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More fixes for subshell directory handling (re: 7bab9508, 5ee290c7)

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This commit fixes what are hopefully the two final aspects of #153:

1. If the present working directory does not exist (was moved or
   deleted) upon entering a virtual subshell, no PWD directory path
   is saved. Since restoring the state after exiting a virtual
   subshell is contingent on a previous PWD path existing, this
   resulted in entire aspects of the virtual subshell, such as the
   subshell function tree, not being cleaned up.
2. A separate problem is that 'cd ..' does not update PWD or OLDPWD
   when run from a nonexistent directory.

A reproducer exposing both problems is:

$ mkdir test
$ cd test
$ ksh -c '(subfn() { BAD; }; cd ..; echo subPWD==$PWD);
			typeset -f subfn; echo mainPWD==$PWD'
subPWD==/usr/local/src/ksh93/ksh/test
subfn() { BAD; };mainPWD==/usr/local/src/ksh93/ksh/test

Expected output:
subPWD==/usr/local/src/ksh93/ksh
mainPWD==/usr/local/src/ksh93/ksh/test

src/cmd/ksh93/bltins/cd_pwd.c:
- If path_pwd() fails to get the PWD (usually it no longer exists),
  don't set $OLDPWD to '.' as that is pointless; use $PWD instead.
  After cd'ing from a nonexistent directory, 'cd -' *should* fail
  and should not be equivalent to 'cd .'.
- Remove a redundant check for (!oldpwd) where it is always set.
- Do not prematurely return without setting PWD or OLDPWD if
  pathcanon() fails to canonicalise a nonexistent directory.
  Instead, fall back to setting PWD to the result of getcwd(3).

src/cmd/ksh93/sh/subshell.c:
- Minor stylistic adjustment. Some NULL macros sneaked in. This
  historic code base does not use them (yet); change to NIL(type*).
- sh_subshell(): Fix logic for determining whether to save/restore
  subshell state.
  1. When saving, 'if(!comsub || !shp->subshare)' is redundant;
     'if(!shp->subshare)' should be enough. If we're not in a
     subshare, state should be saved.
  2. When restoring, 'if(sp->shpwd)' is just nonsense as there is
     no guarantee that the PWD exists upon entering a subshell.
     Simply use the same 'if(!shp->subshare)'. Add an extra check
     for sp->pwd to avoid a possible segfault. Always restore the
     PWD on subshell exit and not only if shp->pwd is set.
- sh_subshell(): Issue fatal errors in libast's "panic" format.

src/cmd/ksh93/tests/builtins.sh:
- Adjust a relevant test to run err_exit() outside of the subshell
  so that any error is counted in the main shell.
- Add test for problem 2 described at the top.

src/cmd/ksh93/tests/subshell.sh:
- Add test for problems 1 and 2 based on reproducer above.

Resolves: https://github.com/ksh93/ksh/issues/153
This commit is contained in:
Martijn Dekker 2021-04-18 23:28:50 +01:00
parent b0a6c1bde5
commit feaf718f16
4 changed files with 67 additions and 38 deletions
Download patch file Download diff file Expand all files Collapse all files

39
src/cmd/ksh93/sh/subshell.c
View file

@ -219,7 +219,7 @@ void sh_subfork(void)
shp->subshell = 0;
shp->comsub = 0;
sp->subpid=0;
shp->st.trapcom[0] = (comsub==2 ? NULL : trap);
shp->st.trapcom[0] = (comsub==2 ? NIL(char*) : trap);
shp->savesig = 0;
/* sh_fork() increases ${.sh.subshell} but we forked an existing virtual subshell, so undo */
shgd->realsubshell--;
@ -581,7 +581,7 @@ Sfio_t *sh_subshell(Shell_t *shp,Shnode_t *t, volatile int flags, int comsub)
shp->comsub = comsub;
job.bktick_waitall = (comsub==1);
}
if(!comsub || !shp->subshare)
if(!shp->subshare)
{
struct subshell *xp;
sp->shpwd = shp->pwd;
@ -634,9 +634,9 @@ Sfio_t *sh_subshell(Shell_t *shp,Shnode_t *t, volatile int flags, int comsub)
else if(shp->st.trapcom[isig])
savsig[isig] = sh_strdup(shp->st.trapcom[isig]);
else
savsig[isig] = NULL;
savsig[isig] = NIL(char*);
}
/* this nonsense needed for $(trap) */
/* this is needed for var=$(trap) */
shp->st.otrapcom = (char**)savsig;
}
sp->cpid = shp->cpid;
@ -794,7 +794,7 @@ Sfio_t *sh_subshell(Shell_t *shp,Shnode_t *t, volatile int flags, int comsub)
job.curpgid = savejobpgid;
job.exitval = saveexitval;
shp->bckpid = sp->bckpid;
if(sp->shpwd) /* restore environment if saved */
if(!shp->subshare) /* restore environment if saved */
{
int n;
shp->options = sp->options;
@ -842,24 +842,21 @@ Sfio_t *sh_subshell(Shell_t *shp,Shnode_t *t, volatile int flags, int comsub)
free((void*)savsig);
}
shp->options = sp->options;
if(!shp->pwd || strcmp(sp->pwd,shp->pwd))
if(shp->pwd != sp->pwd && (!shp->pwd || !sp->pwd || strcmp(sp->pwd,shp->pwd)))
{
/* restore PWDNOD */
/* restore the present working directory */
Namval_t *pwdnod = sh_scoped(shp,PWDNOD);
if(shp->pwd)
{
#if _lib_fchdir
if(fchdir(sp->pwdfd) < 0)
if(fchdir(sp->pwdfd) < 0)
#else
if(chdir(sp->pwd) < 0)
if(!sp->pwd || chdir(sp->pwd) < 0)
#endif /* _lib_fchdir */
{
saveerrno = errno;
fatalerror = 2;
}
shp->pwd=sp->pwd;
path_newdir(shp,shp->pathlist);
{
saveerrno = errno;
fatalerror = 2;
}
shp->pwd=sp->pwd;
path_newdir(shp,shp->pathlist);
if(nv_isattr(pwdnod,NV_NOFREE))
pwdnod->nvalue.cp = (const char*)sp->pwd;
}
@ -939,17 +936,17 @@ Sfio_t *sh_subshell(Shell_t *shp,Shnode_t *t, volatile int flags, int comsub)
case 1:
shp->toomany = 1;
errno = saveerrno;
errormsg(SH_DICT,ERROR_system(1),e_redirect);
errormsg(SH_DICT,ERROR_SYSTEM|ERROR_PANIC,e_redirect);
UNREACHABLE();
case 2:
/* reinit PWD as it will be wrong */
shp->pwd = NULL;
shp->pwd = NIL(const char*);
path_pwd(shp,0);
errno = saveerrno;
errormsg(SH_DICT,ERROR_system(1),"Failed to restore PWD upon exiting subshell");
errormsg(SH_DICT,ERROR_SYSTEM|ERROR_PANIC,"Failed to restore PWD upon exiting subshell");
UNREACHABLE();
default:
errormsg(SH_DICT,ERROR_system(1),"Subshell error %d",fatalerror);
errormsg(SH_DICT,ERROR_SYSTEM|ERROR_PANIC,"Subshell error %d",fatalerror);
UNREACHABLE();
}
}