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Add ${.sh.pid} as an alternative to $BASHPID (#109)

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This variable is like Bash's $BASHPID, but in virtual subshells
it will retain its previous value as virtual subshells don't fork.
Both $BASHPID and ${.sh.pid} are different from $$ as the latter
is only set to the parent shell's process ID (i.e. it isn't set
to the process ID of the current subshell).

src/cmd/ksh93/include/defs.h:
- Add 'current_pid' for storing the current process ID at a valid
  memory address.
- Change 'ppid' from 'int32_t' to 'pid_t', as the return value from
  'getppid' is of the 'pid_t' data type.

src/cmd/ksh93/data/variables.c,
src/cmd/ksh93/include/variables.h,
src/cmd/ksh93/sh/init.c,
src/cmd/ksh93/sh/xec.c:
 - Add the ${.sh.pid} variable as an alternative to $BASHPID.
   The process ID is stored in a struct before ${.sh.pid} is set
   as environment variables are pointers that must point to a
   valid memory address. ${.sh.pid} is updated by the _sh_fork()
   function, which is called when ksh forks a new process with
   sh_fork() or sh_ntfork().

src/cmd/ksh93/tests/variables.sh:
- Add ${.sh.pid} to the list of special variables and add three
  regression tests for ${.sh.pid}.

src/cmd/ksh93/tests/subshell.sh:
- Update the PATH forking regression test to use ${.sh.pid} and
  remove the TODO note.
This commit is contained in:
Johnothan King 2020-08-06 18:53:25 -07:00 • committed by GitHub
parent f9fdbfc9e9
commit 9de65210c6
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9 changed files with 45 additions and 7 deletions
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7
src/cmd/ksh93/tests/subshell.sh
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@ -747,14 +747,13 @@ v=$($SHELL $testvars) && [[ "$v" == "a= b= c=0" ]] || err_exit 'variables set in
# ======
# Setting PATH in virtual subshell should trigger a fork; restoring PATH after leaving virtual subshell should not.
# TODO: it would be really nice to have a ${.sh.pid} for this sort of test (like $BASHPID on bash)...
SHELL=$SHELL "$SHELL" -c '
(
"$SHELL" -c "echo DEBUG \$PPID"
echo "DEBUG ${.sh.pid}"
readonly PATH
"$SHELL" -c "echo DEBUG \$PPID"
echo "DEBUG ${.sh.pid}"
)
"$SHELL" -c "echo DEBUG \$PPID"
echo "DEBUG ${.sh.pid}"
: extra command to disable "-c" exec optimization
' | awk '/^DEBUG/ { pid[NR] = $2; } END { exit !(pid[1] == pid[2] && pid[2] == pid[3]); }' \
|| err_exit "setting PATH to readonly in subshell triggers an erroneous fork"