Date: Tue, 28 Dec 2010 21:27:08 +0000 (UTC) From: Jilles Tjoelker <jilles@FreeBSD.org> To: cvs-src-old@freebsd.org Subject: cvs commit: src/bin/sh eval.c expand.c expand.h src/tools/regression/bin/sh/expansion cmdsubst7.0 Message-ID: <201012282129.oBSLToRH075132@repoman.freebsd.org>
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jilles 2010-12-28 21:27:08 UTC
FreeBSD src repository
Modified files:
bin/sh eval.c expand.c expand.h
Added files:
tools/regression/bin/sh/expansion cmdsubst7.0
Log:
SVN rev 216778 on 2010-12-28 21:27:08Z by jilles
sh: Don't do optimized command substitution if expansions have side effects.
Before considering to execute a command substitution in the same process,
check if any of the expansions may have a side effect; if so, execute it in
a new process just like happens if it is not a single simple command.
Although the check happens at run time, it is a static check that does not
depend on current state. It is triggered by:
- expanding $! (which may cause the job to be remembered)
- ${var=value} default value assignment
- assignment operators in arithmetic
- parameter substitutions in arithmetic except ${#param}, $$, $# and $?
- command substitutions in arithmetic
This means that $((v+1)) does not prevent optimized command substitution,
whereas $(($v+1)) does, because $v might expand to something containing
assignment operators.
Scripts should not depend on these exact details for correctness. It is also
imaginable to have the shell fork if and when a side effect is encountered
or to create a new temporary namespace for variables.
Due to the $! change, the construct $(jobs $!) no longer works. The value of
$! should be stored in a variable outside command substitution first.
Revision Changes Path
1.96 +15 -1 src/bin/sh/eval.c
1.81 +72 -0 src/bin/sh/expand.c
1.15 +1 -0 src/bin/sh/expand.h
1.1 +31 -0 src/tools/regression/bin/sh/expansion/cmdsubst7.0 (new)
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