Hello ,developers on sqlite.
I'm Ralph Zhang from Zoom, as an user of your open source porduct.
I have found an issue that the newest sqlite cannot open db on one of our HP customized Linux PC. 
We have testing the sqlite code on this PC and finally found the return error place is the new add static int unixFullPathname() function.

the new function is like 
static int unixFullPathname(
  sqlite3_vfs *pVfs,            /* Pointer to vfs object */
  const char *zPath,            /* Possibly relative input path */
  int nOut,                     /* Size of output buffer in bytes */
  char *zOut                    /* Output buffer */
){
  DbPath path;
  UNUSED_PARAMETER(pVfs);
  path.rc = 0;
  path.nUsed = 0;
  path.nSymlink = 0;
  path.nOut = nOut;
  path.zOut = zOut;
  if( zPath[0]!='/' ){
    char zPwd[SQLITE_MAX_PATHLEN+2];
    if( osGetcwd(zPwd, sizeof(zPwd)-2)==0 ){
      return unixLogError(SQLITE_CANTOPEN_BKPT, "getcwd", zPath);
    }
    appendAllPathElements(&path, zPwd);
  }
  appendAllPathElements(&path, zPath);
  zOut[path.nUsed] = 0;
  if( path.rc || path.nUsed<2 ) return SQLITE_CANTOPEN_BKPT;
  if( path.nSymlink ) return SQLITE_OK_SYMLINK;
  return SQLITE_OK;
}

It looks like to expand the full path on unix.
In the HP's system, the file path is " /home/user/xxx " ,but the "home" path is linked to "../writalbe/home" actually.
So the input path will be expand to "../writalbe/home/user/xxx " by  osGetcwd(zPwd, sizeof(zPwd)-2)==0.
Then when the function call   appendAllPathElements(&path, zPwd);
IT will return error at 
if( nName==1 ) return;
    if( zName[1]=='.' && nName==2 ){
      if( pPath->nUsed<=1 ){
        pPath->rc = SQLITE_ERROR;
        return;
      }
bacause the path now is "../writalbe/home/user/xxx " start with "../" ,It's a relative path.

And it works good on old version of sqlite.

So does it have some security concerns that make this change? The path might be linked as relative path in some system, I think we can fix the issue in this case by changing the expand and check path order.

If you have any updates, please contact me at ralph.zhang@zoom.us. Thanks!