Re: [PATCH v4 4/6] coccinelle: add a rule to make "expression" code use FREE_AND_NULL()

["René Scharfe" <l.s.r@web.de>]

Am 28.06.2017 um 23:39 schrieb Ævar Arnfjörð Bjarmason:
> 
> On Sun, Jun 25 2017, René Scharfe jotted:
> 
>> Am 16.06.2017 um 21:43 schrieb Junio C Hamano:
>>> Ævar Arnfjörð Bjarmason  <avarab@gmail.com> writes:
>>>
>>>> A follow-up to the existing "type" rule added in an earlier
>>>> change. This catches some occurrences that are missed by the previous
>>>> rule.
>>>>
>>>> Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
>>>> ---
>>>
>>> Hmph, I wonder if the "type" thing is really needed.  Over there,
>>> "ptr" is an expression and we can find "free(ptr); ptr = NULL" with
>>> the rule in this patch already, no?
>>
>> Indeed.  How about this on top of master?
>>
>> -- >8 --
>> Subject: [PATCH] coccinelle: polish FREE_AND_NULL rules
>>
>> There are two rules for using FREE_AND_NULL in free.cocci, one for
>> pointer types and one for expressions.  Both cause coccinelle to remove
>> empty lines and even newline characters between replacements for some
>> reason; consecutive "free(x);/x=NULL;" sequences end up as multiple
>> FREE_AND_NULL calls on the same time.
>>
>> Remove the type rule, as the expression rule already covers it, and
>> rearrange the lines of the latter to place the addition of FREE_AND_NULL
>> between the removals, which causes coccinelle to leave surrounding
>> whitespace untouched.
>>
>> Signed-off-by: Rene Scharfe <l.s.r@web.de>
>> ---
>>   contrib/coccinelle/free.cocci | 10 +---------
>>   1 file changed, 1 insertion(+), 9 deletions(-)
>>
>> diff --git a/contrib/coccinelle/free.cocci b/contrib/coccinelle/free.cocci
>> index f2d97e755b..4490069df9 100644
>> --- a/contrib/coccinelle/free.cocci
>> +++ b/contrib/coccinelle/free.cocci
>> @@ -11,16 +11,8 @@ expression E;
>>     free(E);
>>
>>   @@
>> -type T;
>> -T *ptr;
>> -@@
>> -- free(ptr);
>> -- ptr = NULL;
>> -+ FREE_AND_NULL(ptr);
>> -
>> -@@
>>   expression E;
>>   @@
>>   - free(E);
>> -- E = NULL;
>>   + FREE_AND_NULL(E);
>> +- E = NULL;
> 
> Late reply, sorry. What version of coccinelle are you running? I have
> 1.0.4 (from Debian) and can't get this to produce the same results as
> what I have.
> 
> On top of next, I did:
> 
>          Revert "*.[ch] refactoring: make use of the FREE_AND_NULL() macro"
>          Revert "coccinelle: make use of the "expression" FREE_AND_NULL() rule"
>          Revert "coccinelle: make use of the "type" FREE_AND_NULL() rule"
> 
> And then generated the patch as usual with `make coccicheck`, and
> applied it. This has your change.
> 
> I then re-applied the manual "*.[ch] refactoring" changes
> 
> This results in this diff with next:
> 
>      $ git diff --stat origin/next.. -- '*.[ch]'
>       builtin/am.c             |  3 ++-
>       builtin/clean.c          |  6 ++++--
>       builtin/config.c         |  6 ++++--
>       builtin/index-pack.c     |  6 ++++--
>       builtin/pack-objects.c   | 12 ++++++++----
>       builtin/unpack-objects.c |  3 ++-
>       fast-import.c            |  6 ++++--
>       http-push.c              | 24 ++++++++++++++++--------
>       http.c                   | 15 ++++++++++-----
>       imap-send.c              |  3 ++-
>       ref-filter.c             |  3 ++-
>       refs/files-backend.c     |  3 ++-
>       remote-testsvn.c         |  3 ++-
>       sequencer.c              |  3 ++-
>       sha1-array.c             |  3 ++-
>       sha1_file.c              |  3 ++-
>       transport-helper.c       | 27 ++++++++++++++++++---------
>       transport.c              |  3 ++-
>       tree-diff.c              |  6 ++++--
>       tree.c                   |  3 ++-
>       20 files changed, 94 insertions(+), 47 deletions(-)
> 
> These are all cases where we now miss things that should use
> FREE_AND_NULL(), e.g.:
> 
>      diff --git a/builtin/am.c b/builtin/am.c
>      index c973bd96dc..2f89338ed7 100644
>      --- a/builtin/am.c
>      +++ b/builtin/am.c
>      @@ -484,7 +484,8 @@ static int run_applypatch_msg_hook(struct am_state *state)
>              ret = run_hook_le(NULL, "applypatch-msg", am_path(state, "final-commit"), NULL);
> 
>              if (!ret) {
>      -               FREE_AND_NULL(state->msg);
>      +               free(state->msg);
>      +               state->msg = NULL;
>                      if (read_commit_msg(state) < 0)
>                              die(_("'%s' was deleted by the applypatch-msg hook"),
>                                      am_path(state, "final-commit"));
> 
> So it looks to me like removing the "type T" rule breaks a lot of
> things, but that the change you made to the expression rule is good, and
> we should do that for the "type" rule as well. Your commit says the
> "expression rule already covers it", but this doesn't seem to be the
> case at all.
> 
> As an aside: Junio, did you mean to apply f8bb4631fb to next this way?
> Looks like a mis-applied scissor commit.

I can't reproduce that strange result with master, but get a scissors
line into the commit message as well.  The diff at the end looks
reasonable (contains just the manual stuff).  Here's what I did:

$ uname -a
Linux debian 4.9.0-3-amd64 #1 SMP Debian 4.9.30-2 (2017-06-12) x86_64 GNU/Linux

$ spatch -version
spatch version 1.0.4 with Python support and with PCRE support

$ git checkout -b cocci-free-null origin/master
Branch cocci-free-null set up to track remote branch master from origin.
Switched to a new branch 'cocci-free-null'

$ git am
# pasted my email
Applying: coccinelle: add a rule to make "expression" code use FREE_AND_NULL()
# results in commit message with scissor line, interesting..

$ git revert --no-edit 88ce3ef636 e140f7afdd 6a83d90207
[cocci-free-null b50d5eca5f] Revert "*.[ch] refactoring: make use of the FREE_AND_NULL() macro"
 12 files changed, 49 insertions(+), 23 deletions(-)
[cocci-free-null cf9072ce4e] Revert "coccinelle: make use of the "expression" FREE_AND_NULL() rule"
 2 files changed, 4 insertions(+), 2 deletions(-)
[cocci-free-null 97675d4dc2] Revert "coccinelle: make use of the "type" FREE_AND_NULL() rule"
 37 files changed, 142 insertions(+), 71 deletions(-)

$ make contrib/coccinelle/free.cocci.patch
GIT_VERSION = 2.13.2.537.g97675d4dc2
     SPATCH contrib/coccinelle/free.cocci
     SPATCH result: contrib/coccinelle/free.cocci.patch

$ patch -p0 <contrib/coccinelle/free.cocci.patch
patching file alias.c
patching file apply.c
patching file attr.c
patching file blame.c
patching file branch.c
patching file commit.c
patching file config.c
patching file credential.c
patching file diffcore-rename.c
patching file diff-lib.c
patching file diff.c
patching file dir.c
patching file grep.c
patching file line-log.c
patching file ll-merge.c
patching file mailinfo.c
patching file object.c
patching file pathspec.c
patching file read-cache.c
patching file refs/files-backend.c
patching file ref-filter.c
patching file sequencer.c
patching file sha1-array.c
patching file sha1_file.c
patching file transport.c
patching file transport-helper.c
patching file tree-diff.c
patching file tree.c
patching file builtin/am.c
patching file builtin/clean.c
patching file builtin/config.c
patching file builtin/index-pack.c
patching file builtin/pack-objects.c
patching file builtin/unpack-objects.c
patching file fast-import.c
patching file imap-send.c
patching file remote-testsvn.c
patching file http-push.c
patching file http.c

$ git diff HEAD^^^
diff --git a/builtin/am.c b/builtin/am.c
index c973bd96dc..eb24eb7b08 100644
--- a/builtin/am.c
+++ b/builtin/am.c
@@ -1074,8 +1074,11 @@ static void am_next(struct am_state *state)
 	struct object_id head;
 
 	FREE_AND_NULL(state->author_name);
+
 	FREE_AND_NULL(state->author_email);
+
 	FREE_AND_NULL(state->author_date);
+
 	FREE_AND_NULL(state->msg);
 	state->msg_len = 0;
 
diff --git a/builtin/worktree.c b/builtin/worktree.c
index c98e2ce5f5..0c5476ee9d 100644
--- a/builtin/worktree.c
+++ b/builtin/worktree.c
@@ -300,8 +300,10 @@ static int add_worktree(const char *path, const char *refname,
 	}
 
 	is_junk = 0;
-	FREE_AND_NULL(junk_work_tree);
-	FREE_AND_NULL(junk_git_dir);
+	free(junk_work_tree);
+	free(junk_git_dir);
+	junk_work_tree = NULL;
+	junk_git_dir = NULL;
 
 done:
 	if (ret || !opts->keep_locked) {
diff --git a/commit-slab.h b/commit-slab.h
index 333d81e370..42d16dcded 100644
--- a/commit-slab.h
+++ b/commit-slab.h
@@ -82,7 +82,8 @@ static MAYBE_UNUSED void clear_ ##slabname(struct slabname *s)		\
 	for (i = 0; i < s->slab_count; i++)				\
 		free(s->slab[i]);					\
 	s->slab_count = 0;						\
-	FREE_AND_NULL(s->slab);						\
+	free(s->slab);							\
+	s->slab = NULL;							\
 }									\
 									\
 static MAYBE_UNUSED elemtype *slabname## _at_peek(struct slabname *s,	\
diff --git a/gpg-interface.c b/gpg-interface.c
index d936f3a32f..8ab32df457 100644
--- a/gpg-interface.c
+++ b/gpg-interface.c
@@ -14,11 +14,16 @@ static const char *gpg_program = "gpg";
 
 void signature_check_clear(struct signature_check *sigc)
 {
-	FREE_AND_NULL(sigc->payload);
-	FREE_AND_NULL(sigc->gpg_output);
-	FREE_AND_NULL(sigc->gpg_status);
-	FREE_AND_NULL(sigc->signer);
-	FREE_AND_NULL(sigc->key);
+	free(sigc->payload);
+	free(sigc->gpg_output);
+	free(sigc->gpg_status);
+	free(sigc->signer);
+	free(sigc->key);
+	sigc->payload = NULL;
+	sigc->gpg_output = NULL;
+	sigc->gpg_status = NULL;
+	sigc->signer = NULL;
+	sigc->key = NULL;
 }
 
 static struct {
diff --git a/help.c b/help.c
index 88a3aeaeb9..5af5319caf 100644
--- a/help.c
+++ b/help.c
@@ -269,8 +269,9 @@ static void add_cmd_list(struct cmdnames *cmds, struct cmdnames *old)
 
 	for (i = 0; i < old->cnt; i++)
 		cmds->names[cmds->cnt++] = old->names[i];
-	FREE_AND_NULL(old->names);
+	free(old->names);
 	old->cnt = 0;
+	old->names = NULL;
 }
 
 /* An empirically derived magic number */
diff --git a/line-log.c b/line-log.c
index ab0709f9ae..f225447ebb 100644
--- a/line-log.c
+++ b/line-log.c
@@ -34,8 +34,9 @@ void range_set_init(struct range_set *rs, size_t prealloc)
 
 void range_set_release(struct range_set *rs)
 {
-	FREE_AND_NULL(rs->ranges);
+	free(rs->ranges);
 	rs->alloc = rs->nr = 0;
+	rs->ranges = NULL;
 }
 
 /* dst must be uninitialized! */
diff --git a/prio-queue.c b/prio-queue.c
index 126d096727..fc3860fdcb 100644
--- a/prio-queue.c
+++ b/prio-queue.c
@@ -27,9 +27,10 @@ void prio_queue_reverse(struct prio_queue *queue)
 
 void clear_prio_queue(struct prio_queue *queue)
 {
-	FREE_AND_NULL(queue->array);
+	free(queue->array);
 	queue->nr = 0;
 	queue->alloc = 0;
+	queue->array = NULL;
 	queue->insertion_ctr = 0;
 }
 
diff --git a/refs/ref-cache.c b/refs/ref-cache.c
index 76bb723c86..af2fcb2c12 100644
--- a/refs/ref-cache.c
+++ b/refs/ref-cache.c
@@ -82,8 +82,9 @@ static void clear_ref_dir(struct ref_dir *dir)
 	int i;
 	for (i = 0; i < dir->nr; i++)
 		free_ref_entry(dir->entries[i]);
-	FREE_AND_NULL(dir->entries);
+	free(dir->entries);
 	dir->sorted = dir->nr = dir->alloc = 0;
+	dir->entries = NULL;
 }
 
 struct ref_entry *create_dir_entry(struct ref_cache *cache,
diff --git a/rerere.c b/rerere.c
index 70634d456c..829b3b0f08 100644
--- a/rerere.c
+++ b/rerere.c
@@ -40,8 +40,9 @@ static void free_rerere_dirs(void)
 		free(rerere_dir[i]->status);
 		free(rerere_dir[i]);
 	}
-	FREE_AND_NULL(rerere_dir);
+	free(rerere_dir);
 	rerere_dir_nr = rerere_dir_alloc = 0;
+	rerere_dir = NULL;
 }
 
 static void free_rerere_id(struct string_list_item *item)
diff --git a/split-index.c b/split-index.c
index 83e39ec8d7..f519e60f87 100644
--- a/split-index.c
+++ b/split-index.c
@@ -167,9 +167,10 @@ void merge_base_index(struct index_state *istate)
 
 	ewah_free(si->delete_bitmap);
 	ewah_free(si->replace_bitmap);
-	FREE_AND_NULL(si->saved_cache);
+	free(si->saved_cache);
 	si->delete_bitmap  = NULL;
 	si->replace_bitmap = NULL;
+	si->saved_cache	   = NULL;
 	si->saved_cache_nr = 0;
 }