*.c *_init(): define in terms of corresponding *_INIT macro

Change the common patter in the codebase of duplicating the
initialization logic between an *_INIT macro and a
corresponding *_init() function to use the macro as the canonical
source of truth.

Now we no longer need to keep the function up-to-date with the macro
version. This implements a suggestion by Jeff King who found that
under -O2 [1] modern compilers will init new version in place without
the extra copy[1]. The performance of a single *_init() won't matter
in most cases, but even if it does we're going to be producing
efficient machine code to perform these operations.

1. https://lore.kernel.org/git/YNyrDxUO1PlGJvCn@coredump.intra.peff.net/

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/strbuf.c b/strbuf.c
index 4df30b4549..c8a5789694 100644
--- a/strbuf.c
+++ b/strbuf.c
@@ -52,8 +52,8 @@ char strbuf_slopbuf[1];
 
 void strbuf_init(struct strbuf *sb, size_t hint)
 {
-	sb->alloc = sb->len = 0;
-	sb->buf = strbuf_slopbuf;
+	struct strbuf blank = STRBUF_INIT;
+	memcpy(sb, &blank, sizeof(*sb));
 	if (hint)
 		strbuf_grow(sb, hint);
 }