34068: create tempfiles without forking, and safe temp directory creation

Completion/Base/Widget/_complete_debug

@@ -9,7 +9,7 @@ local pager w="${(qq)words}"
 integer debug_fd=-1
 {
   if [[ -t 2 ]]; then
-    mv -f =(:) $tmp &&
+    mv -f =(<<<'') $tmp &&
     exec {debug_fd}>&2 2>| $tmp
   fi
 

Completion/Unix/Command/_cvs

@@ -704,15 +704,18 @@ _cvs_sub_modules() {
 _cvs_run() {
   local cvsroot="$1" dir="$2"
   shift 2
-  local d=/tmp/zsh-cvs-work-$$
-  mkdir $d >&/dev/null
-  cd $d
-  mkdir CVS >&/dev/null
+  local d=${TMPPREFIX:-/tmp/zsh}-cvs-work-$$
+  rm -rf $d
+  mkdir $d &&
+  (
+  chmod 0700 $d &&
+  builtin cd -q $d &&
+  mkdir CVS >&/dev/null || return 1
   print -r - "$cvsroot" > CVS/Root
   print "$dir" > CVS/Repository
   print D > CVS/Entries
   CVS_IGNORE_REMOTE_ROOT= cvs "$@"
-  cd $OLDPWD
+  )
   rm -rf $d
 }
 

Completion/compinstall

@@ -1958,8 +1958,8 @@ if [[ -z $ifile || -d $ifile ]] ||
 fi
 
 local tmpout=${TMPPREFIX:-/tmp/zsh}compinstall$$
-mv -f =(:) $tmpout &&	# safe tempfile creation
-mv -f =(:) ${tmpout}x || return 1
+mv -f =(<<<'') $tmpout &&	# safe tempfile creation
+mv -f =(<<<'') ${tmpout}x || return 1
 
 #
 # Assemble the complete set of lines to