SQLite

#else
  { "mremap",       (sqlite3_syscall_ptr)0,               0 },
#endif
#define osMremap ((void*(*)(void*,size_t,size_t,int,...))aSyscall[23].pCurrent)
  { "getpagesize",  (sqlite3_syscall_ptr)unixGetpagesize, 0 },
#define osGetpagesize ((int(*)(void))aSyscall[24].pCurrent)

  { "readlink",     (sqlite3_syscall_ptr)readlink,        0 },
#define osReadlink ((ssize_t(*)(const char*,char*,size_t))aSyscall[25].pCurrent)

#endif

}; /* End of the overrideable system calls */

/*
** This is the xSetSystemCall() method of sqlite3_vfs for all of the
** "unix" VFSes.  Return SQLITE_OK opon successfully updating the

*/
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 */
){
  int nByte;

  /* It's odd to simulate an io-error here, but really this is just
  ** using the io-error infrastructure to test that SQLite handles this
  ** function failing. This function could fail if, for example, the
  ** current working directory has been unlinked.
  */
  SimulateIOError( return SQLITE_ERROR );

  assert( pVfs->mxPathname==MAX_PATHNAME );
  UNUSED_PARAMETER(pVfs);

  /* Attempt to resolve the path as if it were a symbolic link. If it is
  ** a symbolic link, the resolved path is stored in buffer zOut[]. Or, if
  ** the identified file is not a symbolic link or does not exist, then
  ** zPath is copied directly into zOut. Either way, nByte is left set to
  ** the size of the string copied into zOut[] in bytes.  */
  nByte = osReadlink(zPath, zOut, nOut-1);
  if( nByte<0 ){
    if( errno!=EINVAL && errno!=ENOENT ){
      return unixLogError(SQLITE_CANTOPEN_BKPT, "readlink", zPath);
    }
    zOut[nOut-1] = '\0';

    sqlite3_snprintf(nOut-1, zOut, "%s", zPath);
    nByte = sqlite3Strlen30(zOut);
  }else{
    zOut[nByte] = '\0';
  }

  /* If buffer zOut[] now contains an absolute path there is nothing more
  ** to do. If it contains a relative path, do the following:
  **
  **   * move the relative path string so that it is at the end of th
  **     zOut[] buffer.
  **   * Call getcwd() to read the path of the current working directory 
  **     into the start of the zOut[] buffer.
  **   * Append a '/' character to the cwd string and move the 
  **     relative path back within the buffer so that it immediately 
  **     follows the '/'.
  **
  ** This code is written so that if the combination of the CWD and relative
  ** path are larger than the allocated size of zOut[] the CWD is silently
  ** truncated to make it fit. This is Ok, as SQLite refuses to open any
  ** file for which this function returns a full path larger than (nOut-8)
  ** bytes in size.  */
  if( zOut[0]!='/' ){
    int nCwd;
    int nRem = nOut-nByte-1;
    memmove(&zOut[nRem], zOut, nByte+1);
    zOut[nRem-1] = '\0';
    if( osGetcwd(zOut, nRem-1)==0 ){
      return unixLogError(SQLITE_CANTOPEN_BKPT, "getcwd", zPath);
    }
    nCwd = sqlite3Strlen30(zOut);
    assert( nCwd<=nRem-1 );
    zOut[nCwd] = '/';
    memmove(&zOut[nCwd+1], &zOut[nRem], nByte+1);
  }

  return SQLITE_OK;
}


#ifndef SQLITE_OMIT_LOAD_EXTENSION
/*
** Interfaces for opening a shared library, finding entry points

    UNIXVFS("unix-proxy",    proxyIoFinder ),
#endif
  };
  unsigned int i;          /* Loop counter */

  /* Double-check that the aSyscall[] array has been constructed
  ** correctly.  See ticket [bb3a86e890c8e96ab] */
  assert( ArraySize(aSyscall)==26 );

  /* Register all VFSes defined in the aVfs[] array */
  for(i=0; i<(sizeof(aVfs)/sizeof(sqlite3_vfs)); i++){
    sqlite3_vfs_register(&aVfs[i], i==0);
  }
  return SQLITE_OK; 
}

# Test a failure in open() due to the path not existing.
#
do_test 1.4.1 {
  set ::log [list]
  list [catch { sqlite3 dbh /root/test.db } msg] $msg
} {1 {unable to open database file}}

do_re_test 1.4.2 { 
  lindex $::log 0
} {^os_unix.c:\d*: \(\d+\) (open|readlink)\(.*test.db\) - }

#--------------------------------------------------------------------------
# Tests oserror-1.* test failures in the unlink() system call.
#
ifcapable wal {
  do_test 2.1.1 {
    set ::log [list]

# 2015 October 31
#
# The author disclaims copyright to this source code.  In place of
# a legal notice, here is a blessing:
#
#    May you do good and not evil.
#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
# This file implements regression tests for SQLite library.  The
# focus of this file is testing that SQLite can follow symbolic links.
#

set testdir [file dirname $argv0]
source $testdir/tester.tcl
set testprefix symlink

# This only runs on unix.
if {$::tcl_platform(platform)!="unix"} {
  finish_test
  return
}

# Ensure that test.db has been created.
#
do_execsql_test 1.0 {
  CREATE TABLE t1(x, y);
}

# Test that SQLite follows symlinks when opening files.
#
forcedelete test.db2
do_test 1.1 {
  file link test.db2 test.db
  sqlite3 db2 test.db2
  sqlite3_db_filename db2 main
} [file join [pwd] test.db]

# Test that if the symlink points to a file that does not exists, it is
# created when it is opened.
#
do_test 1.2.1 {
  db2 close
  db close
  forcedelete test.db
  file exists test.db
} 0
do_test 1.2.2 {
  sqlite3 db2 test.db2
  file exists test.db
} 1
do_test 1.2.3 {
  sqlite3_db_filename db2 main
} [file join [pwd] test.db]
db2 close

# Test that a loop of symlinks cannot be opened.
#
do_test 1.3 {
  forcedelete test.db
  # Note: Tcl [file link] command is too smart to create loops of symlinks.
  exec ln -s test.db2 test.db
  list [catch { sqlite3 db test.db } msg] $msg
} {1 {unable to open database file}}

# Test that overly large paths cannot be opened.
#
do_test 1.4 {
  set name "test.db[string repeat x 502]"
  list [catch { sqlite3 db $name } msg] $msg
} {1 {unable to open database file}}
do_test 1.5 {
  set r [expr 510 - [string length test.db] - [string length [pwd]]]
  set name "test.db[string repeat x $r]"
  list [catch { sqlite3 db $name } msg] $msg
} {1 {unable to open database file}}

#-------------------------------------------------------------------------
# Test that journal and wal files are created next to the real file,
# not the symlink.
#
do_test 2.0 {
  catch { db close }
  catch { db2 close }
  forcedelete test.db test.db2
  sqlite3 db test.db
  execsql { CREATE TABLE t1(x) }
  file link test.db2 test.db
  sqlite3 db2 test.db2
  file exists test.db-journal
} 0

do_test 2.1 {
  execsql {
    BEGIN;
      INSERT INTO t1 VALUES(1);
  } db2
  file exists test.db-journal
} 1
do_test 2.2 {
  file exists test.db2-journal
} 0
do_test 2.3 {
  execsql {
    COMMIT;
    PRAGMA journal_mode = wal;
    INSERT INTO t1 VALUES(2);
  } db2
  file exists test.db-wal
} 1
do_test 2.4 {
  file exists test.db2-wal
} 0
do_execsql_test 2.5 {
  SELECT * FROM t1;
} {1 2}

finish_test

# Tests for the xNextSystemCall method.
#
foreach s {
    open close access getcwd stat fstat ftruncate
    fcntl read pread write pwrite fchmod fallocate
    pread64 pwrite64 unlink openDirectory mkdir rmdir 
    statvfs fchown umask mmap munmap mremap
    getpagesize readlink
} {
  if {[test_syscall exists $s]} {lappend syscall_list $s}
}
do_test 3.1 { lsort [test_syscall list] } [lsort $syscall_list]

#-------------------------------------------------------------------------
# This test verifies that if a call to open() fails and errno is set to