git/alloc.c
SZEDER Gábor 4468d4435c object_as_type: initialize commit-graph-related fields of 'struct commit'
When the commit graph and generation numbers were introduced in
commits 177722b344 (commit: integrate commit graph with commit
parsing, 2018-04-10) and 83073cc994 (commit: add generation number to
struct commit, 2018-04-25), they tried to make sure that the
corresponding 'graph_pos' and 'generation' fields of 'struct commit'
are initialized conservatively, as if the commit were not included in
the commit-graph file.

Alas, initializing those fields only in alloc_commit_node() missed the
case when an object that happens to be a commit is first looked up via
lookup_unknown_object(), and is then later converted to a 'struct
commit' via the object_as_type() helper function (either calling it
directly, or as part of a subsequent lookup_commit() call).
Consequently, both of those fields incorrectly remain set to zero,
which means e.g. that the commit is present in and is the first entry
of the commit-graph file.  This will result in wrong timestamp, parent
and root tree hashes, if such a 'struct commit' instance is later
filled from the commit-graph.

Extract the initialization of 'struct commit's fields from
alloc_commit_node() into a helper function, and call it from
object_as_type() as well, to make sure that it properly initializes
the two commit-graph-related fields, too.  With this helper function
it is hopefully less likely that any new fields added to 'struct
commit' in the future would remain uninitialized.

With this change alloc_commit_index() won't have any remaining callers
outside of 'alloc.c', so mark it as static.

Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-01-27 16:55:57 -08:00

140 lines
3.2 KiB
C

/*
* alloc.c - specialized allocator for internal objects
*
* Copyright (C) 2006 Linus Torvalds
*
* The standard malloc/free wastes too much space for objects, partly because
* it maintains all the allocation infrastructure, but even more because it ends
* up with maximal alignment because it doesn't know what the object alignment
* for the new allocation is.
*/
#include "cache.h"
#include "object.h"
#include "blob.h"
#include "tree.h"
#include "commit.h"
#include "tag.h"
#include "alloc.h"
#define BLOCKING 1024
union any_object {
struct object object;
struct blob blob;
struct tree tree;
struct commit commit;
struct tag tag;
};
struct alloc_state {
int count; /* total number of nodes allocated */
int nr; /* number of nodes left in current allocation */
void *p; /* first free node in current allocation */
/* bookkeeping of allocations */
void **slabs;
int slab_nr, slab_alloc;
};
struct alloc_state *allocate_alloc_state(void)
{
return xcalloc(1, sizeof(struct alloc_state));
}
void clear_alloc_state(struct alloc_state *s)
{
while (s->slab_nr > 0) {
s->slab_nr--;
free(s->slabs[s->slab_nr]);
}
FREE_AND_NULL(s->slabs);
}
static inline void *alloc_node(struct alloc_state *s, size_t node_size)
{
void *ret;
if (!s->nr) {
s->nr = BLOCKING;
s->p = xmalloc(BLOCKING * node_size);
ALLOC_GROW(s->slabs, s->slab_nr + 1, s->slab_alloc);
s->slabs[s->slab_nr++] = s->p;
}
s->nr--;
s->count++;
ret = s->p;
s->p = (char *)s->p + node_size;
memset(ret, 0, node_size);
return ret;
}
void *alloc_blob_node(struct repository *r)
{
struct blob *b = alloc_node(r->parsed_objects->blob_state, sizeof(struct blob));
b->object.type = OBJ_BLOB;
return b;
}
void *alloc_tree_node(struct repository *r)
{
struct tree *t = alloc_node(r->parsed_objects->tree_state, sizeof(struct tree));
t->object.type = OBJ_TREE;
return t;
}
void *alloc_tag_node(struct repository *r)
{
struct tag *t = alloc_node(r->parsed_objects->tag_state, sizeof(struct tag));
t->object.type = OBJ_TAG;
return t;
}
void *alloc_object_node(struct repository *r)
{
struct object *obj = alloc_node(r->parsed_objects->object_state, sizeof(union any_object));
obj->type = OBJ_NONE;
return obj;
}
static unsigned int alloc_commit_index(struct repository *r)
{
return r->parsed_objects->commit_count++;
}
void init_commit_node(struct repository *r, struct commit *c)
{
c->object.type = OBJ_COMMIT;
c->index = alloc_commit_index(r);
c->graph_pos = COMMIT_NOT_FROM_GRAPH;
c->generation = GENERATION_NUMBER_INFINITY;
}
void *alloc_commit_node(struct repository *r)
{
struct commit *c = alloc_node(r->parsed_objects->commit_state, sizeof(struct commit));
init_commit_node(r, c);
return c;
}
static void report(const char *name, unsigned int count, size_t size)
{
fprintf(stderr, "%10s: %8u (%"PRIuMAX" kB)\n",
name, count, (uintmax_t) size);
}
#define REPORT(name, type) \
report(#name, r->parsed_objects->name##_state->count, \
r->parsed_objects->name##_state->count * sizeof(type) >> 10)
void alloc_report(struct repository *r)
{
REPORT(blob, struct blob);
REPORT(tree, struct tree);
REPORT(commit, struct commit);
REPORT(tag, struct tag);
REPORT(object, union any_object);
}