Fix some divide-by-zero errors that could occur when handling corrupt tombstone hash records.

FossilOrigin-Name: 7567ca0676f0d45026f5cd4f3fbcd09119c2eaab8ec1711499609c16c452b5e4

ext/fts5/fts5_index.c

@@ -3099,6 +3099,9 @@ static void fts5MultiIterSetEof(Fts5Iter *pIter){
 */
 #define TOMBSTONE_KEYSIZE(pPg) (pPg->p[0]==4 ? 4 : 8)
 
+#define TOMBSTONE_NSLOT(pPg)   \
+  ((pPg->nn > 16) ? ((pPg->nn-8) / TOMBSTONE_KEYSIZE(pPg)) : 1)
+
 /*
 ** Query a single tombstone hash table for rowid iRowid. Return true if
 ** it is found or false otherwise. The tombstone hash table is one of
@@ -3110,7 +3113,7 @@ static int fts5IndexTombstoneQuery(
   u64 iRowid                      /* Rowid to query hash for */
 ){
   const int szKey = TOMBSTONE_KEYSIZE(pHash);
-  const int nSlot = (pHash->nn - 8) / szKey;
+  const int nSlot = TOMBSTONE_NSLOT(pHash);
   int iSlot = (iRowid / nHashTable) % nSlot;
   int nCollide = nSlot;
 
@@ -6554,7 +6557,7 @@ static int fts5IndexTombstoneAddToPage(
   u64 iRowid
 ){
   const int szKey = TOMBSTONE_KEYSIZE(pPg);
-  const int nSlot = (pPg->nn - 8) / szKey;
+  const int nSlot = TOMBSTONE_NSLOT(pPg);
   const int nElem = fts5GetU32(&pPg->p[4]);
   int iSlot = (iRowid / nPg) % nSlot;
   int nCollide = nSlot;

ext/fts5/test/fts5contentless3.test

@@ -29,6 +29,10 @@ do_execsql_test 1.0 {
     INSERT INTO ft VALUES('three three three');
     INSERT INTO ft VALUES('four four four');
     INSERT INTO ft VALUES('five five five');
+    INSERT INTO ft VALUES('six six six');
+    INSERT INTO ft VALUES('seven seven seven');
+    INSERT INTO ft VALUES('eight eight eight');
+    INSERT INTO ft VALUES('nine nine nine');
   COMMIT;
 
   DELETE FROM ft WHERE rowid=3;
@@ -71,6 +75,22 @@ do_execsql_test 1.5 {
   DELETE FROM ft WHERE rowid=4
 }
 
+do_execsql_test 1.6 {
+  UPDATE ft_data SET block = myhex('04000000 00000000')
+    WHERE id = (SELECT max(id) FROM ft_data);
+}
+do_execsql_test 1.7 {
+  SELECT rowid FROM ft('two');
+} {2}
+
+do_execsql_test 1.8 {
+  UPDATE ft_data SET block = myhex('04000000 00000000')
+    WHERE id = (SELECT max(id) FROM ft_data);
+}
+do_execsql_test 1.9 {
+  DELETE FROM ft WHERE rowid=8
+} {}
+
 
 finish_test
 

manifest

@@ -1,5 +1,5 @@
-C Avoid\san\sinfinite\sloop\sthat\scould\sbe\sentered\swhen\sdealing\swith\scorrupt\sfts5\stombstone\shash\spages.
-D 2023-07-20T20:09:26.394
+C Fix\ssome\sdivide-by-zero\serrors\sthat\scould\soccur\swhen\shandling\scorrupt\stombstone\shash\srecords.
+D 2023-07-20T20:29:56.954
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -92,7 +92,7 @@ F ext/fts5/fts5_buffer.c 3001fbabb585d6de52947b44b455235072b741038391f830d6b7292
 F ext/fts5/fts5_config.c 010fabcc0aaa0dfa76b19146e8bddf7de368933eeac01e294af6607447500caa
 F ext/fts5/fts5_expr.c 2473c13542f463cae4b938c498d6193c90d38ea1a2a4f9849c0479736e50d24d
 F ext/fts5/fts5_hash.c d4fb70940359f2120ccd1de7ffe64cc3efe65de9e8995b822cd536ff64c96982
-F ext/fts5/fts5_index.c 5b5b9944ef97bf9aa0726fdbd82552d488b6fcee32e086e6d32ea9934e1809e2
+F ext/fts5/fts5_index.c db653198e9bb76d285df246df1f14ebf3f1cfcbca0605f2bf272026f52021011
 F ext/fts5/fts5_main.c ede405f0f11db562653b988d043a531daa66093b46c1b35b8fcddb54819cba84
 F ext/fts5/fts5_storage.c 3c9b41fce41b6410f2e8f82eb035c6a29b2560483f773e6dc98cf3cb2e4ddbb5
 F ext/fts5/fts5_tcl.c b1445cbe69908c411df8084a10b2485500ac70a9c747cdc8cda175a3da59d8ae
@@ -134,7 +134,7 @@ F ext/fts5/test/fts5connect.test 08030168fc96fc278fa81f28654fb7e90566f33aff269c0
 F ext/fts5/test/fts5content.test 213506436fb2c87567b8e31f6d43ab30aab99354cec74ed679f22aad0cdbf283
 F ext/fts5/test/fts5contentless.test 9a42a86822670792ba632f5c57459addeb774d93b29d5e6ddae08faa64c2b6d9
 F ext/fts5/test/fts5contentless2.test 12c778d134a121b8bad000fbf3ae900d53226fee840ce36fe941b92737f1fda7
-F ext/fts5/test/fts5contentless3.test db92625a2e3f9e5ba047ce8ded58c825affce45cc711ed6d7c96fe54b95894a1
+F ext/fts5/test/fts5contentless3.test b773267d7d5434d0a503b9d73de240f5769efb0e3576e133dd76eccb318116bc
 F ext/fts5/test/fts5corrupt.test 77ae6f41a7eba10620efb921cf7dbe218b0ef232b04519deb43581cb17a57ebe
 F ext/fts5/test/fts5corrupt2.test 7453752ba12ce91690c469a6449d412561cc604b1dec994e16ab132952e7805f
 F ext/fts5/test/fts5corrupt3.test 7da9895dafa404efd20728f66ff4b94399788bdc042c36fe2689801bba2ccd78
@@ -2047,8 +2047,8 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 5aac50e92e956b15367c75c20c17bc1c75e84e2752bfffe4ad0a266cb9bd3b8a
-R a2bc7a639e489f4200810e70aeab413a
+P 69ce2ce035279f2a00c2238187cf4d2a9092c3410f5900e4613fe4e46311169e
+R 716993a5a4c359e4b4afccc9c55270f5
 U dan
-Z 36cb6c12a15fce5364a14d77012ed267
+Z f01327fd76f39e2a6bc2b85c23603eff
 # Remove this line to create a well-formed Fossil manifest.

manifest.uuid

@@ -1 +1 @@
-69ce2ce035279f2a00c2238187cf4d2a9092c3410f5900e4613fe4e46311169e
+7567ca0676f0d45026f5cd4f3fbcd09119c2eaab8ec1711499609c16c452b5e4