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a2196f9434
ksh93 currently has three command substitution mechanisms:
- type 1: old-style backtick comsubs that use a pipe;
- type 3: $(modern) comsubs that use a temp file, currently with
fallback to a pipe if a temp file cannot be created;
- type 2: ${ shared-state; } comsubs; same as type 3, but shares
state with parent environment.
Type 1 is buggy. There are at least two reproducers that make it
hang. The Red Hat patch applied in 4ce486a7 fixed a hang in
backtick comsubs but reintroduced another hang that was fixed in
ksh 93v-. So far, no one has succeeded in making pipe-based comsubs
work properly.
But, modern (type 3) comsubs use temp files. How does it make any
sense to have two different command substitution mechanisms at the
execution level? The specified functionality between backtick and
modern command substitutions is exactly the same; the difference
*should* be purely syntactic.
So this commit removes the type 1 comsub code at the execution
level, treating them all like type 3 (or 2). As a result, the
related bugs vanish while the regression tests all pass.
The only side effect that I can find is that the behaviour of bug
https://github.com/ksh93/ksh/issues/124 changes for backtick
comsubs. But it's broken either way, so that's neutral.
So this commit can now be added to my growing list of ksh93 issues
fixed by simply removing code.
src/cmd/ksh93/sh/xec.c:
- Remove special code for type 1 comsubs from iousepipe(),
sh_iounpipe(), sh_exec() and _sh_fork().
src/cmd/ksh93/include/defs.h,
src/cmd/ksh93/sh/subshell.c:
- Remove pipe support from sh_subtmpfile(). This also removes the
use of a pipe as a fallback for $(modern) comsubs. Instead, panic
and error out if temp file creation fails. If the shell cannot
create a temporary file, there are fatal system problems anyway
and a script should not continue.
- No longer pass comsub type to sh_subtmpfile().
All other changes:
- Update sh_subtmpfile() calls.
src/cmd/ksh93/tests/subshell.sh:
- Add two regression tests based on reproducers from bug reports.
Resolves: https://github.com/ksh93/ksh/issues/305
Resolves: https://github.com/ksh93/ksh/issues/316
44 lines
2.5 KiB
C
44 lines
2.5 KiB
C
/***********************************************************************
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* *
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* This software is part of the ast package *
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* Copyright (c) 1982-2012 AT&T Intellectual Property *
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* Copyright (c) 2020-2021 Contributors to ksh 93u+m *
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* and is licensed under the *
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* Eclipse Public License, Version 1.0 *
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* by AT&T Intellectual Property *
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* *
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* A copy of the License is available at *
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* http://www.eclipse.org/org/documents/epl-v10.html *
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* (with md5 checksum b35adb5213ca9657e911e9befb180842) *
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* *
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* Information and Software Systems Research *
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* AT&T Research *
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* Florham Park NJ *
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* *
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* David Korn <dgk@research.att.com> *
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* *
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***********************************************************************/
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#define SH_RELEASE_FORK "93u+m" /* only change if you develop a new ksh93 fork */
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#define SH_RELEASE_SVER "1.0.0-beta.2" /* semantic version number: https://semver.org */
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#define SH_RELEASE_DATE "2021-08-13" /* must be in this format for $((.sh.version)) */
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#define SH_RELEASE_CPYR "(c) 2020-2021 Contributors to ksh " SH_RELEASE_FORK
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/* Scripts sometimes field-split ${.sh.version}, so don't change amount of whitespace. */
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/* Arithmetic $((.sh.version)) uses the last 10 chars, so the date must be at the end. */
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#if _AST_ksh_release
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# define SH_RELEASE SH_RELEASE_FORK "/" SH_RELEASE_SVER " " SH_RELEASE_DATE
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#else
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# ifdef _AST_git_commit
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# define SH_RELEASE SH_RELEASE_FORK "/" SH_RELEASE_SVER "+" _AST_git_commit " " SH_RELEASE_DATE
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# else
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# define SH_RELEASE SH_RELEASE_FORK "/" SH_RELEASE_SVER "+dev " SH_RELEASE_DATE
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# endif
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#endif
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/*
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* For shcomp: the version number (0-255) for the binary bytecode header.
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* Only increase very rarely, i.e.: if incompatible changes are made that
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* cause bytecode from newer versions to fail on older versions of ksh.
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*/
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#define SHCOMP_HDR_VERSION 5
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