Fix a problem causing the write-lock to be held when it should not be in some circumstances following a SEH exception.

FossilOrigin-Name: 7eb5accb7cf937fc967dcd86da0af813fb18a2697348bd231fbefd3c09b930ab

manifest

@@ -1,5 +1,5 @@
-C Have\ssqlite3_enable_setlk(-1)\sconfigure\sindefinite\sblocking\slocks\swhere\sthey\sare\ssupported.
-D 2025-01-30T15:26:16.127
+C Fix\sa\sproblem\scausing\sthe\swrite-lock\sto\sbe\sheld\swhen\sit\sshould\snot\sbe\sin\ssome\scircumstances\sfollowing\sa\sSEH\sexception.
+D 2025-01-30T17:04:28.336
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md e108e1e69ae8e8a59e93c455654b8ac9356a11720d3345df2a4743e9590fb20d
@@ -858,7 +858,7 @@ F src/vdbetrace.c fe0bc29ebd4e02c8bc5c1945f1d2e6be5927ec12c06d89b03ef2a4def34bf8
 F src/vdbevtab.c fc46b9cbd759dc013f0b3724549cc0d71379183c667df3a5988f7e2f1bd485f3
 F src/vtab.c 316cd48e9320660db3047cd306cd056e4361180cebb4d0f10a39244e10c11422
 F src/vxworks.h d2988f4e5a61a4dfe82c6524dd3d6e4f2ce3cdb9
-F src/wal.c 20550245b9a82f94736e905ee7df8f549e1301ba40e9f2cb51139e36d49c3c0f
+F src/wal.c 6da5a05c124bad1e530cf83bafa07d28afdda20c28b276de49948ef8295d9e84
 F src/wal.h ba252daaa94f889f4b2c17c027e823d9be47ce39da1d3799886bbd51f0490452
 F src/walker.c d5006d6b005e4ea7302ad390957a8d41ed83faa177e412f89bc5600a7462a014
 F src/where.c 9ad3dea8003a8913da6a4ca8322e2fe30773f46e88a0d4fbf9db13bdb999efa2
@@ -2022,7 +2022,7 @@ F test/walro2.test 33955a6fd874dd9724005e17f77fef89d334b3171454a1256fe4941a96766
 F test/walrofault.test c70cb6e308c443867701856cce92ad8288cd99488fa52afab77cca6cfd51af68
 F test/walseh1.test bae700eb99519b6d5cd3f893c04759accc5a59c391d4189fe4dd6995a533442b
 F test/walsetlk.test 9c5b92f9a20252540fedf9ffa6ee3d1b8af08ea4b80d0144d9b88e6c0c1de80d
-F test/walsetlk2.test def90f1c8cf47c5128bd3d12171ff1ed6c79f78dcb50c8c2cacf030fc78566a0
+F test/walsetlk2.test 5ae8662a28c013e8df2ce975f9e3577a7f239aeb4622bb8d4d0ca8e16c0c132e
 F test/walshared.test 42e3808582504878af237ea02c42ca793e8a0efaa19df7df26ac573370dbc7a3
 F test/walslow.test 0c51843836c9dcf40a5ac05aa781bfb977b396ee2c872d92bd48b79d5dd9aa23
 F test/walthread.test 14b20fcfa6ae152f5d8e12f5dc8a8a724b7ef189f5d8ef1e2ceab79f2af51747
@@ -2203,8 +2203,8 @@ F tool/version-info.c 3b36468a90faf1bbd59c65fd0eb66522d9f941eedd364fabccd7227350
 F tool/warnings-clang.sh bbf6a1e685e534c92ec2bfba5b1745f34fb6f0bc2a362850723a9ee87c1b31a7
 F tool/warnings.sh 49a486c5069de041aedcbde4de178293e0463ae9918ecad7539eedf0ec77a139
 F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
-P 4a7eb492797abb47b18b7dfc557aeae43a0dea5b861efc203398d5059b10d131
-R 742ff1ca774eae27b30e6d13698e33be
+P 62009565d2f2a2c4d347e1da0d5b4ad43056742df47fd6ddb92e62f53a2b57f1
+R 1ce6d89df3820633838b6629306f6da1
 U dan
-Z 0c159766f95122a144fb984bb53f46a1
+Z ed92d59f35c33d93aa0b00d0344b6f87
 # Remove this line to create a well-formed Fossil manifest.

manifest.uuid

@@ -1 +1 @@
-62009565d2f2a2c4d347e1da0d5b4ad43056742df47fd6ddb92e62f53a2b57f1
+7eb5accb7cf937fc967dcd86da0af813fb18a2697348bd231fbefd3c09b930ab

src/wal.c

@@ -502,6 +502,11 @@ struct WalCkptInfo {
 /*
 ** An open write-ahead log file is represented by an instance of the
 ** following object.
+**
+** writeLock:
+**   This is usually set to 1 whenever the WRITER lock is held. However,
+**   if it is set to 2, then the WRITER lock is held but must be released
+**   by walHandleException() if a SEH exception is thrown.
 */
 struct Wal {
   sqlite3_vfs *pVfs;         /* The VFS used to create pDbFd */
@@ -2413,7 +2418,9 @@ static int walHandleException(Wal *pWal){
     static const int S = 1;
     static const int E = (1<<SQLITE_SHM_NLOCK);
     int ii;
-    u32 mUnlock = pWal->lockMask & ~(
+    u32 mUnlock;
+    if( pWal->writeLock==2 ) pWal->writeLock = 0;
+    mUnlock = pWal->lockMask & ~(
         (pWal->readLock<0 ? 0 : (S << WAL_READ_LOCK(pWal->readLock)))
         | (pWal->writeLock ? (E << WAL_WRITE_LOCK) : 0)
         | (pWal->ckptLock ? (E << WAL_CKPT_LOCK) : 0)
@@ -2685,7 +2692,12 @@ static int walIndexReadHdr(Wal *pWal, int *pChanged){
       if( bWriteLock 
        || SQLITE_OK==(rc = walLockExclusive(pWal, WAL_WRITE_LOCK, 1)) 
       ){
-        pWal->writeLock = 1;
+        /* If the write-lock was just obtained, set writeLock to 2 instead of
+        ** the usual 1. This causes walIndexPage() to behave as if the 
+        ** write-lock were held (so that it allocates new pages as required),
+        ** and walHandleException() to unlock the write-lock if a SEH exception
+        ** is thrown.  */
+        if( !bWriteLock ) pWal->writeLock = 2;
         if( SQLITE_OK==(rc = walIndexPage(pWal, 0, &page0)) ){
           badHdr = walIndexTryHdr(pWal, pChanged);
           if( badHdr ){

test/walsetlk2.test

@@ -110,6 +110,7 @@ testfixture_nb done {
   db eval {
     COMMIT
   }
+  db close
 }
 
 after 500 {set ok 1}
@@ -154,6 +155,7 @@ testfixture_nb done {
   db eval {
     COMMIT
   }
+  db close
 }
 
 after 500 {set ok 1}
@@ -194,6 +196,7 @@ testfixture_nb done {
   db eval {
     COMMIT
   }
+  db close
 }
 
 after 500 {set ok 1}
@@ -216,6 +219,7 @@ testfixture_nb done {
   db eval {
     COMMIT
   }
+  db close
 }
 
 after 500 {set ok 1}