fconfigure $f -buffersize 100000
    lappend l [fconfigure $f -buffersize]
    fconfigure $f -buffersize 10000000
    lappend l [fconfigure $f -buffersize]
    close $f
    set l
} {4096 10000 1 1 1 100000 1048576}
test io-38.3 {Tcl_SetChannelBufferSize, changing buffersize between reads} knownBug {
    # This test crashes the interp if Bug #427196 is not fixed

    set chan [open [info script] r]
    fconfigure $chan -buffersize 10
    set var [read $chan 2]
    fconfigure $chan -buffersize 32
    append var [read $chan]

    variable fcopyTestDone
    if {[string length $error]} {
	set fcopyTestDone 1
    } else {
	set fcopyTestDone 0
    }
}
test io-53.5 {CopyData: error during fcopy} {socket fcopy knownBug} {
    variable fcopyTestDone
    set listen [socket -server [namespace code FcopyTestAccept] -myaddr 127.0.0.1 0]
    set in [open $thisScript]	;# 126 K
    set out [socket 127.0.0.1 [lindex [fconfigure $listen -sockname] 2]]
    catch {unset fcopyTestDone}
    close $listen	;# This means the socket open never really succeeds
    fcopy $in $out -command [namespace code FcopyTestDone]

    lappend hd [catch {read $f} msg]
    close $f
    lappend hd $msg
} -cleanup {
    removeFile io-75.6
} -match glob -result {41 1 {error reading "*": illegal byte sequence}}

test io-75.7 {invalid utf-8 encoding eof handling} -constraints knownBug -setup {
    set fn [makeFile {} io-75.7]
    set f [open $fn w+]
    fconfigure $f -encoding binary
    # \xA1 is invalid in utf-8. -eofchar is not detected, because it comes later.
    puts -nonewline $f A\xA1\x1A
    flush $f
    seek $f 0