From a133c40b23c80ed77cfe077213a45af67be28f74 Mon Sep 17 00:00:00 2001 From: Nguyễn Thái Ngọc Duy Date: Tue, 16 Apr 2019 16:33:18 +0700 Subject: commit.cocci: refactor code, avoid double rewrite MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit "maybe" pointer in 'struct commit' is tricky because it can be lazily initialized to take advantage of commit-graph if available. This makes it not safe to access directly. This leads to a rule in commit.cocci to rewrite 'x->maybe_tree' to 'get_commit_tree(x)'. But that rule alone could lead to incorrectly rewrite assignments, e.g. from x->maybe_tree = yes to get_commit_tree(x) = yes Because of this we have a second rule to revert this effect. Szeder found out that we could do better by performing the assignment rewrite rule first, then the remaining is read-only access and handled by the current first rule. For this to work, we need to transform "x->maybe_tree = y" to something that does NOT contain "x->maybe_tree" to avoid the original first rule. This is where set_commit_tree() comes in. Helped-by: SZEDER Gábor Helped-by: Johannes Schindelin Signed-off-by: Nguyễn Thái Ngọc Duy Signed-off-by: Junio C Hamano --- commit.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) (limited to 'commit.c') diff --git a/commit.c b/commit.c index a5333c7ac6..043ba64f17 100644 --- a/commit.c +++ b/commit.c @@ -340,6 +340,11 @@ void free_commit_buffer(struct parsed_object_pool *pool, struct commit *commit) } } +static inline void set_commit_tree(struct commit *c, struct tree *t) +{ + c->maybe_tree = t; +} + struct tree *get_commit_tree(const struct commit *commit) { if (commit->maybe_tree || !commit->object.parsed) @@ -358,7 +363,7 @@ struct object_id *get_commit_tree_oid(const struct commit *commit) void release_commit_memory(struct parsed_object_pool *pool, struct commit *c) { - c->maybe_tree = NULL; + set_commit_tree(c, NULL); c->index = 0; free_commit_buffer(pool, c); free_commit_list(c->parents); @@ -406,7 +411,7 @@ int parse_commit_buffer(struct repository *r, struct commit *item, const void *b if (get_oid_hex(bufptr + 5, &parent) < 0) return error("bad tree pointer in commit %s", oid_to_hex(&item->object.oid)); - item->maybe_tree = lookup_tree(r, &parent); + set_commit_tree(item, lookup_tree(r, &parent)); bufptr += tree_entry_len + 1; /* "tree " + "hex sha1" + "\n" */ pptr = &item->parents; -- cgit v1.2.3 From 301b8c7f405d3cd4f32b14bd336ac8c0400d9382 Mon Sep 17 00:00:00 2001 From: Nguyễn Thái Ngọc Duy Date: Tue, 16 Apr 2019 16:33:19 +0700 Subject: commit.c: add repo_get_commit_tree() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Remove the implicit dependency on the_repository in this function. It will be used in sha1-name.c functions when they are updated to take any 'struct repository'. get_commit_tree() remains as a compat wrapper, to be slowly replaced later. Any access to "maybe_tree" field directly will result in _broken_ code after running through commit.cocci because we can't know what is the right repository to use. the_repository would be correct most of the time. But we're relying less and less on the_repository and that assumption may no longer be true. The transformation now is more of a poor man replacement for a C++ compiler catching access to private fields. Signed-off-by: Nguyễn Thái Ngọc Duy Signed-off-by: Junio C Hamano --- commit.c | 5 +++-- commit.h | 5 +++-- contrib/coccinelle/commit.cocci | 6 +++--- 3 files changed, 9 insertions(+), 7 deletions(-) (limited to 'commit.c') diff --git a/commit.c b/commit.c index 043ba64f17..a9e74647dc 100644 --- a/commit.c +++ b/commit.c @@ -345,7 +345,8 @@ static inline void set_commit_tree(struct commit *c, struct tree *t) c->maybe_tree = t; } -struct tree *get_commit_tree(const struct commit *commit) +struct tree *repo_get_commit_tree(struct repository *r, + const struct commit *commit) { if (commit->maybe_tree || !commit->object.parsed) return commit->maybe_tree; @@ -353,7 +354,7 @@ struct tree *get_commit_tree(const struct commit *commit) if (commit->graph_pos == COMMIT_NOT_FROM_GRAPH) BUG("commit has NULL tree, but was not loaded from commit-graph"); - return get_commit_tree_in_graph(the_repository, commit); + return get_commit_tree_in_graph(r, commit); } struct object_id *get_commit_tree_oid(const struct commit *commit) diff --git a/commit.h b/commit.h index 42728c2906..f1aa4c0472 100644 --- a/commit.h +++ b/commit.h @@ -32,7 +32,7 @@ struct commit { /* * If the commit is loaded from the commit-graph file, then this - * member may be NULL. Only access it through get_commit_tree() + * member may be NULL. Only access it through repo_get_commit_tree() * or get_commit_tree_oid(). */ struct tree *maybe_tree; @@ -143,7 +143,8 @@ void repo_unuse_commit_buffer(struct repository *r, */ void free_commit_buffer(struct parsed_object_pool *pool, struct commit *); -struct tree *get_commit_tree(const struct commit *); +struct tree *repo_get_commit_tree(struct repository *, const struct commit *); +#define get_commit_tree(c) repo_get_commit_tree(the_repository, c) struct object_id *get_commit_tree_oid(const struct commit *); /* diff --git a/contrib/coccinelle/commit.cocci b/contrib/coccinelle/commit.cocci index 663658a127..d03453341e 100644 --- a/contrib/coccinelle/commit.cocci +++ b/contrib/coccinelle/commit.cocci @@ -23,12 +23,12 @@ expression s; // These excluded functions must access c->maybe_tree direcly. // Note that if c->maybe_tree is written somewhere outside of these // functions, then the recommended transformation will be bogus with -// get_commit_tree() on the LHS. +// repo_get_commit_tree() on the LHS. @@ -identifier f !~ "^(get_commit_tree|get_commit_tree_in_graph_one|load_tree_for_commit|set_commit_tree)$"; +identifier f !~ "^(repo_get_commit_tree|get_commit_tree_in_graph_one|load_tree_for_commit|set_commit_tree)$"; expression c; @@ f(...) {<... - c->maybe_tree -+ get_commit_tree(c) ++ repo_get_commit_tree(specify_the_right_repo_here, c) ...>} -- cgit v1.2.3