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Properly fix $LINENO crash on ARM (re: 23b7a163) and other bugs

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The typecast fix was insufficient, avoiding the crash only when
compiling with optimisation disabled. The real problem is that
put_lineno() was passed a misaligned pointer, and that the value
didn't actually contain a double but a string. The bug occurred
when restoring the LINENO value upon exiting a virtual subshell.

Thanks to Harald van Dijk for figuring out the fix.

src/cmd/ksh93/sh/subshell.c: nv_restore():
- When restoring a special variable as defined by nv_cover(),
  do not pass either the np->nvflag bits or NV_NOFREE. Why?
  * The np->nvflag bits are not needed. They are also harmful
    because they may include the NV_INTEGER bit. This is set
    when the value is numeric. However, nv_getval() always
    returns the value in string form, converting it if it is
    numeric. So the NV_INTEGER flag should never be passed
    to nv_putval() when it uses the result of nv_getval().
  * According to nval.3, the NV_NOFREE flag stops nv_putval() from
    creating a copy of the value. But this should be unnecessary
    because the earlier _nv_unset(mp,NV_RDONLY|NV_CLONE) should
    ensure there is no previous value. In addition, the NV_NOFREE
    flag triggered another bug that caused the value of SECONDS to
    be corrupted upon restoring it when exiting a virtual subshell.
- When restoring a regular variable, copy the entire nvalue union
  and not just the 'cp' member. In practice this worked because
  no current member of the nvalue union is larger than a pointer.
  However, there is no guarantee it will stay that way.

src/cmd/ksh93/tests/leaks.sh:
- Add disabled test for a memory leak that was discovered in the
  course of dealing with this bug. The fix doesn't introduce or
  influence it. It will have to be dealt with later.

src/cmd/ksh93/tests/locale.sh:
- Add test for restoring locale on leaving virtual subshell.
  https://github.com/ksh93/ksh/issues/253#issuecomment-815290154

src/cmd/ksh93/tests/variables.sh:
- Test against corruption of SECONDS on leaving virtual subshell.
  https://github.com/ksh93/ksh/issues/253#issuecomment-815191052

Co-authored-by: Harald van Dijk <harald@gigawatt.nl>
Progresses: https://github.com/ksh93/ksh/issues/253
This commit is contained in:
Martijn Dekker 2021-04-08 00:10:07 +01:00
parent 23b7a163f7
commit 997ad43bbf
4 changed files with 38 additions and 3 deletions
Download patch file Download diff file Expand all files Collapse all files

10
src/cmd/ksh93/tests/variables.sh
View file

@ -1261,5 +1261,15 @@ got="$($SHELL -c 'PS4="${.sh.subshell}"; echo ${.sh.subshell}')"
[[ "$exp" == "$got" ]] || err_exit "\${.sh.subshell} is wrongly unset in the \$PS4 prompt" \
"(expected $(printf %q "$exp"), got $(printf %q "$got"))"
# ======
# Corruption of SECONDS on leaving virtual subshell
# https://github.com/ksh93/ksh/issues/253#issuecomment-815191052
osec=$SECONDS
(SECONDS=20)
nsec=$SECONDS
if ((nsec<osec || nsec>osec+0.1))
then err_exit "SECONDS corrupted after leaving virtual subshell (expected $osec, got $nsec)"
fi
# ======
exit $((Errors<125?Errors:125))