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Fix unsetting aliases in subshells

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Aliases can now be correctly unset within subshell environments
(such as ( ... ), $(command substitutions), etc), as well as
non-subshell "shared" command substitutions (${ ...; }). Before,
attempts to unset aliases within these were silently ignored.

Prior discussion: https://github.com/att/ast/issues/108

Subshell alias trees are only referenced in a few places in the
code, *and* have always been broken, so this commit gets rid of the
whole notion of a subshell alias tree. Instead, there is now just
one flat alias tree, and subshells fork into a separate process
when aliases are set or unset within them. It is not really
conceivable that this could be a performance-sensitive operation,
or even a common one, so this is a clean fix with no downside.

src/cmd/ksh93/include/defs.h:
- Remove sh_subaliastree() definition.

src/cmd/ksh93/sh/subshell.c:
- Remove salias element (pointer to subshell alias tree) from
  subshell struct.
- Remove sh_subaliastree() function.
- sh_subshell(): Remove alias subshell tree cleanup.

src/cmd/ksh93/bltins/typeset.c:
- b_alias(): If in subshell, fork before setting alias.
- b_unalias(): If in subshell, fork before unsetting alias.
- unall(): Remove sh_subaliastree() call.

src/cmd/ksh93/sh/name.c:
- nv_open(): Remove sh_subaliastree() call.

src/cmd/ksh93/tests/subshell.sh:
- Add regression tests for unsetting or redefining aliases within
  subshells.

(cherry picked from commit 12a15605b9521a2564a6e657905705a060e89095)
This commit is contained in:
Martijn Dekker 2020-05-29 08:27:53 +01:00
parent 047cb3303c
commit ec888867fd
6 changed files with 36 additions and 32 deletions
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2
src/cmd/ksh93/sh/name.c
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@ -1390,8 +1390,6 @@ Namval_t *nv_open(const char *name, Dt_t *root, int flags)
msg = e_aliname;
while((c= *(unsigned char*)cp++) && (c!='=') && (c!='/') &&
(c>=0x200 || !(c=sh_lexstates[ST_NORM][c]) || c==S_EPAT || c==S_COLON));
if(shp->subshell && c=='=')
root = sh_subaliastree(1);
if(c= *--cp)
*cp = 0;
np = nv_search(name, root, (flags&NV_NOADD)?0:NV_ADD);