Evaluation of commands goes completely haywire if a file containing
a break/continue/return command outside its "intended" scope is sourced
using a dot command inside its "intended" scope. The main symptom is
not exiting from the sourced file when supposed to, leading to evaluation
of commands that were not supposed to be evaluated. A secondary symptom
is that these extra commands are not evaluated correctly, as some of them
are skipped. Some examples are listed in the How-To-Repeat section.
According to the POSIX standard, this is how it should work:
dot:
The shell shall execute commands from the file in the current
environment.
break:
The break utility shall exit from the smallest enclosing for, while,
or until loop, [...]
continue:
The continue utility shall return to the top of the smallest
enclosing for, while, or until loop, [...]
return:
The return utility shall cause the shell to stop executing
the current function or dot script. If the shell is not currently
executing a function or dot script, the results are unspecified.
It is clear that return should return from a sourced file, which
it does not do. Whether break and continue should work from the sourced
file might be debatable. Because the dot command says "in the current
environment", I'd say yes. In any case, it should not fail in weird
ways like it does now!
The problems occur with return (a) and break/continue (b) because:
1) dotcmd() does not record the function nesting level prior to
sourcing the file nor does it touch the loopnest variable,
leading to either
2 a) returncmd() being unable to detect that it should not set
evalskip to SKIPFUNC but SKIPFILE, or
b) breakcmd() setting evalskip to SKIPCONT or SKIPBREAK,
leading to
3) cmdloop() not detecting that it should skip the rest of
the file, due to only checking for SKIPFILE.
The result is that cmdloop() keeps executing lines from the file
whilst evalskip is set, which is the main symptom. Because
evalskip is checked in multiple places in eval.c, the secondary
symptom appears.
>How-To-Repeat:
Run the following script:
printf "break\necho break1; echo break2" >break
printf "continue\necho continue1; echo continue2" >continue
printf "return\necho return1; echo return2" >return
while true; do . ./break; done
for i in 1 2; do . ./continue; done
func() {
. ./return
}
func
No output should be produced, but instead this is the result:
break1
continue1
continue1
return1
The main symptom is evident from the unexpected output and the secondary
one from the fact that there are no lines with '2' in them.
>Fix:
Here is patch to src/bin/sh to fix the above problems. It keeps
track of the function nesting level at the beginning of a dot command
to enable the return command to work properly.
I also changed the undefined-by-standard functionality of the return
command when it's not in a dot command or function from (indirectly)
exiting the shell to being silently ignored. This was done because
the previous way has at least one bug: the shell exits without asking
for confirmation when there are stopped jobs.
Because I read the standard to mean that break and continue should have
an effect outside the sourced file, that's how I implemented it. For what
it's worth, this also seems to be what bash does. Also laziness, because
this way required no changes to loopnesting tracking. If this is not
wanted, it might make sense to move the nesting tracking to the inputfile
stack.
The patch also does some clean-up to reduce the amount of global
variables by moving the dotcmd() and the find_dot_file() functions from
main.c to eval.c and making in_function() a proper function.
We have written a diff to our ls(1) to recover the traditional behaviour
of -f implying -a. This change does not only accommodates POSIX.1
but also matches traditional UNIX.
OpenBSD commit message:
CVSROOT: /cvs
Module name: src
Changes by: sobrado@cvs.openbsd.org 2014/03/31 14:54:37
Modified files:
bin/ls : ls.1 ls.c
Log message:
restore the traditional behavior of -f implying -a; apparently Keith Bostic
forgot to restore it when the -f flag was put back on 2nd of September 1989,
after being removed on 16th of August as a consequence of issues getting it
working over NFS, so deviation from traditional UNIX behavior in all BSDs
looks like an historical accident; as a side effect, this change accommodates
behavior of this option to IEEE Std 1003.1-2008 (``POSIX.1'').
joint work with jmc@ (who found the inaccuracy in our implementation),
schwarze@ (who provided a detailed tracking of historical facts) and millert@
ok millert@, schwarze@
The -H, -L and -P options are ignored unless the -R option is
specified. In addition, these options override each other and the
command's actions are determined by the last one specified.
Add:
The default is as if the -P option had been specified.
bin/cat/cat.c 976654 Argument cannot be negative
(missing check for fileno result, stdout)
bin/cat/cat.c 976653 Improper use of negative value
(missing check for fileno result, stdin)
sh +nounset and `for X; do` iteration fails if parameter set empty
by applying and testing FreeBSD's patch of Oct 24 2009 for this; see
http://svnweb.freebsd.org/base/head/bin/sh/expand.c?r1=198453&r2=198454
Also created an ATF test in tests/bin/sh/t_expand.sh for this error and
corrected a space->tabs problem there as well.
XXX: someone should fix all the .Ev stuff because some of them are just
shell variables .Va and are not really exported to the environment. See
the FreeBSD man page.
-A Display the FQDN of each address on all interfaces.
-a Display alias name(s) of the host.
-d Display the DNS domain.
-f Display the FQDN for the hostname.
-I Display each IP address on all interfaces.
-i Display the IP address(es) for the hostname.
christos