commit 4861c9da86ada01cffa2ce3801f670587e896ce2
from: Neels Hofmeyr <neels@hofmeyr.de>
date: Fri Oct 30 03:55:03 2020 UTC

add sanity assertions around adding result chunks

uncovers errors related to placing minus chunks above already added plus
chunks.

commit - 6303eedc563848baa1f4c48ccdb70b80393255d6
commit + 4861c9da86ada01cffa2ce3801f670587e896ce2
blob - 1d0c6fd4faa11438034964c34bfb319969e36bff
blob + 13fb82c4b8e75e74ec16e8b30fea6c29fd41efb3
--- lib/diff_main.c
+++ lib/diff_main.c
@@ -233,6 +233,14 @@ diff_state_add_solved_chunk(struct diff_state *state,
 	debug_dump_atoms(&state->left, chunk->left_start, chunk->left_count);
 	debug("R\n");
 	debug_dump_atoms(&state->right, chunk->right_start, chunk->right_count);
+
+	if (result->len) {
+		last = &result->head[result->len - 1];
+		assert(chunk->left_start
+		       == last->left_start + last->left_count);
+		assert(chunk->right_start
+		       == last->right_start + last->right_count);
+	}
 
 	if (new_t == last_t) {
 		new_chunk = &result->head[result->len - 1];
blob - c7749377c1c41c1fee60256db169cee8ece8fd9e
blob + 3945cbb5448b10d07a96553307d4786990824929
--- lib/diff_output_unidiff.c
+++ lib/diff_output_unidiff.c
@@ -20,6 +20,7 @@
 #include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <assert.h>
 
 #include <arraylist.h>
 #include <diff_main.h>
@@ -397,6 +398,7 @@ diff_output_unidiff(struct diff_output_info **output_i
 	    result->right->root->diff_flags);
 	bool show_function_prototypes = (flags & DIFF_FLAG_SHOW_PROTOTYPES);
 	int i;
+	unsigned int check_left_pos, check_right_pos;
 
 	if (!result)
 		return EINVAL;
@@ -420,6 +422,8 @@ diff_output_unidiff(struct diff_output_info **output_i
 	}
 
 #if DEBUG
+	check_left_pos = 0;
+	check_right_pos = 0;
 	for (i = 0; i < result->chunks.len; i++) {
 		struct diff_chunk *c = &result->chunks.head[i];
 		enum diff_chunk_type t = diff_chunk_type(c);
@@ -432,7 +436,14 @@ diff_output_unidiff(struct diff_output_info **output_i
 		      c->right_count,
 		      c->left_start ? diff_atom_root_idx(result->left, c->left_start) : -1,
 		      c->right_start ? diff_atom_root_idx(result->right, c->right_start) : -1);
+		assert(check_left_pos == diff_atom_root_idx(result->left, c->left_start));
+		assert(check_right_pos == diff_atom_root_idx(result->right, c->right_start));
+		check_left_pos += c->left_count;
+		check_right_pos += c->right_count;
+
 	}
+	assert(check_left_pos == result->left->atoms.len);
+	assert(check_right_pos == result->right->atoms.len);
 #endif
 
 	for (i = 0; i < result->chunks.len; i++) {