Re: ZSH completion crash with "typeset compstate"

[Peter Stephenson <p.stephenson@xxxxxxxxxxx>]

On Sun, 04 Sep 2016 22:04:45 +0200
Mickaël THOMAS <mickael9@xxxxxxxxx> wrote:
> Found this by accident (I intended to use "typeset -p" for debugging).
> 
> % _f() { typeset compstate } ; compdef _f f
> % f
      ^<TAB>
> Program received signal SIGSEGV, Segmentation fault.

No great surprise this does something funny, the question is how to make
it a bit safer.

Here's one possible easy way: mark the parameter as being allowed to
have only a single instance, so you can't make a local copy with a
typeset.  The case above now produces an error message:

_f:typeset: compstate: can only have a single instance

I think trying to make compstate safe about multiple instances is both
difficult and pointless.

There's no undocumented overloading that prevents me from using 1<<20
for the new flag, is there?

pws

diff --git a/Src/Zle/complete.c b/Src/Zle/complete.c
index b28b95e..4bf238f 100644
--- a/Src/Zle/complete.c
+++ b/Src/Zle/complete.c
@@ -1238,8 +1238,9 @@ makecompparams(void)
 
     addcompparams(comprparams, comprpms);
 
-    if (!(cpm = createparam(COMPSTATENAME,
-			    PM_SPECIAL|PM_REMOVABLE|PM_LOCAL|PM_HASHED)))
+    if (!(cpm = createparam(
+	      COMPSTATENAME,
+	      PM_SPECIAL|PM_REMOVABLE|PM_SINGLE|PM_LOCAL|PM_HASHED)))
 	cpm = (Param) paramtab->getnode(paramtab, COMPSTATENAME);
     DPUTS(!cpm, "param not set in makecompparams");
 
diff --git a/Src/builtin.c b/Src/builtin.c
index da45300..3b82c9e 100644
--- a/Src/builtin.c
+++ b/Src/builtin.c
@@ -2266,6 +2266,10 @@ typeset_single(char *cname, char *pname, Param pm, UNUSED(int func),
 	    zerrnam(cname, "%s: restricted", pname);
 	    return pm;
 	}
+	if (pm->node.flags & PM_SINGLE) {
+	    zerrnam(cname, "%s: can only have a single instance", pname);
+	    return pm;
+	}
 	/*
 	 * For specials, we keep the same struct but zero everything.
 	 * Maybe it would be easier to create a new struct but copy
diff --git a/Src/zsh.h b/Src/zsh.h
index 36fddd0..87e6a98 100644
--- a/Src/zsh.h
+++ b/Src/zsh.h
@@ -1792,6 +1792,7 @@ struct tieddata {
 #define PM_ZSHSTORED	(1<<18) /* function stored in zsh form              */
 
 /* Remaining flags do not correspond directly to command line arguments */
+#define PM_SINGLE       (1<<20) /* special can only have a single instance  */
 #define PM_LOCAL	(1<<21) /* this parameter will be made local        */
 #define PM_SPECIAL	(1<<22) /* special builtin parameter                */
 #define PM_DONTIMPORT	(1<<23)	/* do not import this variable              */