Fix up ugly open-coded "alloc_nr()" user in object.c

Fix up ugly open-coded "alloc_nr()" user in object.c

[Linus Torvalds]

When adding objects to the object/mode array, we used to have our own 
alloc_nr() implementation, rather than use the normal one.

And since the normal one is arguably a bit nicer (still grows the 
allocation exponentially, just not by more-than-doubling it every time), 
why not just use it?

That array of objects ends up being really quite big when you force a 
while repack of a big project, and while we might end up doing a few more 
xreallocs in the process, we also hopefully don't end up with a final 
allocation that is quite as wastefully big.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

  That was an overkill of a situation for a trivial patch that I don't 
  think is in the least interesting or even important. I really don't care 
  if you take this, Junio, but it seemed the obvious one-liner to do, so 
  I'm sending it in anyway.

 object.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/object.c b/object.c
index 16793d9..fdd6ceb 100644
--- a/object.c
+++ b/object.c
@@ -245,7 +245,7 @@ void add_object_array_with_mode(struct object *obj, const char *name, struct obj
 	struct object_array_entry *objects = array->objects;
 
 	if (nr >= alloc) {
-		alloc = (alloc + 32) * 2;
+		alloc = alloc_nr(alloc);
 		objects = xrealloc(objects, alloc * sizeof(*objects));
 		array->alloc = alloc;
 		array->objects = objects;

Re: Fix up ugly open-coded "alloc_nr()" user in object.c

[Jeff King]

On Sat, Jun 16, 2007 at 10:30:22AM -0700, Linus Torvalds wrote:

> When adding objects to the object/mode array, we used to have our own 
> alloc_nr() implementation, rather than use the normal one.
> 
> And since the normal one is arguably a bit nicer (still grows the 
> allocation exponentially, just not by more-than-doubling it every time), 
> why not just use it?

How about using the new ALLOC_GROW macro to make it even shorter? I also
got rid of the aliased variables, which IMO just make it harder to see
what's going on.

---
 object.c |   19 +++++--------------
 1 files changed, 5 insertions(+), 14 deletions(-)

diff --git a/object.c b/object.c
index 16793d9..064e423 100644
--- a/object.c
+++ b/object.c
@@ -240,18 +240,9 @@ void add_object_array(struct object *obj, const char *name, struct object_array
 
 void add_object_array_with_mode(struct object *obj, const char *name, struct object_array *array, unsigned mode)
 {
-	unsigned nr = array->nr;
-	unsigned alloc = array->alloc;
-	struct object_array_entry *objects = array->objects;
-
-	if (nr >= alloc) {
-		alloc = (alloc + 32) * 2;
-		objects = xrealloc(objects, alloc * sizeof(*objects));
-		array->alloc = alloc;
-		array->objects = objects;
-	}
-	objects[nr].item = obj;
-	objects[nr].name = name;
-	objects[nr].mode = mode;
-	array->nr = ++nr;
+	ALLOC_GROW(array->objects, array->nr, array->alloc);
+	array->objects[array->nr].item = obj;
+	array->objects[array->nr].name = name;
+	array->objects[array->nr].mode = mode;
+	array->nr++;
 }

Re: Fix up ugly open-coded "alloc_nr()" user in object.c

[Olivier Galibert]

On Sat, Jun 16, 2007 at 02:21:34PM -0400, Jeff King wrote:
> How about using the new ALLOC_GROW macro to make it even shorter? I also
> got rid of the aliased variables, which IMO just make it harder to see

> what's going on.
> +	ALLOC_GROW(array->objects, array->nr, array->alloc);
> +	array->objects[array->nr].item = obj;
> +	array->objects[array->nr].name = name;
> +	array->objects[array->nr].mode = mode;
> +	array->nr++;

Unless the ALLOC_GROW semantics are weird, shouldn't that be:
  ALLOC_GROW(array->objects, array->nr+1, array->alloc);

  OG.

Re: Fix up ugly open-coded "alloc_nr()" user in object.c

[Jeff King]

On Sun, Jun 17, 2007 at 12:15:06AM +0200, Olivier Galibert wrote:

> > +	ALLOC_GROW(array->objects, array->nr, array->alloc);
> 
> Unless the ALLOC_GROW semantics are weird, shouldn't that be:
>   ALLOC_GROW(array->objects, array->nr+1, array->alloc);

The semantics are weird. They never seemed so to me before, since it was
replacing some "grow by 1" areas where it is natural to assume that you
need just one spot more. But the way Junio commented it and tweaked it,
it can handle arbitrary growth (which is much better), but that means we
are overly conservative about when to grow.

Junio, patch is below (call-sites using bare 'nr' need to be 'nr+1', but
I will fix those up in a separate patch since they are in next and this
is in master).

-- >8 --
fix ALLOC_GROW off-by-one

The ALLOC_GROW macro will never let us fill the array completely,
instead allocating an extra chunk if that would be the case. This is
because the 'nr' argument was originally treated as "how much we do have
now" instead of "how much do we want". The latter makes much more
sense because you can grow by more than one item.

This off-by-one never resulted in an error because it meant we were
overly conservative about when to allocate. Any callers which passed
"how we have now" need to be updated, or they will fail to allocate
enough.

Signed-off-by: Jeff King <peff@peff.net>
---
 cache.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/cache.h b/cache.h
index c914c1c..ed83d92 100644
--- a/cache.h
+++ b/cache.h
@@ -234,7 +234,7 @@ extern void verify_non_filename(const char *prefix, const char *name);
  */
 #define ALLOC_GROW(x, nr, alloc) \
 	do { \
-		if ((nr) >= alloc) { \
+		if ((nr) > alloc) { \
 			if (alloc_nr(alloc) < (nr)) \
 				alloc = (nr); \
 			else \