Fix a problem with the filename normalizer in unix, discovered by dbsqlfuzz.

FossilOrigin-Name: ff1eca7fcdcbc550a5f23db9d85281e5373500912699a7c7ae54bc0df0547e26

manifest

@@ -1,5 +1,5 @@
-C New\sassert\sstatements\sassociated\swith\sEphemeral\scursors\sin\sthe\sbytecode\sengine.
-D 2021-03-18T13:19:41.275
+C Fix\sa\sproblem\swith\sthe\sfilename\snormalizer\sin\sunix,\sdiscovered\sby\sdbsqlfuzz.
+D 2021-03-18T13:55:25.762
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -526,7 +526,7 @@ F src/os.c 2d6e646370b1aa78942c68d7edf124e518963adf4a90bce87f365a5a5495529a
 F src/os.h 48388821692e87da174ea198bf96b1b2d9d83be5dfc908f673ee21fafbe0d432
 F src/os_common.h b2f4707a603e36811d9b1a13278bffd757857b85
 F src/os_setup.h 0dbaea40a7d36bf311613d31342e0b99e2536586
-F src/os_unix.c adbbcea4c63d3b400d405f60a5da4c01433753ec4a12e2dc695beb2bbd671fe9
+F src/os_unix.c 7a9eab7b11f552ab91ead980086b312c7e3b871efdee8c0c072b682bbec6592e
 F src/os_win.c 77d39873836f1831a9b0b91894fec45ab0e9ca8e067dc8c549e1d1eca1566fe9
 F src/os_win.h 7b073010f1451abe501be30d12f6bc599824944a
 F src/pager.c 970691daea03f9f15e34de671bd8675c1e136232b529e21bfd36d4dba6d41753
@@ -1910,7 +1910,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P e4c44c0bca317c03f8e6d3aa7cc88e5f96159a3d91c07257d408f7db028fd151
-R f278259754fd52f20047295482ff6a9f
+P a8ce73e2573b271d5d45838802ed1905ce5e18d5fafe0078700e79fab85457e2
+R a7058bc81a7ed447b3fd897044acb8b9
 U drh
-Z 8215ad2629ec1b5e26923675b0791bde
+Z 7bd33555fc5d9a28891bb4e7f995247b

manifest.uuid

@@ -1 +1 @@
-a8ce73e2573b271d5d45838802ed1905ce5e18d5fafe0078700e79fab85457e2
+ff1eca7fcdcbc550a5f23db9d85281e5373500912699a7c7ae54bc0df0547e26

src/os_unix.c

@@ -6361,7 +6361,8 @@ static int unixBackupDir(const char *z, int *pJ){
   int j = *pJ;
   int i;
   if( j<=0 ) return 0;
-  for(i=j-1; ALWAYS(i>0) && z[i-1]!='/'; i--){}
+  for(i=j-1; i>0 && z[i-1]!='/'; i--){}
+  if( i==0 ) return 0;
   if( z[i]=='.' && i==j-2 && z[i+1]=='.' ) return 0;
   *pJ = i-1;
   return 1;