Update tcl to version 8.5.9

[msysgit/mtrensch.git] / mingw / lib / tcl8.5 / safe.tcl

# safe.tcl --
#
# This file provide a safe loading/sourcing mechanism for safe interpreters.
# It implements a virtual path mecanism to hide the real pathnames from the
# slave. It runs in a master interpreter and sets up data structure and
# aliases that will be invoked when used from a slave interpreter.
# 
# See the safe.n man page for details.
#
# Copyright (c) 1996-1997 Sun Microsystems, Inc.
#
# See the file "license.terms" for information on usage and redistribution of
# this file, and for a DISCLAIMER OF ALL WARRANTIES.
#
# RCS: @(#) $Id: safe.tcl,v 1.16.4.8 2010/09/02 18:30:29 andreas_kupries Exp $

#
# The implementation is based on namespaces. These naming conventions are
# followed:
# Private procs starts with uppercase.
# Public  procs are exported and starts with lowercase
#

# Needed utilities package
package require opt 0.4.1

# Create the safe namespace
namespace eval ::safe {
    # Exported API:
    namespace export interpCreate interpInit interpConfigure interpDelete \
        interpAddToAccessPath interpFindInAccessPath setLogCmd
}

# Helper function to resolve the dual way of specifying staticsok (either
# by -noStatics or -statics 0)
proc ::safe::InterpStatics {} {
    foreach v {Args statics noStatics} {
        upvar $v $v
    }
    set flag [::tcl::OptProcArgGiven -noStatics]
    if {$flag && (!$noStatics == !$statics) 
        && ([::tcl::OptProcArgGiven -statics])} {
        return -code error\
            "conflicting values given for -statics and -noStatics"
    }
    if {$flag} {
        return [expr {!$noStatics}]
    } else {
        return $statics
    }
}

# Helper function to resolve the dual way of specifying nested loading
# (either by -nestedLoadOk or -nested 1)
proc ::safe::InterpNested {} {
    foreach v {Args nested nestedLoadOk} {
        upvar $v $v
    }
    set flag [::tcl::OptProcArgGiven -nestedLoadOk]
    # note that the test here is the opposite of the "InterpStatics" one
    # (it is not -noNested... because of the wanted default value)
    if {$flag && (!$nestedLoadOk != !$nested) 
        && ([::tcl::OptProcArgGiven -nested])} {
        return -code error\
            "conflicting values given for -nested and -nestedLoadOk"
    }
    if {$flag} {
        # another difference with "InterpStatics"
        return $nestedLoadOk
    } else {
        return $nested
    }
}

####
#
#  API entry points that needs argument parsing :
#
####

# Interface/entry point function and front end for "Create"
proc ::safe::interpCreate {args} {
    set Args [::tcl::OptKeyParse ::safe::interpCreate $args]
    InterpCreate $slave $accessPath \
        [InterpStatics] [InterpNested] $deleteHook
}

proc ::safe::interpInit {args} {
    set Args [::tcl::OptKeyParse ::safe::interpIC $args]
    if {![::interp exists $slave]} {
        return -code error "\"$slave\" is not an interpreter"
    }
    InterpInit $slave $accessPath \
        [InterpStatics] [InterpNested] $deleteHook
}

# Check that the given slave is "one of us"
proc ::safe::CheckInterp {slave} {
    namespace upvar ::safe S$slave state
    if {![info exists state] || ![::interp exists $slave]} {
        return -code error \
            "\"$slave\" is not an interpreter managed by ::safe::"
    }
}

# Interface/entry point function and front end for "Configure".  This code
# is awfully pedestrian because it would need more coupling and support
# between the way we store the configuration values in safe::interp's and
# the Opt package. Obviously we would like an OptConfigure to avoid
# duplicating all this code everywhere.
# -> TODO (the app should share or access easily the program/value stored
# by opt)

# This is even more complicated by the boolean flags with no values that
# we had the bad idea to support for the sake of user simplicity in
# create/init but which makes life hard in configure...
# So this will be hopefully written and some integrated with opt1.0
# (hopefully for tcl8.1 ?)
proc ::safe::interpConfigure {args} {
    switch [llength $args] {
        1 {
            # If we have exactly 1 argument the semantic is to return all
            # the current configuration. We still call OptKeyParse though
            # we know that "slave" is our given argument because it also
            # checks for the "-help" option.
            set Args [::tcl::OptKeyParse ::safe::interpIC $args]
            CheckInterp $slave
            namespace upvar ::safe S$slave state

            return [join [list \
                [list -accessPath $state(access_path)] \
                [list -statics    $state(staticsok)]   \
                [list -nested     $state(nestedok)]    \
                [list -deleteHook $state(cleanupHook)]]]
        }
        2 {
            # If we have exactly 2 arguments the semantic is a "configure
            # get"
            lassign $args slave arg

            # get the flag sub program (we 'know' about Opt's internal
            # representation of data)
            set desc [lindex [::tcl::OptKeyGetDesc ::safe::interpIC] 2]
            set hits [::tcl::OptHits desc $arg]
            if {$hits > 1} {
                return -code error [::tcl::OptAmbigous $desc $arg]
            } elseif {$hits == 0} {
                return -code error [::tcl::OptFlagUsage $desc $arg]
            }
            CheckInterp $slave
            namespace upvar ::safe S$slave state

            set item [::tcl::OptCurDesc $desc]
            set name [::tcl::OptName $item]
            switch -exact -- $name {
                -accessPath {return [list -accessPath $state(access_path)]}
                -statics    {return [list -statics    $state(staticsok)]}
                -nested     {return [list -nested     $state(nestedok)]}
                -deleteHook {return [list -deleteHook $state(cleanupHook)]}
                -noStatics {
                    # it is most probably a set in fact but we would need
                    # then to jump to the set part and it is not *sure*
                    # that it is a set action that the user want, so force
                    # it to use the unambigous -statics ?value? instead:
                    return -code error\
                        "ambigous query (get or set -noStatics ?)\
                                use -statics instead"
                }
                -nestedLoadOk {
                    return -code error\
                        "ambigous query (get or set -nestedLoadOk ?)\
                                use -nested instead"
                }
                default {
                    return -code error "unknown flag $name (bug)"
                }
            }
        }
        default {
            # Otherwise we want to parse the arguments like init and
            # create did
            set Args [::tcl::OptKeyParse ::safe::interpIC $args]
            CheckInterp $slave
            namespace upvar ::safe S$slave state

            # Get the current (and not the default) values of whatever has
            # not been given:
            if {![::tcl::OptProcArgGiven -accessPath]} {
                set doreset 1
                set accessPath $state(access_path)
            } else {
                set doreset 0
            }
            if {
                ![::tcl::OptProcArgGiven -statics]
                && ![::tcl::OptProcArgGiven -noStatics]
            } {
                set statics    $state(staticsok)
            } else {
                set statics    [InterpStatics]
            }
            if {
                [::tcl::OptProcArgGiven -nested] ||
                [::tcl::OptProcArgGiven -nestedLoadOk]
            } {
                set nested     [InterpNested]
            } else {
                set nested     $state(nestedok)
            }
            if {![::tcl::OptProcArgGiven -deleteHook]} {
                set deleteHook $state(cleanupHook)
            }
            # we can now reconfigure :
            InterpSetConfig $slave $accessPath $statics $nested $deleteHook
            # auto_reset the slave (to completly synch the new access_path)
            if {$doreset} {
                if {[catch {::interp eval $slave {auto_reset}} msg]} {
                    Log $slave "auto_reset failed: $msg"
                } else {
                    Log $slave "successful auto_reset" NOTICE
                }
            }
        }
    }
}

####
#
#  Functions that actually implements the exported APIs
#
####

#
# safe::InterpCreate : doing the real job
#
# This procedure creates a safe slave and initializes it with the safe
# base aliases.
# NB: slave name must be simple alphanumeric string, no spaces, no (), no
# {},...  {because the state array is stored as part of the name}
#
# Returns the slave name.
#
# Optional Arguments : 
# + slave name : if empty, generated name will be used
# + access_path: path list controlling where load/source can occur,
#                if empty: the master auto_path will be used.
# + staticsok  : flag, if 0 :no static package can be loaded (load {} Xxx)
#                      if 1 :static packages are ok.
# + nestedok: flag, if 0 :no loading to sub-sub interps (load xx xx sub)
#                      if 1 : multiple levels are ok.

# use the full name and no indent so auto_mkIndex can find us
proc ::safe::InterpCreate {
                           slave 
                           access_path
                           staticsok
                           nestedok
                           deletehook
                       } {
    # Create the slave.
    if {$slave ne ""} {
        ::interp create -safe $slave
    } else {
        # empty argument: generate slave name
        set slave [::interp create -safe]
    }
    Log $slave "Created" NOTICE

    # Initialize it. (returns slave name)
    InterpInit $slave $access_path $staticsok $nestedok $deletehook
}

#
# InterpSetConfig (was setAccessPath) :
#    Sets up slave virtual auto_path and corresponding structure within
#    the master. Also sets the tcl_library in the slave to be the first
#    directory in the path.
#    NB: If you change the path after the slave has been initialized you
#    probably need to call "auto_reset" in the slave in order that it gets
#    the right auto_index() array values.

proc ::safe::InterpSetConfig {slave access_path staticsok nestedok deletehook} {
    global auto_path

    # determine and store the access path if empty
    if {$access_path eq ""} {
        set access_path $auto_path

        # Make sure that tcl_library is in auto_path and at the first
        # position (needed by setAccessPath)
        set where [lsearch -exact $access_path [info library]]
        if {$where == -1} {
            # not found, add it.
            set access_path [linsert $access_path 0 [info library]]
            Log $slave "tcl_library was not in auto_path,\
                        added it to slave's access_path" NOTICE
        } elseif {$where != 0} {
            # not first, move it first
            set access_path [linsert \
                                 [lreplace $access_path $where $where] \
                                 0 [info library]]
            Log $slave "tcl_libray was not in first in auto_path,\
                        moved it to front of slave's access_path" NOTICE
        }

        # Add 1st level sub dirs (will searched by auto loading from tcl
        # code in the slave using glob and thus fail, so we add them here
        # so by default it works the same).
        set access_path [AddSubDirs $access_path]
    }

    Log $slave "Setting accessPath=($access_path) staticsok=$staticsok\
                nestedok=$nestedok deletehook=($deletehook)" NOTICE

    namespace upvar ::safe S$slave state

    # clear old autopath if it existed
    # build new one
    # Extend the access list with the paths used to look for Tcl Modules.
    # We save the virtual form separately as well, as syncing it with the
    # slave has to be defered until the necessary commands are present for
    # setup.

    set norm_access_path  {}
    set slave_access_path {}
    set map_access_path   {}
    set remap_access_path {}
    set slave_tm_path     {}

    set i 0
    foreach dir $access_path {
        set token [PathToken $i]
        lappend slave_access_path  $token
        lappend map_access_path    $token $dir
        lappend remap_access_path  $dir $token
        lappend norm_access_path   [file normalize $dir]
        incr i
    }

    set morepaths [::tcl::tm::list]
    while {[llength $morepaths]} {
        set addpaths $morepaths
        set morepaths {}

        foreach dir $addpaths {
            # Prevent the addition of dirs on the tm list to the
            # result if they are already known.
            if {[dict exists $remap_access_path $dir]} {
                continue
            }

            set token [PathToken $i]
            lappend access_path        $dir
            lappend slave_access_path  $token
            lappend map_access_path    $token $dir
            lappend remap_access_path  $dir $token
            lappend norm_access_path   [file normalize $dir]
            lappend slave_tm_path $token
            incr i

            # [Bug 2854929]
            # Recursively find deeper paths which may contain
            # modules. Required to handle modules with names like
            # 'platform::shell', which translate into
            # 'platform/shell-X.tm', i.e arbitrarily deep
            # subdirectories.
            lappend morepaths {*}[glob -nocomplain -directory $dir -type d *]
        }
    }

    set state(access_path)       $access_path
    set state(access_path,map)   $map_access_path
    set state(access_path,remap) $remap_access_path
    set state(access_path,norm)  $norm_access_path
    set state(access_path,slave) $slave_access_path
    set state(tm_path_slave)     $slave_tm_path
    set state(staticsok)         $staticsok
    set state(nestedok)          $nestedok
    set state(cleanupHook)       $deletehook

    SyncAccessPath $slave
}

#
#
# FindInAccessPath:
#    Search for a real directory and returns its virtual Id (including the
#    "$")
proc ::safe::interpFindInAccessPath {slave path} {
    namespace upvar ::safe S$slave state

    if {![dict exists $state(access_path,remap) $path]} {
        return -code error "$path not found in access path $access_path"
    }

    return [dict get $state(access_path,remap) $path]
}

#
# addToAccessPath:
#    add (if needed) a real directory to access path and return its
#    virtual token (including the "$").
proc ::safe::interpAddToAccessPath {slave path} {
    # first check if the directory is already in there
    # (inlined interpFindInAccessPath).
    namespace upvar ::safe S$slave state

    if {[dict exists $state(access_path,remap) $path]} {
        return [dict get $state(access_path,remap) $path]
    }

    # new one, add it:
    set token [PathToken [llength $state(access_path)]]

    lappend state(access_path)       $path
    lappend state(access_path,slave) $token
    lappend state(access_path,map)   $token $path
    lappend state(access_path,remap) $path $token
    lappend state(access_path,norm)  [file normalize $path]

    SyncAccessPath $slave
    return $token
}

# This procedure applies the initializations to an already existing
# interpreter. It is useful when you want to install the safe base aliases
# into a preexisting safe interpreter.
proc ::safe::InterpInit {
                         slave 
                         access_path
                         staticsok
                         nestedok
                         deletehook
                     } {
    # Configure will generate an access_path when access_path is empty.
    InterpSetConfig $slave $access_path $staticsok $nestedok $deletehook

    # NB we need to add [namespace current], aliases are always absolute
    # paths.

    # These aliases let the slave load files to define new commands
    # This alias lets the slave use the encoding names, convertfrom,
    # convertto, and system, but not "encoding system <name>" to set the
    # system encoding.
    # Handling Tcl Modules, we need a restricted form of Glob.
    # This alias interposes on the 'exit' command and cleanly terminates
    # the slave.

    foreach {command alias} {
        source   AliasSource
        load     AliasLoad
        encoding AliasEncoding
        exit     interpDelete
        glob     AliasGlob
    } {
        ::interp alias $slave $command {} [namespace current]::$alias $slave
    }

    # This alias lets the slave have access to a subset of the 'file'
    # command functionality.

    AliasSubset $slave file \
        file  dir.* join root.* ext.* tail path.* split

    # Subcommands of info
    foreach {subcommand alias} {
        nameofexecutable   AliasExeName
    } {
        ::interp alias $slave ::tcl::info::$subcommand \
            {} [namespace current]::$alias $slave
    }

    # The allowed slave variables already have been set by Tcl_MakeSafe(3)

    # Source init.tcl and tm.tcl into the slave, to get auto_load and
    # other procedures defined:

    if {[catch {::interp eval $slave {
        source [file join $tcl_library init.tcl]
    }} msg]} {
        Log $slave "can't source init.tcl ($msg)"
        return -code error "can't source init.tcl into slave $slave ($msg)"
    }

    if {[catch {::interp eval $slave {
        source [file join $tcl_library tm.tcl]
    }} msg]} {
        Log $slave "can't source tm.tcl ($msg)"
        return -code error "can't source tm.tcl into slave $slave ($msg)"
    }

    # Sync the paths used to search for Tcl modules. This can be done only
    # now, after tm.tcl was loaded.
    namespace upvar ::safe S$slave state
    ::interp eval $slave [list \
              ::tcl::tm::add {*}$state(tm_path_slave)]

    return $slave
}

# Add (only if needed, avoid duplicates) 1 level of sub directories to an
# existing path list.  Also removes non directories from the returned
# list.
proc ::safe::AddSubDirs {pathList} {
    set res {}
    foreach dir $pathList {
        if {[file isdirectory $dir]} {
            # check that we don't have it yet as a children of a previous
            # dir
            if {$dir ni $res} {
                lappend res $dir
            }
            foreach sub [glob -directory $dir -nocomplain *] {
                if {[file isdirectory $sub] && ($sub ni $res)} {
                    # new sub dir, add it !
                    lappend res $sub
                }
            }
        }
    }
    return $res
}

# This procedure deletes a safe slave managed by Safe Tcl and cleans up
# associated state:

proc ::safe::interpDelete {slave} {
    Log $slave "About to delete" NOTICE

    namespace upvar ::safe S$slave state

    # If the slave has a cleanup hook registered, call it.  Check the
    # existance because we might be called to delete an interp which has
    # not been registered with us at all

    if {[info exists state(cleanupHook)]} {
        set hook $state(cleanupHook)
        if {[llength $hook]} {
            # remove the hook now, otherwise if the hook calls us somehow,
            # we'll loop
            unset state(cleanupHook)
            if {[catch {
                {*}$hook $slave
            } err]} {
                Log $slave "Delete hook error ($err)"
            }
        }
    }

    # Discard the global array of state associated with the slave, and
    # delete the interpreter.

    if {[info exists state]} {
        unset state
    }

    # if we have been called twice, the interp might have been deleted
    # already
    if {[::interp exists $slave]} {
        ::interp delete $slave
        Log $slave "Deleted" NOTICE
    }

    return
}

# Set (or get) the logging mecanism 

proc ::safe::setLogCmd {args} {
    variable Log
    set la [llength $args]
    if {$la == 0} {
        return $Log
    } elseif {$la == 1} {
        set Log [lindex $args 0]
    } else {
        set Log $args
    }

    if {$Log eq ""} {
        # Disable logging completely. Calls to it will be compiled out
        # of all users.
        proc ::safe::Log {args} {}
    } else {
        # Activate logging, define proper command.

        proc ::safe::Log {slave msg {type ERROR}} {
            variable Log
            {*}$Log "$type for slave $slave : $msg"
            return
        }
    }
}

# ------------------- END OF PUBLIC METHODS ------------

#
# Sets the slave auto_path to the master recorded value.  Also sets
# tcl_library to the first token of the virtual path.
#
proc ::safe::SyncAccessPath {slave} {
    namespace upvar ::safe S$slave state

    set slave_access_path $state(access_path,slave)
    ::interp eval $slave [list set auto_path $slave_access_path]

    Log $slave "auto_path in $slave has been set to $slave_access_path"\
        NOTICE

    # This code assumes that info library is the first element in the
    # list of auto_path's. See -> InterpSetConfig for the code which
    # ensures this condition.

    ::interp eval $slave [list \
              set tcl_library [lindex $slave_access_path 0]]
}

# Returns the virtual token for directory number N.
proc ::safe::PathToken {n} {
    # We need to have a ":" in the token string so [file join] on the
    # mac won't turn it into a relative path.
    return "\$p(:$n:)" ;# Form tested by case 7.2
}

#
# translate virtual path into real path
#
proc ::safe::TranslatePath {slave path} {
    namespace upvar ::safe S$slave state

    # somehow strip the namespaces 'functionality' out (the danger is that
    # we would strip valid macintosh "../" queries... :
    if {[string match "*::*" $path] || [string match "*..*" $path]} {
        return -code error "invalid characters in path $path"
    }

    # Use a cached map instead of computed local vars and subst.

    return [string map $state(access_path,map) $path]
}

# file name control (limit access to files/resources that should be a
# valid tcl source file)
proc ::safe::CheckFileName {slave file} {
    # This used to limit what can be sourced to ".tcl" and forbid files
    # with more than 1 dot and longer than 14 chars, but I changed that
    # for 8.4 as a safe interp has enough internal protection already to
    # allow sourcing anything. - hobbs

    if {![file exists $file]} {
        # don't tell the file path
        return -code error "no such file or directory"
    }

    if {![file readable $file]} {
        # don't tell the file path
        return -code error "not readable"
    }
}

# AliasGlob is the target of the "glob" alias in safe interpreters.
proc ::safe::AliasGlob {slave args} {
    Log $slave "GLOB ! $args" NOTICE
    set cmd {}
    set at 0
    array set got {
        -directory 0
        -nocomplain 0
        -join 0
        -tails 0
        -- 0
    }

    if {$::tcl_platform(platform) eq "windows"} {
        set dirPartRE {^(.*)[\\/]}
    } else {
        set dirPartRE {^(.*)/}
    }

    set dir        {}
    set virtualdir {}

    while {$at < [llength $args]} {
        switch -glob -- [set opt [lindex $args $at]] {
            -nocomplain - -- - -join - -tails {
                lappend cmd $opt
                set got($opt) 1
                incr at
            }
            -types - -type {
                lappend cmd -types [lindex $args [incr at]]
                incr at
            }
            -directory {
                if {$got($opt)} {
                    return -code error \
                        {"-directory" cannot be used with "-path"}
                }
                set got($opt) 1
                set virtualdir [lindex $args [incr at]]
                incr at
            }
            pkgIndex.tcl {
                # Oops, this is globbing a subdirectory in regular package
                # search. That is not wanted. Abort, handler does catch
                # already (because glob was not defined before). See
                # package.tcl, lines 484ff in tclPkgUnknown.
                return -code error "unknown command glob"
            }
            -* {
                Log $slave "Safe base rejecting glob option '$opt'"
                return -code error "Safe base rejecting glob option '$opt'"
            }
            default {
                break
            }
        }
        if {$got(--)} break
    }

    # Get the real path from the virtual one and check that the path is in the
    # access path of that slave. Done after basic argument processing so that
    # we know if -nocomplain is set.
    if {$got(-directory)} {
        if {[catch {
            set dir [TranslatePath $slave $virtualdir]
            DirInAccessPath $slave $dir
        } msg]} {
            Log $slave $msg
            if {!$got(-nocomplain)} {
                return -code error "permission denied"
            } else {
                return
            }
        }
        lappend cmd -directory $dir
    }

    # Apply the -join semantics ourselves
    if {$got(-join)} {
        set args [lreplace $args $at end [join [lrange $args $at end] "/"]]
    }

    # Process remaining pattern arguments
    set firstPattern [llength $cmd]
    while {$at < [llength $args]} {
        set opt [lindex $args $at]
        incr at
        if {[regexp $dirPartRE $opt -> thedir] && [catch {
            set thedir [file join $virtualdir $thedir]
            DirInAccessPath $slave [TranslatePath $slave $thedir]
        } msg]} {
            Log $slave $msg
            if {$got(-nocomplain)} {
                continue
            } else {
                return -code error "permission denied"
            }
        }
        lappend cmd $opt
    }

    Log $slave "GLOB = $cmd" NOTICE

    if {$got(-nocomplain) && [llength $cmd] eq $firstPattern} {
        return
    }
    if {[catch {
        ::interp invokehidden $slave glob {*}$cmd
    } msg]} {
        Log $slave $msg
        return -code error "script error"
    }

    Log $slave "GLOB @ $msg" NOTICE

    # Translate path back to what the slave should see.
    set res {}
    set l [string length $dir]
    foreach p $msg {
        if {[string equal -length $l $dir $p]} {
            set p [string replace $p 0 [expr {$l-1}] $virtualdir]
        }
        lappend res $p
    }

    Log $slave "GLOB @ $res" NOTICE
    return $res
}

# AliasSource is the target of the "source" alias in safe interpreters.

proc ::safe::AliasSource {slave args} {
    set argc [llength $args]
    # Extended for handling of Tcl Modules to allow not only "source
    # filename", but "source -encoding E filename" as well.
    if {[lindex $args 0] eq "-encoding"} {
        incr argc -2
        set encoding [lindex $args 1]
        set at 2
        if {$encoding eq "identity"} {
            Log $slave "attempt to use the identity encoding"
            return -code error "permission denied"
        }
    } else {
        set at 0
        set encoding {}
    }
    if {$argc != 1} {
        set msg "wrong # args: should be \"source ?-encoding E? fileName\""
        Log $slave "$msg ($args)"
        return -code error $msg
    }
    set file [lindex $args $at]
    
    # get the real path from the virtual one.
    if {[catch {
        set realfile [TranslatePath $slave $file]
    } msg]} {
        Log $slave $msg
        return -code error "permission denied"
    }
    
    # check that the path is in the access path of that slave
    if {[catch {
        FileInAccessPath $slave $realfile
    } msg]} {
        Log $slave $msg
        return -code error "permission denied"
    }

    # do the checks on the filename :
    if {[catch {
        CheckFileName $slave $realfile
    } msg]} {
        Log $slave "$realfile:$msg"
        return -code error $msg
    }

    # Passed all the tests, lets source it. Note that we do this all manually
    # because we want to control [info script] in the slave so information
    # doesn't leak so much. [Bug 2913625]
    set old [::interp eval $slave {info script}]
    set code [catch {
        set f [open $realfile]
        fconfigure $f -eofchar \032
        if {$encoding ne ""} {
            fconfigure $f -encoding $encoding
        }
        set contents [read $f]
        close $f
        ::interp eval $slave [list info script $file]
        ::interp eval $slave $contents
    } msg opt]
    catch {interp eval $slave [list info script $old]}
    # Note that all non-errors are fine result codes from [source], so we must
    # take a little care to do it properly. [Bug 2923613]
    if {$code == 1} {
        Log $slave $msg
        return -code error "script error"
    }
    return -code $code -options $opt $msg
}

# AliasLoad is the target of the "load" alias in safe interpreters.

proc ::safe::AliasLoad {slave file args} {
    set argc [llength $args]
    if {$argc > 2} {
        set msg "load error: too many arguments"
        Log $slave "$msg ($argc) {$file $args}"
        return -code error $msg
    }

    # package name (can be empty if file is not).
    set package [lindex $args 0]

    namespace upvar ::safe S$slave state

    # Determine where to load. load use a relative interp path and {}
    # means self, so we can directly and safely use passed arg.
    set target [lindex $args 1]
    if {$target ne ""} {
        # we will try to load into a sub sub interp; check that we want to
        # authorize that.
        if {!$state(nestedok)} {
            Log $slave "loading to a sub interp (nestedok)\
                        disabled (trying to load $package to $target)"
            return -code error "permission denied (nested load)"
        }
    }

    # Determine what kind of load is requested
    if {$file eq ""} {
        # static package loading
        if {$package eq ""} {
            set msg "load error: empty filename and no package name"
            Log $slave $msg
            return -code error $msg
        }
        if {!$state(staticsok)} {
            Log $slave "static packages loading disabled\
                        (trying to load $package to $target)"
            return -code error "permission denied (static package)"
        }
    } else {
        # file loading

        # get the real path from the virtual one.
        if {[catch {
            set file [TranslatePath $slave $file]
        } msg]} {
            Log $slave $msg
            return -code error "permission denied"
        }

        # check the translated path
        if {[catch {
            FileInAccessPath $slave $file
        } msg]} {
            Log $slave $msg
            return -code error "permission denied (path)"
        }
    }

    if {[catch {
        ::interp invokehidden $slave load $file $package $target
    } msg]} {
        Log $slave $msg
        return -code error $msg
    }

    return $msg
}

# FileInAccessPath raises an error if the file is not found in the list of
# directories contained in the (master side recorded) slave's access path.

# the security here relies on "file dirname" answering the proper
# result... needs checking ?
proc ::safe::FileInAccessPath {slave file} {
    namespace upvar ::safe S$slave state
    set access_path $state(access_path)

    if {[file isdirectory $file]} {
        return -code error "\"$file\": is a directory"
    }
    set parent [file dirname $file]

    # Normalize paths for comparison since lsearch knows nothing of
    # potential pathname anomalies.
    set norm_parent [file normalize $parent]

    namespace upvar ::safe S$slave state
    if {$norm_parent ni $state(access_path,norm)} {
        return -code error "\"$file\": not in access_path"
    }
}

proc ::safe::DirInAccessPath {slave dir} {
    namespace upvar ::safe S$slave state
    set access_path $state(access_path)

    if {[file isfile $dir]} {
        return -code error "\"$dir\": is a file"
    }

    # Normalize paths for comparison since lsearch knows nothing of
    # potential pathname anomalies.
    set norm_dir [file normalize $dir]

    namespace upvar ::safe S$slave state
    if {$norm_dir ni $state(access_path,norm)} {
        return -code error "\"$dir\": not in access_path"
    }
}

# This procedure enables access from a safe interpreter to only a subset
# of the subcommands of a command:

proc ::safe::Subset {slave command okpat args} {
    set subcommand [lindex $args 0]
    if {[regexp $okpat $subcommand]} {
        return [$command {*}$args]
    }
    set msg "not allowed to invoke subcommand $subcommand of $command"
    Log $slave $msg
    return -code error $msg
}

# This procedure installs an alias in a slave that invokes "safesubset" in
# the master to execute allowed subcommands. It precomputes the pattern of
# allowed subcommands; you can use wildcards in the pattern if you wish to
# allow subcommand abbreviation.
#
# Syntax is: AliasSubset slave alias target subcommand1 subcommand2...

proc ::safe::AliasSubset {slave alias target args} {
    set pat "^([join $args |])\$"
    ::interp alias $slave $alias {}\
        [namespace current]::Subset $slave $target $pat
}

# AliasEncoding is the target of the "encoding" alias in safe interpreters.

proc ::safe::AliasEncoding {slave option args} {
    # Careful; do not want empty option to get through to the [string equal]
    if {[regexp {^(name.*|convert.*|)$} $option]} {
        return [::interp invokehidden $slave encoding $option {*}$args]
    }

    if {[string equal -length [string length $option] $option "system"]} {
        if {[llength $args] == 0} {
            # passed all the tests , lets source it:
            if {[catch {
                set sysenc [::interp invokehidden $slave encoding system]
            } msg]} {
                Log $slave $msg
                return -code error "script error"
            }
            return $sysenc
        }
        set msg "wrong # args: should be \"encoding system\""
        set code {TCL WRONGARGS}
    } else {
        set msg "bad option \"$option\": must be convertfrom, convertto, names, or system"
        set code [list TCL LOOKUP INDEX option $option]
    }
    Log $slave $msg
    return -code error -errorcode $code $msg
}

# Various minor hiding of platform features. [Bug 2913625]

proc ::safe::AliasExeName {slave} {
    return ""
}

proc ::safe::Setup {} {
    ####
    #
    # Setup the arguments parsing
    #
    ####

    # Share the descriptions
    set temp [::tcl::OptKeyRegister {
        {-accessPath -list {} "access path for the slave"}
        {-noStatics "prevent loading of statically linked pkgs"}
        {-statics true "loading of statically linked pkgs"}
        {-nestedLoadOk "allow nested loading"}
        {-nested false "nested loading"}
        {-deleteHook -script {} "delete hook"}
    }]

    # create case (slave is optional)
    ::tcl::OptKeyRegister {
        {?slave? -name {} "name of the slave (optional)"}
    } ::safe::interpCreate

    # adding the flags sub programs to the command program (relying on Opt's
    # internal implementation details)
    lappend ::tcl::OptDesc(::safe::interpCreate) $::tcl::OptDesc($temp)

    # init and configure (slave is needed)
    ::tcl::OptKeyRegister {
        {slave -name {} "name of the slave"}
    } ::safe::interpIC

    # adding the flags sub programs to the command program (relying on Opt's
    # internal implementation details)
    lappend ::tcl::OptDesc(::safe::interpIC) $::tcl::OptDesc($temp)

    # temp not needed anymore
    ::tcl::OptKeyDelete $temp

    ####
    #
    # Default: No logging.
    #
    ####

    setLogCmd {}

    # Log eventually.
    # To enable error logging, set Log to {puts stderr} for instance,
    # via setLogCmd.
    return
}

namespace eval ::safe {
    # internal variables

    # Log command, set via 'setLogCmd'. Logging is disabled when empty.
    variable Log {}

    # The package maintains a state array per slave interp under its
    # control. The name of this array is S<interp-name>. This array is
    # brought into scope where needed, using 'namespace upvar'. The S
    # prefix is used to avoid that a slave interp called "Log" smashes
    # the "Log" variable.
    #
    # The array's elements are:
    #
    # access_path       : List of paths accessible to the slave.
    # access_path,norm  : Ditto, in normalized form.
    # access_path,slave : Ditto, as the path tokens as seen by the slave.
    # access_path,map   : dict ( token -> path )
    # access_path,remap : dict ( path -> token )
    # tm_path_slave     : List of TM root directories, as tokens seen by the slave.
    # staticsok         : Value of option -statics
    # nestedok          : Value of option -nested
    # cleanupHook       : Value of option -deleteHook
}

::safe::Setup