Re: Possible huge setarrvalue optimization

[Sebastian Gniazdowski <psprint@fastmail.com>]

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OK, the patch should now be complete. There is condition whether to use
all-duplicate code path:

        if (pre_assignment_length != post_assignment_length ||
        v->pm->node.flags & (PM_SPECIAL|PM_UNIQUE)) {

This covers special arrays and uniq arrays, that should be always
calling setfn() to trigger side-effects. Other arrays use this code:

            /* v->start is 0-based */
            p = old + v->start;
            for (r = val; *r;) {
                /* Free previous string */
                zsfree(*p);
                /* Give away ownership of the string */
                *p++ = *r++;
            }

And it should be OK, zsfree() for non-special array should be always
successful.

-- 
  Sebastian Gniazdowski
  psprint@fastmail.com

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diff --git a/Src/params.c b/Src/params.c
index ef72cba..eac8375 100644
--- a/Src/params.c
+++ b/Src/params.c
@@ -2654,24 +2654,36 @@ setarrvalue(Value v, char **val)
 	    v->end = v->start;
 
 	post_assignment_length = v->start + arrlen(val);
-	if (v->end <= pre_assignment_length)
-	    post_assignment_length += pre_assignment_length - v->end + 1;
-
-	p = new = (char **) zshcalloc(sizeof(char *)
-		                      * (post_assignment_length + 1));
-
-	for (i = 0; i < v->start; i++)
-	    *p++ = i < pre_assignment_length ? ztrdup(*q++) : ztrdup("");
-	for (r = val; *r;) {
-            /* Give away ownership of the string */
-	    *p++ = *r++;
-	}
-	if (v->end < pre_assignment_length)
-	    for (q = old + v->end; *q;)
-		*p++ = ztrdup(*q++);
-	*p = NULL;
 
-	v->pm->gsu.a->setfn(v->pm, new);
+	if (v->end <= pre_assignment_length)
+	    post_assignment_length += pre_assignment_length - v->end;
+
+        if (pre_assignment_length != post_assignment_length || v->pm->node.flags & (PM_SPECIAL|PM_UNIQUE)) {
+            p = new = (char **) zshcalloc(sizeof(char *)
+                                          * (post_assignment_length + 1));
+
+            for (i = 0; i < v->start; i++)
+                *p++ = i < pre_assignment_length ? ztrdup(*q++) : ztrdup("");
+            for (r = val; *r;) {
+                /* Give away ownership of the string */
+                *p++ = *r++;
+            }
+            if (v->end < pre_assignment_length)
+                for (q = old + v->end; *q;)
+                    *p++ = ztrdup(*q++);
+            *p = NULL;
+
+            v->pm->gsu.a->setfn(v->pm, new);
+        } else {
+            /* v->start is 0-based */
+            p = old + v->start;
+            for (r = val; *r;) {
+                /* Free previous string */
+                zsfree(*p);
+                /* Give away ownership of the string */
+                *p++ = *r++;
+            }
+        }
 
         /* Ownership of all strings has been
          * given away, can plainly free */