Merge the winAccess retry logic from the anti-antivirus branch

into the trunk.

FossilOrigin-Name: 08d0e8799e1441ef063b1cdf9e4107071a0f81ca

src/os_common.h

@@ -30,10 +30,13 @@
 #endif
 
 #ifdef SQLITE_DEBUG
-int sqlite3OSTrace = 0;
-#define OSTRACE(X)          if( sqlite3OSTrace ) sqlite3DebugPrintf X
+# ifndef SQLITE_DEBUG_OS_TRACE
+#   define SQLITE_DEBUG_OS_TRACE 0
+# endif
+  int sqlite3OSTrace = SQLITE_DEBUG_OS_TRACE;
+# define OSTRACE(X)          if( sqlite3OSTrace ) sqlite3DebugPrintf X
 #else
-#define OSTRACE(X)
+# define OSTRACE(X)
 #endif
 
 /*

src/os_win.c

@@ -2452,11 +2452,13 @@ static int winAccess(
     return SQLITE_NOMEM;
   }
   if( isNT() ){
+    int cnt = 0;
     WIN32_FILE_ATTRIBUTE_DATA sAttrData;
     memset(&sAttrData, 0, sizeof(sAttrData));
-    if( GetFileAttributesExW((WCHAR*)zConverted,
+    while( (rc = GetFileAttributesExW((WCHAR*)zConverted,
                              GetFileExInfoStandard, 
-                             &sAttrData) ){
+                             &sAttrData)) && rc==0 && retryIoerr(&cnt) ){}
+    if( rc ){
       /* For an SQLITE_ACCESS_EXISTS query, treat a zero-length file
       ** as if it does not exist.
       */