mkstring: minimum 7 char alloc size.

* lib.c (mkstring): Do not allocate less than 8 characters,
including null terminator, to the string. This speeds up code
which builds up strings from empty, one character at a time.

1 files changed, 3 insertions, 2 deletions

diff --git a/lib.c b/lib.c
index ff9ec00b..4f5cb11d 100644
--- a/lib.c
+++ b/lib.c
@@ -5285,13 +5285,14 @@ val mkstring(val len, val ch_in)
                  (uw_throwf(range_error_s, lit("~a: negative size ~s specified"),
                             self, len, nao), 0),
                  c_num(len, self));
-  wchar_t *str = chk_wmalloc(l + 1);
+  size_t a = max(7, l);
+  wchar_t *str = chk_wmalloc(a + 1);
   val s = string_own(str);
   val ch = default_arg_strict(ch_in, chr(' '));
   wmemset(str, c_chr(ch), l);
   str[l] = 0;
   s->st.len = len;
-  s->st.alloc = c_num(len, self) + 1;
+  s->st.alloc = a;
   return s;
 }