[PATCH] index-pack: never prune base_cache.

[Pierre Habouzit <madcoder@debian.org>]

It may belong to something (stdin) that is consumed.

Signed-off-by: Pierre Habouzit <madcoder@debian.org>
---

    On Wed, Jul 23, 2008 at 12:00:45PM +0000, Björn Steinbrink wrote:
    > On 2008.07.23 12:37:00 +0100, Johannes Schindelin wrote:
    > > Hi,
    > > 
    > > Well, I cannot.  However, I get some pread issue on i686.  To be nice to 
    > > kernel.org, I downloaded the pack in question:
    > > 
    > > 	http://pacific.mpi-cbg.de/git/thin-pack.pack
    > > 
    > > You should be able to reproduce the behavior by piping this into
    > > 
    > > git-index-pack --stdin -v --fix-thin --keep=fetch-pack --pack_header=2,263
    > 
    > OK, that gave me a seemingly sane backtrace. What seems to happen (AFA
    > my limited knowledge tells me):
    > 
    > In fix_unresolved_deltas, we read base_obj from an existing pack, other
    > than the one we're reading. We then link that object to the base cache. 
    > 
    > Then in resolve_delta, we create the "result" base_data object and link
    > that one, too. Now this triggers the pruning, and because the cache is
    > so small, we prune the object that we read from the existing pack! Fast
    > forward a few function calls, we end up in get_base_data trying to
    > re-read the data for that object, but this time from the pack that we
    > got on stdin. And boom it goes.
    > 
    > Does that make any sense to you?

      Yes, that's obvious, the pack that we read from stdin is consumed, we
    should *NEVER* prune base_cache. And indeed that little patch works for
    me.

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

diff --git a/index-pack.c b/index-pack.c
index ac20a46..eb81ed4 100644
--- a/index-pack.c
+++ b/index-pack.c
@@ -227,7 +227,7 @@ static void prune_base_data(struct base_data *retain)
 	for (b = base_cache;
 	     base_cache_used > delta_base_cache_limit && b;
 	     b = b->child) {
-		if (b->data && b != retain) {
+		if (b != base_cache && b->data && b != retain) {
 			free(b->data);
 			b->data = NULL;
 			base_cache_used -= b->size;
-- 
1.6.0.rc0.155.ga0442.dirty