 1])) {
-		xdf->rchg[--g->start] = 1;
-		xdf->rchg[--g->end] = 0;
+		xdf->changed[--g->start] = 1;
+		xdf->changed[--g->end] = 0;
 
-		while (xdf->rchg[g->start - 1])
+		while (xdf->changed[g->start - 1])
 			g->start--;
 
 		return 0;
@@ -932,16 +932,16 @@ int xdl_change_compact(xdfile_t *xdf, xdfile_t *xdfo, long flags) {
 
 int xdl_build_script(xdfenv_t *xe, xdchange_t **xscr) {
 	xdchange_t *cscr = NULL, *xch;
-	char *rchg1 = xe->xdf1.rchg, *rchg2 = xe->xdf2.rchg;
+	char *changed1 = xe->xdf1.changed, *changed2 = xe->xdf2.changed;
 	long i1, i2, l1, l2;
 
 	/*
 	 * Trivial. Collects "groups" of changes and creates an edit script.
 	 */
 	for (i1 = xe->xdf1.nrec, i2 = xe->xdf2.nrec; i1 >= 0 || i2 >= 0; i1--, i2--)
-		if (rchg1[i1 - 1] || rchg2[i2 - 1]) {
-			for (l1 = i1; rchg1[i1 - 1]; i1--);
-			for (l2 = i2; rchg2[i2 - 1]; i2--);
+		if (changed1[i1 - 1] || changed2[i2 - 1]) {
+			for (l1 = i1; changed1[i1 - 1]; i1--);
+			for (l2 = i2; changed2[i2 - 1]; i2--);
 
 			if (!(xch = xdl_add_change(cscr, i1, i2, l1 - i1, l2 - i2))) {
 				xdl_free_script(cscr);
diff --git a/xdiff/xhistogram.c b/xdiff/xhistogram.c
index 4d857e8ae2..15ca15f6b0 100644
--- a/xdiff/xhistogram.c
+++ b/xdiff/xhistogram.c
@@ -318,11 +318,11 @@ redo:
 
 	if (!count1) {
 		while(count2--)
-			env->xdf2.rchg[line2++ - 1] = 1;
+			env->xdf2.changed[line2++ - 1] = 1;
 		return 0;
 	} else if (!count2) {
 		while(count1--)
-			env->xdf1.rchg[line1++ - 1] = 1;
+			env->xdf1.changed[line1++ - 1] = 1;
 		return 0;
 	}
 
@@ -335,9 +335,9 @@ redo:
 	else {
 		if (lcs.begin1 == 0 && lcs.begin2 == 0) {
 			while (count1--)
-				env->xdf1.rchg[line1++ - 1] = 1;
+				env->xdf1.changed[line1++ - 1] = 1;
 			while (count2--)
-				env->xdf2.rchg[line2++ - 1] = 1;
+				env->xdf2.changed[line2++ - 1] = 1;
 			result = 0;
 		} else {
 			result = histogram_diff(xpp, env,
diff --git a/xdiff/xpatience.c b/xdiff/xpatience.c
index bf69a58527..14092ffb86 100644
--- a/xdiff/xpatience.c
+++ b/xdiff/xpatience.c
@@ -331,11 +331,11 @@ static int patience_diff(xpparam_t const *xpp, xdfenv_t *env,
 	/* trivial case: one side is empty */
 	if (!count1) {
 		while(count2--)
-			env->xdf2.rchg[line2++ - 1] = 1;
+			env->xdf2.changed[line2++ - 1] = 1;
 		return 0;
 	} else if (!count2) {
 		while(count1--)
-			env->xdf1.rchg[line1++ - 1] = 1;
+			env->xdf1.changed[line1++ - 1] = 1;
 		return 0;
 	}
 
@@ -347,9 +347,9 @@ static int patience_diff(xpparam_t const *xpp, xdfenv_t *env,
 	/* are there any matching lines at all? */
 	if (!map.has_matches) {
 		while(count1--)
-			env->xdf1.rchg[line1++ - 1] = 1;
+			env->xdf1.changed[line1++ - 1] = 1;
 		while(count2--)
-			env->xdf2.rchg[line2++ - 1] = 1;
+			env->xdf2.changed[line2++ - 1] = 1;
 		xdl_free(map.entries);
 		return 0;
 	}
diff --git a/xdiff/xprepare.c b/xdiff/xprepare.c
index 27c5a4d636..b9b19c36de 100644
--- a/xdiff/xprepare.c
+++ b/xdiff/xprepare.c
@@ -126,7 +126,7 @@ static int xdl_classify_record(unsigned int pass, xdlclassifier_t *cf, xrecord_t
 static void xdl_free_ctx(xdfile_t *xdf)
 {
 	xdl_free(xdf->rindex);
-	xdl_free(xdf->rchg - 1);
+	xdl_free(xdf->changed - 1);
 	xdl_free(xdf->recs);
 }
 
@@ -139,7 +139,7 @@ static int xdl_prepare_ctx(unsigned int pass, mmfile_t *mf, long narec, xpparam_
 	xrecord_t *crec;
 
 	xdf->rindex = NULL;
-	xdf->rchg = NULL;
+	xdf->changed = NULL;
 	xdf->recs = NULL;
 
 	if (!XDL_ALLOC_ARRAY(xdf->recs, narec))
@@ -161,7 +161,7 @@ static int xdl_prepare_ctx(unsigned int pass, mmfile_t *mf, long narec, xpparam_
 		}
 	}
 
-	if (!XDL_CALLOC_ARRAY(xdf->rchg, xdf->nrec + 2))
+	if (!XDL_CALLOC_ARRAY(xdf->changed, xdf->nrec + 2))
 		goto abort;
 
 	if ((XDF_DIFF_ALG(xpp->flags) != XDF_PATIENCE_DIFF) &&
@@ -170,7 +170,7 @@ static int xdl_prepare_ctx(unsigned int pass, mmfile_t *mf, long narec, xpparam_
 			goto abort;
 	}
 
-	xdf->rchg += 1;
+	xdf->changed += 1;
 	xdf->nreff = 0;
 	xdf->dstart = 0;
 	xdf->dend = xdf->nrec - 1;
@@ -287,7 +287,7 @@ static int xdl_cleanup_records(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xd
 		    (dis1[i] == 2 && !xdl_clean_mmatch(dis1, i, xdf1->dstart, xdf1->dend))) {
 			xdf1->rindex[nreff++] = i;
 		} else
-			xdf1->rchg[i] = 1;
+			xdf1->changed[i] = 1;
 	}
 	xdf1->nreff = nreff;
 
@@ -297,7 +297,7 @@ static int xdl_cleanup_records(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xd
 		    (dis2[i] == 2 && !xdl_clean_mmatch(dis2, i, xdf2->dstart, xdf2->dend))) {
 			xdf2->rindex[nreff++] = i;
 		} else
-			xdf2->rchg[i] = 1;
+			xdf2->changed[i] = 1;
 	}
 	xdf2->nreff = nreff;
 
diff --git a/xdiff/xtypes.h b/xdiff/xtypes.h
index 3d26cbf1ec..c4b5d2d8fa 100644
--- a/xdiff/xtypes.h
+++ b/xdiff/xtypes.h
@@ -48,7 +48,7 @@ typedef struct s_xdfile {
 	xrecord_t *recs;
 	long nrec;
 	long dstart, dend;
-	char *rchg;
+	char *changed;
 	long *rindex;
 	long nreff;
 } xdfile_t;
diff --git a/xdiff/xutils.c b/xdiff/xutils.c
index 332982b509..ed65c222e6 100644
--- a/xdiff/xutils.c
+++ b/xdiff/xutils.c
@@ -425,8 +425,8 @@ int xdl_fall_back_diff(xdfenv_t *diff_env, xpparam_t const *xpp,
 	if (xdl_do_diff(&subfile1, &subfile2, xpp, &env) < 0)
 		return -1;
 
-	memcpy(diff_env->xdf1.rchg + line1 - 1, env.xdf1.rchg, count1);
-	memcpy(diff_env->xdf2.rchg + line2 - 1, env.xdf2.rchg, count2);
+	memcpy(diff_env->xdf1.changed + line1 - 1, env.xdf1.changed, count1);
+	memcpy(diff_env->xdf2.changed + line2 - 1, env.xdf2.changed, count2);
 
 	xdl_free_env(&env);
 

From e385e1b7d2d7f531a0006131e7f1d974de351df5 Mon Sep 17 00:00:00 2001
From: Ezekiel Newren <ezekielnewren@gmail.com>
Date: Fri, 26 Sep 2025 22:41:58 +0000
Subject: [PATCH 11/12] xdiff: add macros DISCARD(0), KEEP(1), INVESTIGATE(2)
 in xprepare.c

This commit is refactor-only; no behavior is changed. A future commit
will use bool literals for changed[i].

The functions xdl_clean_mmatch() and xdl_cleanup_records() will be
cleaned up more in a future patch series. The changes to
xdl_cleanup_records(), in this patch, are just to make it clear why
`char rchg` is refactored to `bool changed`.

Rename dis* to action* and replace literal numericals with macros.
The old names came from when dis* (which I think was short for discard)
was treated like a boolean, but over time it grew into a ternary state
machine. The result was confusing because dis* and rchg* both used 0/1
values with different meanings.

The new names and macros make the states explicit. nm is short for
number of matches, and mlim is a heuristic limit:

  nm == 0       -> action[i] = DISCARD     -> changed[i] = true
  0 < nm < mlim -> action[i] = KEEP        -> changed[i] = false
  nm >= mlim    -> action[i] = INVESTIGATE -> changed[i] = xdl_clean_mmatch()

When need_min is true, only DISCARD and KEEP occur because the limit
is effectively infinite.

Best-viewed-with: --color-words
Signed-off-by: Ezekiel Newren <ezekielnewren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 xdiff/xprepare.c | 106 ++++++++++++++++++++++++++++++-----------------
 1 file changed, 69 insertions(+), 37 deletions(-)

diff --git a/xdiff/xprepare.c b/xdiff/xprepare.c
index b9b19c36de..55e3b50ce6 100644
--- a/xdiff/xprepare.c
+++ b/xdiff/xprepare.c
@@ -29,6 +29,9 @@
 #define XDL_GUESS_NLINES1 256
 #define XDL_GUESS_NLINES2 20
 
+#define DISCARD 0
+#define KEEP 1
+#define INVESTIGATE 2
 
 typedef struct s_xdlclass {
 	struct s_xdlclass *next;
@@ -190,15 +193,15 @@ void xdl_free_env(xdfenv_t *xe) {
 }
 
 
-static int xdl_clean_mmatch(char const *dis, long i, long s, long e) {
+static bool xdl_clean_mmatch(uint8_t const *action, long i, long s, long e) {
 	long r, rdis0, rpdis0, rdis1, rpdis1;
 
 	/*
-	 * Limits the window the is examined during the similar-lines
-	 * scan. The loops below stops when dis[i - r] == 1 (line that
-	 * has no match), but there are corner cases where the loop
-	 * proceed all the way to the extremities by causing huge
-	 * performance penalties in case of big files.
+	 * Limits the window that is examined during the similar-lines
+	 * scan. The loops below stops when action[i - r] == KEEP
+	 * (line that has no match), but there are corner cases where
+	 * the loop proceed all the way to the extremities by causing
+	 * huge performance penalties in case of big files.
 	 */
 	if (i - s > XDL_SIMSCAN_WINDOW)
 		s = i - XDL_SIMSCAN_WINDOW;
@@ -207,40 +210,47 @@ static int xdl_clean_mmatch(char const *dis, long i, long s, long e) {
 
 	/*
 	 * Scans the lines before 'i' to find a run of lines that either
-	 * have no match (dis[j] == 0) or have multiple matches (dis[j] > 1).
-	 * Note that we always call this function with dis[i] > 1, so the
-	 * current line (i) is already a multimatch line.
+	 * have no match (action[j] == DISCARD) or have multiple matches
+	 * (action[j] == INVESTIGATE). Note that we always call this
+	 * function with action[i] == INVESTIGATE, so the current line
+	 * (i) is already a multimatch line.
 	 */
 	for (r = 1, rdis0 = 0, rpdis0 = 1; (i - r) >= s; r++) {
-		if (!dis[i - r])
+		if (action[i - r] == DISCARD)
 			rdis0++;
-		else if (dis[i - r] == 2)
+		else if (action[i - r] == INVESTIGATE)
 			rpdis0++;
-		else
+		else if (action[i - r] == KEEP)
 			break;
+		else
+			BUG("Illegal value for action[i - r]");
 	}
 	/*
-	 * If the run before the line 'i' found only multimatch lines, we
-	 * return 0 and hence we don't make the current line (i) discarded.
-	 * We want to discard multimatch lines only when they appear in the
-	 * middle of runs with nomatch lines (dis[j] == 0).
+	 * If the run before the line 'i' found only multimatch lines,
+	 * we return false and hence we don't make the current line (i)
+	 * discarded. We want to discard multimatch lines only when
+	 * they appear in the middle of runs with nomatch lines
+	 * (action[j] == DISCARD).
 	 */
 	if (rdis0 == 0)
 		return 0;
 	for (r = 1, rdis1 = 0, rpdis1 = 1; (i + r) <= e; r++) {
-		if (!dis[i + r])
+		if (action[i + r] == DISCARD)
 			rdis1++;
-		else if (dis[i + r] == 2)
+		else if (action[i + r] == INVESTIGATE)
 			rpdis1++;
-		else
+		else if (action[i + r] == KEEP)
 			break;
+		else
+			BUG("Illegal value for action[i + r]");
 	}
 	/*
-	 * If the run after the line 'i' found only multimatch lines, we
-	 * return 0 and hence we don't make the current line (i) discarded.
+	 * If the run after the line 'i' found only multimatch lines,
+	 * we return false and hence we don't make the current line (i)
+	 * discarded.
 	 */
 	if (rdis1 == 0)
-		return 0;
+		return false;
 	rdis1 += rdis0;
 	rpdis1 += rpdis0;
 
@@ -251,26 +261,38 @@ static int xdl_clean_mmatch(char const *dis, long i, long s, long e) {
 /*
  * Try to reduce the problem complexity, discard records that have no
  * matches on the other file. Also, lines that have multiple matches
- * might be potentially discarded if they happear in a run of discardable.
+ * might be potentially discarded if they appear in a run of discardable.
  */
 static int xdl_cleanup_records(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xdf2) {
 	long i, nm, nreff, mlim;
 	xrecord_t *recs;
 	xdlclass_t *rcrec;
-	char *dis, *dis1, *dis2;
-	int need_min = !!(cf->flags & XDF_NEED_MINIMAL);
+	uint8_t *action1 = NULL, *action2 = NULL;
+	bool need_min = !!(cf->flags & XDF_NEED_MINIMAL);
+	int ret = 0;
 
-	if (!XDL_CALLOC_ARRAY(dis, xdf1->nrec + xdf2->nrec + 2))
-		return -1;
-	dis1 = dis;
-	dis2 = dis1 + xdf1->nrec + 1;
+	/*
+	 * Create temporary arrays that will help us decide if
+	 * changed[i] should remain 0 or become 1.
+	 */
+	if (!XDL_CALLOC_ARRAY(action1, xdf1->nrec + 1)) {
+		ret = -1;
+		goto cleanup;
+	}
+	if (!XDL_CALLOC_ARRAY(action2, xdf2->nrec + 1)) {
+		ret = -1;
+		goto cleanup;
+	}
 
+	/*
+	 * Initialize temporary arrays with DISCARD, KEEP, or INVESTIGATE.
+	 */
 	if ((mlim = xdl_bogosqrt(xdf1->nrec)) > XDL_MAX_EQLIMIT)
 		mlim = XDL_MAX_EQLIMIT;
 	for (i = xdf1->dstart, recs = &xdf1->recs[xdf1->dstart]; i <= xdf1->dend; i++, recs++) {
 		rcrec = cf->rcrecs[recs->ha];
 		nm = rcrec ? rcrec->len2 : 0;
-		dis1[i] = (nm == 0) ? 0: (nm >= mlim && !need_min) ? 2: 1;
+		action1[i] = (nm == 0) ? DISCARD: (nm >= mlim && !need_min) ? INVESTIGATE: KEEP;
 	}
 
 	if ((mlim = xdl_bogosqrt(xdf2->nrec)) > XDL_MAX_EQLIMIT)
@@ -278,32 +300,42 @@ static int xdl_cleanup_records(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xd
 	for (i = xdf2->dstart, recs = &xdf2->recs[xdf2->dstart]; i <= xdf2->dend; i++, recs++) {
 		rcrec = cf->rcrecs[recs->ha];
 		nm = rcrec ? rcrec->len1 : 0;
-		dis2[i] = (nm == 0) ? 0: (nm >= mlim && !need_min) ? 2: 1;
+		action2[i] = (nm == 0) ? DISCARD: (nm >= mlim && !need_min) ? INVESTIGATE: KEEP;
 	}
 
+	/*
+	 * Use temporary arrays to decide if changed[i] should remain
+	 * 0 or become 1.
+	 */
 	for (nreff = 0, i = xdf1->dstart, recs = &xdf1->recs[xdf1->dstart];
 	     i <= xdf1->dend; i++, recs++) {
-		if (dis1[i] == 1 ||
-		    (dis1[i] == 2 && !xdl_clean_mmatch(dis1, i, xdf1->dstart, xdf1->dend))) {
+		if (action1[i] == KEEP ||
+		    (action1[i] == INVESTIGATE && !xdl_clean_mmatch(action1, i, xdf1->dstart, xdf1->dend))) {
 			xdf1->rindex[nreff++] = i;
+			/* changed[i] remains 0, i.e. keep */
 		} else
 			xdf1->changed[i] = 1;
+			/* i.e. discard */
 	}
 	xdf1->nreff = nreff;
 
 	for (nreff = 0, i = xdf2->dstart, recs = &xdf2->recs[xdf2->dstart];
 	     i <= xdf2->dend; i++, recs++) {
-		if (dis2[i] == 1 ||
-		    (dis2[i] == 2 && !xdl_clean_mmatch(dis2, i, xdf2->dstart, xdf2->dend))) {
+		if (action2[i] == KEEP ||
+		    (action2[i] == INVESTIGATE && !xdl_clean_mmatch(action2, i, xdf2->dstart, xdf2->dend))) {
 			xdf2->rindex[nreff++] = i;
+			/* changed[i] remains 0, i.e. keep */
 		} else
 			xdf2->changed[i] = 1;
+			/* i.e. discard */
 	}
 	xdf2->nreff = nreff;
 
-	xdl_free(dis);
+cleanup:
+	xdl_free(action1);
+	xdl_free(action2);
 
-	return 0;
+	return ret;
 }
 
 

From 8b9c5d2e3a38b6e0c2278fe10fe2a4bf34496a9d Mon Sep 17 00:00:00 2001
From: Ezekiel Newren <ezekielnewren@gmail.com>
Date: Fri, 26 Sep 2025 22:41:59 +0000
Subject: [PATCH 12/12] xdiff: change type of xdfile_t.changed from char to
 bool

The only values possible for 'changed' is 1 and 0, which exactly maps
to a bool type. It might not look like this because action1 and action2
(which use to be dis1, and dis2) were also of type char and were
assigned numerical values within a few lines of 'changed' (what used to
be rchg).

Using DISCARD/KEEP/INVESTIGATE for action1[i]/action2[j], and true/false
for changed[k] makes it clear to future readers that these are
logically separate concepts.

Best-viewed-with: --color-words
Signed-off-by: Ezekiel Newren <ezekielnewren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 xdiff/xdiffi.c     | 14 +++++++-------
 xdiff/xhistogram.c |  8 ++++----
 xdiff/xpatience.c  |  8 ++++----
 xdiff/xprepare.c   | 12 ++++++------
 xdiff/xtypes.h     |  2 +-
 5 files changed, 22 insertions(+), 22 deletions(-)

diff --git a/xdiff/xdiffi.c b/xdiff/xdiffi.c
index bd5b31c664..6f3998ee54 100644
--- a/xdiff/xdiffi.c
+++ b/xdiff/xdiffi.c
@@ -278,10 +278,10 @@ int xdl_recs_cmp(xdfile_t *xdf1, long off1, long lim1,
 	 */
 	if (off1 == lim1) {
 		for (; off2 < lim2; off2++)
-			xdf2->changed[xdf2->rindex[off2]] = 1;
+			xdf2->changed[xdf2->rindex[off2]] = true;
 	} else if (off2 == lim2) {
 		for (; off1 < lim1; off1++)
-			xdf1->changed[xdf1->rindex[off1]] = 1;
+			xdf1->changed[xdf1->rindex[off1]] = true;
 	} else {
 		xdpsplit_t spl;
 		spl.i1 = spl.i2 = 0;
@@ -753,8 +753,8 @@ static int group_slide_down(xdfile_t *xdf, struct xdlgroup *g)
 {
 	if (g->end < xdf->nrec &&
 	    recs_match(&xdf->recs[g->start], &xdf->recs[g->end])) {
-		xdf->changed[g->start++] = 0;
-		xdf->changed[g->end++] = 1;
+		xdf->changed[g->start++] = false;
+		xdf->changed[g->end++] = true;
 
 		while (xdf->changed[g->end])
 			g->end++;
@@ -774,8 +774,8 @@ static int group_slide_up(xdfile_t *xdf, struct xdlgroup *g)
 {
 	if (g->start > 0 &&
 	    recs_match(&xdf->recs[g->start - 1], &xdf->recs[g->end - 1])) {
-		xdf->changed[--g->start] = 1;
-		xdf->changed[--g->end] = 0;
+		xdf->changed[--g->start] = true;
+		xdf->changed[--g->end] = false;
 
 		while (xdf->changed[g->start - 1])
 			g->start--;
@@ -932,7 +932,7 @@ int xdl_change_compact(xdfile_t *xdf, xdfile_t *xdfo, long flags) {
 
 int xdl_build_script(xdfenv_t *xe, xdchange_t **xscr) {
 	xdchange_t *cscr = NULL, *xch;
-	char *changed1 = xe->xdf1.changed, *changed2 = xe->xdf2.changed;
+	bool *changed1 = xe->xdf1.changed, *changed2 = xe->xdf2.changed;
 	long i1, i2, l1, l2;
 
 	/*
diff --git a/xdiff/xhistogram.c b/xdiff/xhistogram.c
index 15ca15f6b0..6dc450b1fe 100644
--- a/xdiff/xhistogram.c
+++ b/xdiff/xhistogram.c
@@ -318,11 +318,11 @@ redo:
 
 	if (!count1) {
 		while(count2--)
-			env->xdf2.changed[line2++ - 1] = 1;
+			env->xdf2.changed[line2++ - 1] = true;
 		return 0;
 	} else if (!count2) {
 		while(count1--)
-			env->xdf1.changed[line1++ - 1] = 1;
+			env->xdf1.changed[line1++ - 1] = true;
 		return 0;
 	}
 
@@ -335,9 +335,9 @@ redo:
 	else {
 		if (lcs.begin1 == 0 && lcs.begin2 == 0) {
 			while (count1--)
-				env->xdf1.changed[line1++ - 1] = 1;
+				env->xdf1.changed[line1++ - 1] = true;
 			while (count2--)
-				env->xdf2.changed[line2++ - 1] = 1;
+				env->xdf2.changed[line2++ - 1] = true;
 			result = 0;
 		} else {
 			result = histogram_diff(xpp, env,
diff --git a/xdiff/xpatience.c b/xdiff/xpatience.c
index 14092ffb86..669b653580 100644
--- a/xdiff/xpatience.c
+++ b/xdiff/xpatience.c
@@ -331,11 +331,11 @@ static int patience_diff(xpparam_t const *xpp, xdfenv_t *env,
 	/* trivial case: one side is empty */
 	if (!count1) {
 		while(count2--)
-			env->xdf2.changed[line2++ - 1] = 1;
+			env->xdf2.changed[line2++ - 1] = true;
 		return 0;
 	} else if (!count2) {
 		while(count1--)
-			env->xdf1.changed[line1++ - 1] = 1;
+			env->xdf1.changed[line1++ - 1] = true;
 		return 0;
 	}
 
@@ -347,9 +347,9 @@ static int patience_diff(xpparam_t const *xpp, xdfenv_t *env,
 	/* are there any matching lines at all? */
 	if (!map.has_matches) {
 		while(count1--)
-			env->xdf1.changed[line1++ - 1] = 1;
+			env->xdf1.changed[line1++ - 1] = true;
 		while(count2--)
-			env->xdf2.changed[line2++ - 1] = 1;
+			env->xdf2.changed[line2++ - 1] = true;
 		xdl_free(map.entries);
 		return 0;
 	}
diff --git a/xdiff/xprepare.c b/xdiff/xprepare.c
index 55e3b50ce6..192334f1b7 100644
--- a/xdiff/xprepare.c
+++ b/xdiff/xprepare.c
@@ -273,7 +273,7 @@ static int xdl_cleanup_records(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xd
 
 	/*
 	 * Create temporary arrays that will help us decide if
-	 * changed[i] should remain 0 or become 1.
+	 * changed[i] should remain false, or become true.
 	 */
 	if (!XDL_CALLOC_ARRAY(action1, xdf1->nrec + 1)) {
 		ret = -1;
@@ -305,16 +305,16 @@ static int xdl_cleanup_records(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xd
 
 	/*
 	 * Use temporary arrays to decide if changed[i] should remain
-	 * 0 or become 1.
+	 * false, or become true.
 	 */
 	for (nreff = 0, i = xdf1->dstart, recs = &xdf1->recs[xdf1->dstart];
 	     i <= xdf1->dend; i++, recs++) {
 		if (action1[i] == KEEP ||
 		    (action1[i] == INVESTIGATE && !xdl_clean_mmatch(action1, i, xdf1->dstart, xdf1->dend))) {
 			xdf1->rindex[nreff++] = i;
-			/* changed[i] remains 0, i.e. keep */
+			/* changed[i] remains false, i.e. keep */
 		} else
-			xdf1->changed[i] = 1;
+			xdf1->changed[i] = true;
 			/* i.e. discard */
 	}
 	xdf1->nreff = nreff;
@@ -324,9 +324,9 @@ static int xdl_cleanup_records(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xd
 		if (action2[i] == KEEP ||
 		    (action2[i] == INVESTIGATE && !xdl_clean_mmatch(action2, i, xdf2->dstart, xdf2->dend))) {
 			xdf2->rindex[nreff++] = i;
-			/* changed[i] remains 0, i.e. keep */
+			/* changed[i] remains false, i.e. keep */
 		} else
-			xdf2->changed[i] = 1;
+			xdf2->changed[i] = true;
 			/* i.e. discard */
 	}
 	xdf2->nreff = nreff;
diff --git a/xdiff/xtypes.h b/xdiff/xtypes.h
index c4b5d2d8fa..f145abba3e 100644
--- a/xdiff/xtypes.h
+++ b/xdiff/xtypes.h
@@ -48,7 +48,7 @@ typedef struct s_xdfile {
 	xrecord_t *recs;
 	long nrec;
 	long dstart, dend;
-	char *changed;
+	bool *changed;
 	long *rindex;
 	long nreff;
 } xdfile_t;