From 707ab6c2626575cd090a2ba02db17306a25d49ed Mon Sep 17 00:00:00 2001
From: Kaz Kylheku <kaz@kylheku.com>
Date: Wed, 29 Jan 2025 20:37:39 -0800
Subject: vector: ensure minimum alloc size.

Like in a recent commit for mkstring, we impose a minimum
allocation size of 6 for vectors, which means 8 cells
together with the two informaton words at the base of
the vector.

* lib.c (vec_own): Take an alloc parameter in addition
to the length, which is stored in v[vec_alloc].
(vector): Impose a minimum alloc size of 6.
(copy_vec, nested_vec_of_v): Pass alloc parameter
to vec_own which is the same as the length parameter;
i.e. no behavior change for these functions.
---
 lib.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/lib.c b/lib.c
index 99674be5..44f2b1ef 100644
--- a/lib.c
+++ b/lib.c
@@ -9665,7 +9665,7 @@ static val *vec_allocate(ucnum len, val self)
   return coerce(val *, chk_xalloc(size, sizeof (val), self));
 }
 
-static val vec_own(val *v, val length)
+static val vec_own(val *v, val length, val alloc)
 {
   val vec = make_obj();
 
@@ -9675,7 +9675,7 @@ static val vec_own(val *v, val length)
 #endif
   v += 2;
   vec->v.vec = v;
-  v[vec_alloc] = length;
+  v[vec_alloc] = alloc;
   v[vec_length] = length;
 
   return vec;
@@ -9695,8 +9695,9 @@ val vector(val length, val initval)
   val self = lit("vector");
 
   ucnum len = c_unum(length, self);
-  val *v = vec_allocate(len, self);
-  val vec = vec_own(v, length);
+  ucnum alloc = max(6, len);
+  val *v = vec_allocate(alloc, self);
+  val vec = vec_own(v, length, unum(alloc));
   vec_init(v, len, initval);
   return vec;
 }
@@ -9867,7 +9868,7 @@ val copy_vec(val vec_in)
   val length = length_vec(vec_in);
   ucnum len = c_unum(length, self);
   val *v = vec_allocate(len, self);
-  val vec = vec_own(v, length);
+  val vec = vec_own(v, length, length);
   memcpy(v + 2, vec_in->v.vec, len * sizeof *v);
   return vec;
 }
@@ -10166,7 +10167,7 @@ val nested_vec_of_v(val initval, struct args *args)
       for (i = 0; i < n; i++)
         rawvec[i + 2] = nested_vec_of_v(initval, args_copy);
 
-      vec = vec_own(rawvec, dim);
+      vec = vec_own(rawvec, dim, dim);
       gc_state(gc_save);
       return vec;
     } else {
-- 
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