From: drh <>
Date: Fri, 12 Jun 2026 16:26:39 +0000 (+0000)
Subject: Do not use shared locks on SHM files when the filename is a long DOS-device
X-Git-Url: http://git.ipfire.org/gitweb/?a=commitdiff_plain;h=2429af2e0ce2e4c643786f8d2533f79d974e3270;p=thirdparty%2Fsqlite.git

Do not use shared locks on SHM files when the filename is a long DOS-device
path.  Only used shared locks for UNC paths.  Do not confuse the
long-DOS-device syntax with UNC paths.

FossilOrigin-Name: a4691489f21bb1645bb8de649268dd457af53c5f613f2a7fd2e5569f029efa87
---

diff --git a/manifest b/manifest
index c4a7774f23..863825c988 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Fix\sa\sbuffer\soverwrite\sin\sfts3\sthat\scould\soccur\swhile\sprocessing\sNEAR\squeries\sagainst\scorrupt\srecords.\sBug\s[bugs:/info/2026-06-11T23:11:26Z\s|\s2026-06-11T23:11:26Z].
-D 2026-06-12T15:36:26.954
+C Do\snot\suse\sshared\slocks\son\sSHM\sfiles\swhen\sthe\sfilename\sis\sa\slong\sDOS-device\npath.\s\sOnly\sused\sshared\slocks\sfor\sUNC\spaths.\s\sDo\snot\sconfuse\sthe\nlong-DOS-device\ssyntax\swith\sUNC\spaths.
+D 2026-06-12T16:26:39.327
 F .fossil-settings/binary-glob 61195414528fb3ea9693577e1980230d78a1f8b0a54c78cf1b9b24d0a409ed6a x
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
@@ -724,7 +724,7 @@ F src/os_common.h 6c0eb8dd40ef3e12fe585a13e709710267a258e2c8dd1c40b1948a1d14582e
 F src/os_kv.c e7d96727db5b67e39d590a68cc61c86daf4c093c36c011a09ebfb521182ec28d
 F src/os_setup.h 8efc64eda6a6c2f221387eefc2e7e45fd5a3d5c8337a7a83519ba4fbd2957ae2
 F src/os_unix.c 83759942d1ea8d59daed50901c123016f845fada74caf3496b8a2537c9a08838
-F src/os_win.c 8df4b34ec6a08616a7ac33164999524ef773fa359d39ae9ae0e7e1ae4f167440
+F src/os_win.c 68b1c31693a5aeeb8126f618c95f7b53fb39e254836f9a95fbf2733461a7e01d
 F src/os_win.h c06ccc3a090cf54202ea58981c298817f3309d4c9e4d52ad0a02927346493721
 F src/pager.c e0b3b6e39c3a783957d640b28401401d1f3c556803c80695958dd2b9db4ef72d
 F src/pager.h 6137149346e6c8a3ddc1eeb40aee46381e9bc8b0fcc6dda8a1efde993c2275b8
@@ -2209,8 +2209,8 @@ F tool/warnings-clang.sh bbf6a1e685e534c92ec2bfba5b1745f34fb6f0bc2a362850723a9ee
 F tool/warnings.sh a554d13f6e5cf3760f041b87939e3d616ec6961859c3245e8ef701d1eafc2ca2
 F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
 F tool/winmain.c 00c8fb88e365c9017db14c73d3c78af62194d9644feaf60e220ab0f411f3604c
-P 09ab0a1bac4eb7de651f78cfd3027b452308da7e04c4ccd7f46c402c82fd6ca5
-R 5967f3842d7d977e9300115cbcd6053f
-U dan
-Z 04945b84a384653d50d2edd356b79f0b
+P b0f773e99eb45cde0953e4870a0a7436c35277c95146fdab3aa06ebbc076c79e
+R cbde54c8d4660413f5a887e1f51ea106
+U drh
+Z 0f121de5fdb547ed55f9fd6c5dd9eb75
 # Remove this line to create a well-formed Fossil manifest.
diff --git a/manifest.uuid b/manifest.uuid
index 0c317896b5..378cb7cf86 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-b0f773e99eb45cde0953e4870a0a7436c35277c95146fdab3aa06ebbc076c79e
+a4691489f21bb1645bb8de649268dd457af53c5f613f2a7fd2e5569f029efa87
diff --git a/src/os_win.c b/src/os_win.c
index 5faff4d7a1..2fcfce0afc 100644
--- a/src/os_win.c
+++ b/src/os_win.c
@@ -3257,11 +3257,29 @@ int sqlite3_win_test_unc_locking = 0;
 
 /*
 ** Return true if the string passed as the only argument is likely
-** to be a UNC path. In other words, if it starts with "\\".
+** to be a UNC path.  Return false if note.
+**
+** Return true if:
+**
+**   (1) The name begins with "\\"
+**   (2) But does not begin with "\\?\C:\" where C can be any alphabetic
+**       character.
+**
+** For testing, also return true in all cases if the global variable
+** sqlite3_win_test_unc_locking is true.
 */
 static int winIsUNCPath(const char *zFile){
   if( zFile[0]=='\\' && zFile[1]=='\\' ){
-    return 1;
+    if( zFile[2]=='?'
+     && zFile[3]=='\\'
+     && sqlite3Isalpha(zFile[4])
+     && zFile[5]==':'
+     && winIsDirSep(zFile[6])
+    ){
+      return sqlite3_win_test_unc_locking;
+    }else{
+      return 1;
+    }
   }
   return sqlite3_win_test_unc_locking;
 }