src/cmd/ksh93/tests/readonly.sh:
- Use a 'ulimit --cpu' as a workaround to close down hung processes
that might be caused due to a couple of known bugs (recursion and
type variable function)
Discussion: https://github.com/ksh93/ksh/issues/264
- Adjust tests so xtrace can be used
- Use integer n within for loop
One area where readonly is still ineffective is the local
environment list for a command (preceding assignments) if that
command is not executed using exec(3) after fork(2). Builtin
commands are one example. The following succeeds but should fail:
(readonly v=1; v=2 true) # succeeds, but should fail
If the shell is compiled with SHOPT_SPAWN (the default) then this
also applies to external commands invoked with sh_ntfork():
(readonly v=1; v=2 env) # succeeds if SHOPT_SPAWN
This presents to the user as inconsitent behaviour because external
commands may be fork()ed under certain circumstances but not
others, depending on complex optimisations. One example is:
$ ksh -c 'readonly v=1; v=2 env'
ksh: v: is read only
$ ksh -c 'readonly v=1; v=2 env; :'
(bad: environment list is output, including 'v=2')
In the first command above, where 'v2=env' is the last command in
the -c script, the optimisation skips creating a scope and assigns
the environment list in the current scope.
src/cmd/ksh93/sh/name.c: nv_setlist():
- Add check for readonly. This requires searching for the variable
in the main tree using nv_search() before a locally scoped one is
added using nv_open(). Since nv_search() only works with plain
variable names, temporarily end the string at '='.
src/cmd/ksh93/tests/readonly.sh:
- Add version check and fork the test command substitution subshell
on older versions that would otherwise abort the tests due to the
combination of an excessively low arithmetic recursion tolerance
and a bug that sometimes fails to restore the shell's arithmetic
recursion level.
$ /usr/local/bin/ksh -c 'readonly v=1; export v'
/usr/local/bin/ksh: export: v: is read only
Every POSIX shell (even zsh, as of 5.8) allows this. So did ksh,
until the referenced commit.
src/cmd/ksh93/bltins/typeset.c: setall():
- Allow setting attributes on a readonly variable if any of
NV_ASSIGN (== NV_NOFREE), NV_EXPORT or NV_RDONLY are the only
flag bits that are set. This allows readonly, export, typeset -r,
typeset -x, and typeset -rx on variable arguments without an
assignment. Note that NV_ASSIGN is set for the first variable
argument even though it is not an assignment, so we must allow
it. The logic (or lack thereof) of that is yet to be worked out.
src/cmd/ksh93/tests/readonly.sh:
- Tests.
Resolves: https://github.com/ksh93/ksh/issues/258
Ksh currently restricts readonly scalar variables from having their
values directly changed via a value assignment. However, since ksh
allows variable attributes to be altered, the variable's value can
be indirectly altered. For instance, if TMOUT=900 (for a 15 minute
idle timeout) was set to readonly, all that is needed to alter the
value of TMOUT from 900 to 0 is to issue 'typeset -R1 TMOUT',
perhaps followed by a 'typeset -i TMOUT' to turn off the shell's
timeout value.
In addition, there are problems with arrays. The following is
incorrectly allowed:
typeset -a arr=((a b c) 1)
readonly arr
arr[0][1]=d
arr=(alphas=(a b c);name=x)
readonly arr.alphas
arr.alphas[1]=([b]=5)
arr=(alphas=(a b c);name=x)
readonly arr.alphas
arr.alphas[1]=(b)
typeset -C arr=(typeset -r -a alphas=(a b c);name=x)
arr.alphas[1]=()
src/cmd/ksh93/bltins/typeset.c: setall():
- Relocate readonly attribute check higher up the code and widen
its application to issue an error message if the pre-existing
name-pair has the readonly bit flag set.
- To avoid compatibility problems, don't check for readonly if
NV_RDONLY is the only attribute set (ignoring NV_NOFREE). This
allows 'readonly foo; readonly foo' to keep working.
src/cmd/ksh93/sh/array.c: nv_endsubscript():
- Apply a readonly flag check when an array subscript or append
assignment occurs, but allow type variables (typeset -T) as they
utilize '-r' for 'required' sub-variables.
src/cmd/ksh93/tests/readonly.sh:
- New file. Create readonly tests that validate the warning message
and validate that the readonly variable did not change.
src/cmd/ksh93/sh/streval.c:
- Bump MAXLEVEL from 9 to 1024 as a workaround for arithmetic
expansion, avoiding a spurious error about too much recursion
when the readonly.sh tests are run. This change is backported
from ksh 93v-.
TODO: debug a spurious increase in arithmetic recursion level
variable when readonly.sh tests with 'typeset -i' are run.
That is a different bug for a different commit.
Co-authored-by: Martijn Dekker <martijn@inlv.org>
