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Fork before entering shared-state command substitution

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The code contains various checks to see if a subshell needs to
fork, like this one in the ulimit builtin:

	if(shp->subshell && !shp->subshare)
		sh_subfork();

All checks of this form are fatally broken, as each one of them
causes shared-state command substitutions to ignore parent virtual
subshells.

Currently the only feasible way to fix this is to fork a virtual
subshell before executing a shared-state command substitution in
it. In the long term I think shared-state command substitutions
should probably be redesigned to disassociate them completely from
the virtual subshell mechanism.

src/cmd/ksh93/sh/macro.c: comsubst():
- If we're in a non-subshare virtual subshell, fork it before
  entering a type 2 (subshare) command substitution.

src/cmd/ksh93/sh/subshell.c:
- sh_assignok(): Remove subshare fix from 911d6b06 as it's
  redundant now that the parent of a subshare is never a virtual
  subshell. Go back to not doing anything if the current "subshell"
  is a subshare.
- sh_subtracktree(), sh_subfuntree(): Similarly, remove the
  now-redundant subshare fixes from 13c57e4b.

src/cmd/ksh93/sh/xec.c: sh_exec():
- Fix a separate bug: only fork a virtual subshell before running a
  background job if that "subshell" is not a subshare.

src/cmd/ksh93/tests/subshell.sh:
- Add test for bug fixed in xec.c.
- Add tests for 'ulimit', 'builtin' and 'exec' run in subshare
  within subshell -- all commands that use checks of the form
  'if(sh.subshell && !sh.subshare) sh_subfork();'.

Resolves: https://github.com/ksh93/ksh/issues/289
This commit is contained in:
Martijn Dekker 2021-05-01 00:47:39 +01:00
parent 72fe631b2f
commit 88a1f3d661
5 changed files with 29 additions and 38 deletions
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@ -13,6 +13,9 @@ Any uppercase BUG_* names are modernish shell bug IDs.
- Fixed a bug introduced on 2020-09-05 that caused "echo ${var:+'{}'}"
to be misparsed.
- Fixed: the effects of 'builtin', 'exec' and 'ulimit' leaked out of a parent
virtual subshell if run from a ${ shared-state; } command substitution.
2021-04-26:
- Fixed a bug introduced on 2021-02-20 in which a shared-state command