Let the OS clear new large strings of NUL

On my platform, this sped up (make-string 4000000000 0) from 2.5
to 0.015 seconds (not that people should want to do this much :-).
* src/alloc.c (allocate_string_data): New arg CLEARIT.
Callers changed.
(Fmake_string): Prefer calloc to malloc+memset when allocating a
large string of NUL bytes.
(make_clear_string): New function.
(make_uninit_string): Use it.
(make_clear_multibyte_string): New function.
(make_uninit_multibyte_string): Use it.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/data.c b/src/data.c
index 56e363f16b6..c8445e7d874 100644
--- a/src/data.c
+++ b/src/data.c
@@ -2321,7 +2321,7 @@ bool-vector.  IDX starts at 0.  */)
 
               memcpy (str, SDATA (array), nbytes);
               allocate_string_data (XSTRING (array), nchars,
-                                    nbytes + new_bytes - prev_bytes);
+                                    nbytes + new_bytes - prev_bytes, false);
               memcpy (SDATA (array), str, idxval_byte);
               p1 = SDATA (array) + idxval_byte;
               memcpy (p1 + new_bytes, str + idxval_byte + prev_bytes,