When opening a zero-size database on unix, write one byte into the file before

interrogating the inode number.  This works around issues with msdos
filesystems mounted on OS-X.  Ticket #3260. (CVS 5504)

FossilOrigin-Name: a480a8845fb3b49967de0790b30e6250c824b9be

5 files changed, 51 insertions, 15 deletions

diff --git a/manifest b/manifest
index efd953eb3..f2e8880c8 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C In\sthe\sunix\sOS\simplementation,\sreplace\sinode\shash\stables\swith\slinked\slists.\s(CVS\s5503)
-D 2008-07-30T15:27:54
+C When\sopening\sa\szero-size\sdatabase\son\sunix,\swrite\sone\sbyte\sinto\sthe\sfile\sbefore\ninterrogating\sthe\sinode\snumber.\s\sThis\sworks\saround\sissues\swith\smsdos\nfilesystems\smounted\son\sOS-X.\s\sTicket\s#3260.\s(CVS\s5504)
+D 2008-07-30T17:28:04
 F Makefile.arm-wince-mingw32ce-gcc fcd5e9cd67fe88836360bb4f9ef4cb7f8e2fb5a0
 F Makefile.in bbb62eecc851379aef5a48a1bf8787eb13e6ec06
 F Makefile.linux-gcc d53183f4aa6a9192d249731c90dbdffbd2c68654
@@ -133,7 +133,7 @@ F src/os.c 939ae7690a01d9401685ba124b4ba45fd4a7a2ad
 F src/os.h ef8abeb9afc694b82dbd169a91c9b7e26db3c892
 F src/os_common.h 24525d8b7bce66c374dfc1810a6c9043f3359b60
 F src/os_os2.c 676ed273b17bd260f905df81375c9f9950d85517
-F src/os_unix.c c778a6b7098f54ee2e4420150265ad3d26824c96
+F src/os_unix.c fe0dbc35bcd3de49e46b132abfc0f45d6dd6a864
 F src/os_win.c 50ec783403b418ddc9e6e05d541c6027dfd41070
 F src/pager.c a6ecad26297469a8a3d1fd7a7c3dc2d603955044
 F src/pager.h 588c1ac195228b2da45c4e5f7ab6c2fd253d1751
@@ -355,7 +355,7 @@ F test/in3.test dc62b080ed79898121c61c91118b4d1e111f1438
 F test/incrblob.test 4455fffd08b2f9418a9257e18b135d72273eff3e
 F test/incrblob2.test c82a780356bdf4d0c77f1adf0ea888248904fc07
 F test/incrblob_err.test c577c91d4ed9e8336cdb188b15d6ee2a6fe9604e
-F test/incrvacuum.test 1a2b0bddc76629afeb41e3d8ea3e4563982d16b9
+F test/incrvacuum.test 0684fbd7773eec45b911d46a6f8dc0f220b1223d
 F test/incrvacuum2.test 46ef65f377e3937cfd1ba66e818309dab46f590d
 F test/incrvacuum_ioerr.test 57d2f5777ab13fa03b87b262a4ea1bad5cfc0291
 F test/index.test cbf301cdb2da43e4eac636c3400c2439af1834ad
@@ -368,7 +368,7 @@ F test/insert4.test 6e382eaf7295a4463e6f29ea20fcd8e63d097eeb
 F test/insert5.test 509017213328147d3acdfa2c441bfd82362dda41
 F test/interrupt.test 42e7cf98646fd9cb4a3b131a93ed3c50b9e149f1
 F test/intpkey.test 537669fd535f62632ca64828e435b9e54e8d677f
-F test/io.test 833a1746518ec3005aa7792f9bcb8f01923ff544
+F test/io.test 23c52939ebf90f00d9cbd819ced6daa9f21445fa
 F test/ioerr.test b42f249c9181b5864e53fdae38ef75475d71c66f
 F test/ioerr2.test 5598405c48842c6c0187daad9eb49eff2c54f80d
 F test/ioerr3.test d3cec5e1a11ad6d27527d0d38573fbff14c71bdd
@@ -614,7 +614,7 @@ F tool/speedtest16.c c8a9c793df96db7e4933f0852abb7a03d48f2e81
 F tool/speedtest2.tcl ee2149167303ba8e95af97873c575c3e0fab58ff
 F tool/speedtest8.c 1dbced29de5f59ba2ebf877edcadf171540374d1
 F tool/speedtest8inst1.c 293327bc76823f473684d589a8160bde1f52c14e
-P da0e4bff30a77f72ae283406b547401c2ebb42c5
-R 4761a1459dbfe21d158c4e02d11ac727
+P db4022db64dc5864e6f1d0a20672183879ad43aa
+R 46a59a75e0405426ca6be3fd6558aebe
 U drh
-Z 2fbbc6538919439da5b60f94f6787348
+Z f2a23010508f2b32889d0e3805823d10
diff --git a/manifest.uuid b/manifest.uuid
index 660828ab4..813079e02 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-db4022db64dc5864e6f1d0a20672183879ad43aa
\ No newline at end of file
+a480a8845fb3b49967de0790b30e6250c824b9be
\ No newline at end of file
diff --git a/src/os_unix.c b/src/os_unix.c
index 48d2ff176..4874a6437 100644
--- a/src/os_unix.c
+++ b/src/os_unix.c
@@ -12,7 +12,7 @@
 **
 ** This file contains code that is specific to Unix systems.
 **
-** $Id: os_unix.c,v 1.194 2008/07/30 15:27:54 drh Exp $
+** $Id: os_unix.c,v 1.195 2008/07/30 17:28:04 drh Exp $
 */
 #include "sqliteInt.h"
 #if SQLITE_OS_UNIX              /* This file is used on unix only */
@@ -674,6 +674,24 @@ static int findLockInfo(
     return SQLITE_IOERR;
   }
 
+  /* On OS X on an msdos filesystem, the inode number is reported
+  ** incorrectly for zero-size files.  See ticket #3260.  To work
+  ** around this problem (we consider it a bug in OS X, not SQLite)
+  ** we always increase the file size to 1 by writing a single byte
+  ** prior to accessing the inode number.  The one byte written is
+  ** an ASCII 'S' character which also happens to be the first byte
+  ** in the header of every SQLite database.  In this way, if there
+  ** is a race condition such that another thread has already populated
+  ** the first page of the database, no damage is done.
+  */
+  if( statbuf.st_size==0 ){
+    write(fd, "S", 1);
+    rc = fstat(fd, &statbuf);
+    if( rc!=0 ){
+      return SQLITE_IOERR;
+    }
+  }
+
   memset(&key1, 0, sizeof(key1));
   key1.dev = statbuf.st_dev;
   key1.ino = statbuf.st_ino;
@@ -1092,6 +1110,16 @@ static int unixFileSize(sqlite3_file *id, i64 *pSize){
     return SQLITE_IOERR_FSTAT;
   }
   *pSize = buf.st_size;
+
+  /* When opening a zero-size database, the findLockInfo() procedure
+  ** writes a single byte into that file in order to work around a bug
+  ** in the OS-X msdos filesystem.  In order to avoid problems with upper
+  ** layers, we need to report this file size as zero even though it is
+  ** really 1.   Ticket #3260.
+  */
+  if( *pSize==1 ) *pSize = 0;
+
+
   return SQLITE_OK;
 }
 
diff --git a/test/incrvacuum.test b/test/incrvacuum.test
index aebe2178d..04ea03d04 100644
--- a/test/incrvacuum.test
+++ b/test/incrvacuum.test
@@ -14,7 +14,7 @@
 # Note: There are also some tests for incremental vacuum and IO 
 # errors in incrvacuum_ioerr.test.
 #
-# $Id: incrvacuum.test,v 1.18 2008/01/21 16:22:46 drh Exp $
+# $Id: incrvacuum.test,v 1.19 2008/07/30 17:28:04 drh Exp $
 
 set testdir [file dirname $argv0]
 source $testdir/tester.tcl
@@ -35,7 +35,10 @@ do_test incrvacuum-1.1 {
   }
 } $sqlite_options(default_autovacuum)
 do_test incrvacuum-1.2.0 {
-  expr {[file size test.db] > 0}
+  # File size is sometimes 1 instead of 0 due to the hack we put in
+  # to work around ticket #3260.  Search for comments on #3260 in
+  # os_unix.c.
+  expr {[file size test.db] > 1}
 } {0}
 do_test incrvacuum-1.2 {
   # This command will create the database.
@@ -689,7 +692,10 @@ sqlite3 db test.db  ;  set ::DB [sqlite3_connection_pointer db]
 sqlite3 db2 test.db
 
 do_test incrvacuum-13.1 {
-  expr {[file size test.db]>0}
+  # File size is sometimes 1 instead of 0 due to the hack we put in
+  # to work around ticket #3260.  Search for comments on #3260 in
+  # os_unix.c.
+  expr {[file size test.db]>1}
 } {0}
 do_test incrvacuum-13.2 {
   set ::STMT [sqlite3_prepare $::DB {PRAGMA auto_vacuum = 2} -1 DUMMY]
diff --git a/test/io.test b/test/io.test
index b0a6063e7..12c756aca 100644
--- a/test/io.test
+++ b/test/io.test
@@ -13,7 +13,7 @@
 # IO traffic generated by SQLite (making sure SQLite is not writing out
 # more database pages than it has to, stuff like that).
 #
-# $Id: io.test,v 1.16 2008/05/01 18:01:47 drh Exp $
+# $Id: io.test,v 1.17 2008/07/30 17:28:04 drh Exp $
 
 set testdir [file dirname $argv0]
 source $testdir/tester.tcl
@@ -375,7 +375,9 @@ ifcapable pager_pragmas {
     db eval {
       PRAGMA auto_vacuum=OFF;
     }
-    file size test.db
+    # File size might be 1 due to the hack to work around ticket #3260.
+    # Search for #3260 in os_unix.c for additional information.
+    expr {[file size test.db]>1}
   } {0}
   do_test io-3.2 {
     execsql { CREATE TABLE abc(a, b) }