Read-only special variables and "local +h"

Read-only special variables and "local +h"

[Bart Schaefer]

Try running the following function.

blam() {
    setopt localoptions extendedglob
    zmodload -i zsh/parameter
    set $(typeset +r)
    while (( $# )); do
        [[ $1 = [[:alnum:]]# ]] && {
	    print -n "assigning to local $1\: "
            eval \( local +h $1 \; ${(qf)$(set | grep \^$1=)} \)
	    case $? in
	    0) print no error detected;;
	    136) print floating point exception;;
	    139) print segmentation fault;;
	    *) print other failure;;
            esac
        }
        shift
    done
}

I get:

assigning to local ARGC: segmentation fault
assigning to local ERRNO: segmentation fault
assigning to local LINENO: segmentation fault
assigning to local PPID: segmentation fault
assigning to local TTYIDLE: segmentation fault
assigning to local builtins: floating point exception
assigning to local funcstack: no error detected
assigning to local history: floating point exception
assigning to local historywords: no error detected
assigning to local jobdirs: no error detected
assigning to local jobstates: no error detected
assigning to local jobtexts: no error detected
assigning to local modules: floating point exception
assigning to local parameters: floating point exception
assigning to local reswords: no error detected
assigning to local status: no error detected
assigning to local userdirs: floating point exception

-- 
Bart Schaefer                                 Brass Lantern Enterprises
http://www.well.com/user/barts              http://www.brasslantern.com

Re: Read-only special variables and "local +h"

[Peter Stephenson]

Bart reminded me about this.  (Just in case you thought I was looking at it
voluntarily...)

"Bart Schaefer" wrote:
> Try running the following function.
> 
> blam() {
>     setopt localoptions extendedglob
>     zmodload -i zsh/parameter
>     set $(typeset +r)
>     while (( $# )); do
>         [[ $1 = [[:alnum:]]# ]] && {
> 	    print -n "assigning to local $1\: "
>             eval \( local +h $1 \; ${(qf)$(set | grep \^$1=)} \)
> 	    case $? in
> 	    0) print no error detected;;
> 	    136) print floating point exception;;
> 	    139) print segmentation fault;;
> 	    *) print other failure;;
>             esac
>         }
>         shift
>     done
> }

I've fixed these, but the really good news is that mostly this wasn't my
fault.

The segmentation violations from the integer functions were occurring
because there was only one nullsetfn for dealing with assignments which
shouldn't happen, which assumed the parameter was scalar and tries to free
it.  It wasn't and it couldn't.

The floating point exceptions from the special hashes in the parameter
module were Linux's sui generis interpretation of having an integer
expression modulo zero, because the special hash had a size of 0 which was
being copied faithfully to the hash where the values were being saved
during the function call.  In most cases it would be pretty pointless to
save this particular hash at all --- but that's why it usually has the -h
bit set, because it assumes if you're making it local you want to do
something entirely different with it; it's entirely logical to save it when
you explicitly make it localisable as a special.  So I've just fixed the
size problem.

I think I'm daring enough to assume the problems are, er, local enough to
be able to commit this patch without the world blowing up in our faces.

By the way, we definitely need a way (similar to the -h flag) of telling
set, typeset and friends that they are not to display the values of certain
parameters, even if the `+' flag wasn't given.  Currently using `set' and
`typeset' on their own is virtually useless with the parameters module
loaded.  Even non-interactively there are problems --- GNU grep is
sensitive to eight-bit characters and refuses to grep the `set' output
unless you give it the -a flag, so Bart's blam function was actually
printing out lots of `binary output matches' messages.

I can't resist giving the output I get after the patch.

assigning to local ARGC: no error detected
assigning to local ERRNO: no error detected
assigning to local LINENO: no error detected
assigning to local PPID: no error detected
assigning to local TTYIDLE: no error detected
assigning to local builtins: no error detected
assigning to local funcstack: no error detected
assigning to local history: no error detected
assigning to local historywords: no error detected
assigning to local jobdirs: no error detected
assigning to local jobstates: no error detected
assigning to local jobtexts: no error detected
assigning to local modules: no error detected
assigning to local parameters: no error detected
assigning to local reswords: no error detected
assigning to local status: no error detected
assigning to local userdirs: no error detected

Index: Src/params.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/params.c,v
retrieving revision 1.12
diff -u -r1.12 params.c
--- Src/params.c	2000/05/31 08:56:24	1.12
+++ Src/params.c	2000/05/31 21:39:13
@@ -134,8 +134,8 @@
 #define SFN(X) BR(((void (*)_((Param, char *)))(X)))
 #define GFN(X) BR(((char *(*)_((Param)))(X)))
 #define IPDEF1(A,B,C,D) {NULL,A,PM_INTEGER|PM_SPECIAL|D,BR(NULL),SFN(C),GFN(B),stdunsetfn,10,NULL,NULL,NULL,0}
-IPDEF1("#", poundgetfn, nullsetfn, PM_READONLY),
-IPDEF1("ERRNO", errnogetfn, nullsetfn, PM_READONLY),
+IPDEF1("#", poundgetfn, nullintsetfn, PM_READONLY),
+IPDEF1("ERRNO", errnogetfn, nullintsetfn, PM_READONLY),
 IPDEF1("GID", gidgetfn, gidsetfn, PM_DONTIMPORT | PM_RESTRICTED),
 IPDEF1("EGID", egidgetfn, egidsetfn, PM_DONTIMPORT | PM_RESTRICTED),
 IPDEF1("HISTSIZE", histsizegetfn, histsizesetfn, PM_RESTRICTED),
@@ -143,17 +143,17 @@
 IPDEF1("SECONDS", secondsgetfn, secondssetfn, 0),
 IPDEF1("UID", uidgetfn, uidsetfn, PM_DONTIMPORT | PM_RESTRICTED),
 IPDEF1("EUID", euidgetfn, euidsetfn, PM_DONTIMPORT | PM_RESTRICTED),
-IPDEF1("TTYIDLE", ttyidlegetfn, nullsetfn, PM_READONLY),
+IPDEF1("TTYIDLE", ttyidlegetfn, nullintsetfn, PM_READONLY),
 
 #define IPDEF2(A,B,C,D) {NULL,A,PM_SCALAR|PM_SPECIAL|D,BR(NULL),SFN(C),GFN(B),stdunsetfn,0,NULL,NULL,NULL,0}
 IPDEF2("USERNAME", usernamegetfn, usernamesetfn, PM_DONTIMPORT|PM_RESTRICTED),
-IPDEF2("-", dashgetfn, nullsetfn, PM_READONLY),
+IPDEF2("-", dashgetfn, nullstrsetfn, PM_READONLY),
 IPDEF2("histchars", histcharsgetfn, histcharssetfn, PM_DONTIMPORT),
 IPDEF2("HOME", homegetfn, homesetfn, 0),
 IPDEF2("TERM", termgetfn, termsetfn, 0),
 IPDEF2("WORDCHARS", wordcharsgetfn, wordcharssetfn, 0),
 IPDEF2("IFS", ifsgetfn, ifssetfn, PM_DONTIMPORT),
-IPDEF2("_", underscoregetfn, nullsetfn, PM_READONLY),
+IPDEF2("_", underscoregetfn, nullstrsetfn, PM_READONLY),
 
 #ifdef USE_LOCALE
 # define LCIPDEF(name) IPDEF2(name, strgetfn, lcsetfn, PM_UNSET)
@@ -176,7 +176,7 @@
 # endif
 #endif /* USE_LOCALE */
 
-#define IPDEF4(A,B) {NULL,A,PM_INTEGER|PM_READONLY|PM_SPECIAL,BR((void *)B),SFN(nullsetfn),GFN(intvargetfn),stdunsetfn,10,NULL,NULL,NULL,0}
+#define IPDEF4(A,B) {NULL,A,PM_INTEGER|PM_READONLY|PM_SPECIAL,BR((void *)B),SFN(nullintsetfn),GFN(intvargetfn),stdunsetfn,10,NULL,NULL,NULL,0}
 IPDEF4("!", &lastpid),
 IPDEF4("$", &mypid),
 IPDEF4("?", &lastval),
@@ -224,7 +224,7 @@
 
 /* The following parameters are not avaible in sh/ksh compatibility *
  * mode. All of these has sh compatible equivalents.                */
-IPDEF1("ARGC", poundgetfn, nullsetfn, PM_READONLY),
+IPDEF1("ARGC", poundgetfn, nullintsetfn, PM_READONLY),
 IPDEF2("HISTCHARS", histcharsgetfn, histcharssetfn, PM_DONTIMPORT),
 IPDEF4("status", &lastval),
 IPDEF7("prompt", &prompt),
@@ -266,7 +266,10 @@
 mod_export HashTable
 newparamtable(int size, char const *name)
 {
-    HashTable ht = newhashtable(size, name, NULL);
+    HashTable ht;
+    if (!size)
+	size = 17;
+    ht = newhashtable(size, name, NULL);
 
     ht->hash        = hasher;
     ht->emptytable  = emptyhashtable;
@@ -2189,15 +2192,24 @@
     free(val);		/* not freearray() */
 }
 
-/* This function is used as the set function for      *
- * special parameters that cannot be set by the user. */
+/*
+ * These functions are used as the set function for special parameters that
+ * cannot be set by the user.  The set is incomplete as the only such
+ * parameters are scalar and integer.
+ */
 
 /**/
 void
-nullsetfn(Param pm, char *x)
+nullstrsetfn(Param pm, char *x)
 {
     zsfree(x);
 }
+
+/**/
+void
+nullintsetfn(Param pm, zlong x)
+{}
+
 
 /* Function to get value of generic special integer *
  * parameter.  data is pointer to global variable   *

-- 
Peter Stephenson <pws@pwstephenson.fsnet.co.uk>
Work: pws@CambridgeSiliconRadio.com
Web: http://www.pwstephenson.fsnet.co.uk