nv_disc(NV_LAST) loses trailing shell context from discipline stack (#276)

citrus-it · web-flow · commit 2fdf394b996c · 2021-04-15T14:41:32.000+01:00
This is the underlying cause for the issue worked around in 3654ee7. The following explanation refers to the current illumos version of ksh93 and shows output from illumos' modular debugger: https://illumos.org/books/dev/debugging.html Each environment variable (name/value pair) has a linked list of disciplines attached to it, and at the end of that list there is optionally a shell context pointer. For example, for the EDITOR variable: > ::bp libshell.so.1`put_ed > ::run $ $ EDITOR=vim > ::stack ! head -1 libshell.so.1`put_ed+0x14(e06208, e01c58, 0, dced90) > e06208::print Namval_t { nvname = 0xfffffbffeec40a0e "EDITOR" nvfun = 0xdced90 nvalue = 0 } > e06208::print Namval_t nvfun | ::print Namfun_t { disc = libshell.so.1`EDITOR_disc next = libshell.so.1`sh+0x710 } Here, the EDITOR Namval_t has a discipline stack containing EDITOR_disc and &Shell_t.nvfun. The problem arises when a new discipline is pushed onto the stack, such as when using typeset -u to add an upper-case translation discipline. $ typeset -u EDITOR > e06208::print Namval_t { nvname = 0xfffffbffeec40a0e "EDITOR" nvfun = 0xdced90 nvalue = 0xe0fdb0 "vim" } > e06208::print Namval_t nvfun | ::print Namfun_t { disc = libshell.so.1`EDITOR_disc next = 0xdc27a0 } > e06208::print Namval_t nvfun | ::print Namfun_t next | ::print Namfun_t { disc = libshell.so.1`TRANS_disc next = 0 } TRANS_disc has been pushed onto the end of the discipline stack, but the shell handle has been lost. With this change, the attributes and variables tests pass (this is on illumos where this change originates).
diff --git a/src/cmd/ksh93/sh/nvdisc.c b/src/cmd/ksh93/sh/nvdisc.c
@@ -752,7 +752,7 @@ Namfun_t *nv_disc(register Namval_t *np, register Namfun_t* fp, int mode)
 			if(lp && !lp->disc)
 				fp->next = lp;
 			else
-				fp->next = 0;
+				fp->next = *lpp;
 		}
 		else
 		{

Original file line number	Diff line number	Diff line change
`@@ -752,7 +752,7 @@ Namfun_t nv_disc(register Namval_t np, register Namfun_t* fp, int mode)`
`752`	`752`	`if(lp && !lp->disc)`
`753`	`753`	`fp->next = lp;`
`754`	`754`	`else`
`755`		`- fp->next = 0;`
	`755`	`+ fp->next = *lpp;`
`756`	`756`	`}`
`757`	`757`	`else`
`758`	`758`	`{`