Re: [RFC] clang-format: outline the git project's coding style

[Junio C Hamano <gitster@pobox.com>]

Junio C Hamano <gitster@pobox.com> writes:

>>> > +# Insert a space after a cast
>>> > +# x = (int32) y;    not    x = (int32)y;
>>> > +SpaceAfterCStyleCast: true
>>> 
>>> Hmph, I thought we did the latter, i.e. cast sticks to the casted
>>> expression without SP.
>>
>> I've seen both and I wasn't sure which was the correct form to use.
>
> We do the latter because checkpatch.pl from the kernel project tells
> us to, I think.

Before I forget, there are some rules in checkpatch.pl that I
deliberately ignore while accepting patches from the list.  

I appreciate the tool for pointing out overlong lines, but I often
find them easier to read as-is than split into two lines, as the
ones the people send in real life rarely excessively exceed the
80-col limit.  We also use things like SHA_CTX that trigger "avoid
camelcase", which I also ignore.

One thing we probably should standardize is the way the width of
bitfields in struct is specified.  I think checkpatch.pl wants to do

	struct {
		unsigned int three_bits : 3;
	};

with SP around the colon, but our codebase does not always have the
spaces there, and I see no technical reason not to follow suit, as
long as we are following most of what checkpatch.pl wants us to do.

By the way, I do not recall seeing a rule about this in your clang
format rules.  Can we spell it out in there?

I also see this:

    WARNING: __printf(string-index, first-to-check) is preferred over
    __attribute__((format(printf, string-index, first-to-check)))

but I think it is specific to the kernel source (the macro is
defined in include/linux/compiler-gcc.h and expands to the latter),
so I also ignore it.

checkpatch.pl also warns a SP immediately before HT, which I do pay
attention to, as well as trailing whitespaces.  If clang-format can
be told to check that, I think we would want to have such a rule.

For a reference, here is a sample set of changes to cache.h to
squelch most of the warnings and errors checkpatch.pl points out
that I do not ignore.

 cache.h | 30 +++++++++++++++---------------
 1 file changed, 15 insertions(+), 15 deletions(-)

diff --git a/cache.h b/cache.h
index 4e390e6af8..dec807b3b0 100644
--- a/cache.h
+++ b/cache.h
@@ -25,7 +25,7 @@
 #define platform_SHA_CTX	SHA_CTX
 #define platform_SHA1_Init	SHA1_Init
 #define platform_SHA1_Update	SHA1_Update
-#define platform_SHA1_Final    	SHA1_Final
+#define platform_SHA1_Final	SHA1_Final
 #endif
 
 #define git_SHA_CTX		platform_SHA_CTX
@@ -260,7 +260,7 @@ static inline void copy_cache_entry(struct cache_entry *dst,
 
 static inline unsigned create_ce_flags(unsigned stage)
 {
-	return (stage << CE_STAGESHIFT);
+	return stage << CE_STAGESHIFT;
 }
 
 #define ce_namelen(ce) ((ce)->ce_namelen)
@@ -317,7 +317,7 @@ static inline unsigned int canon_mode(unsigned int mode)
 	return S_IFGITLINK;
 }
 
-#define cache_entry_size(len) (offsetof(struct cache_entry,name) + (len) + 1)
+#define cache_entry_size(len) (offsetof(struct cache_entry, name) + (len) + 1)
 
 #define SOMETHING_CHANGED	(1 << 0) /* unclassified changes go here */
 #define CE_ENTRY_CHANGED	(1 << 1)
@@ -373,7 +373,7 @@ extern void free_name_hash(struct index_state *istate);
 #define read_cache_unmerged() read_index_unmerged(&the_index)
 #define discard_cache() discard_index(&the_index)
 #define unmerged_cache() unmerged_index(&the_index)
-#define cache_name_pos(name, namelen) index_name_pos(&the_index,(name),(namelen))
+#define cache_name_pos(name, namelen) index_name_pos(&the_index, (name), (namelen))
 #define add_cache_entry(ce, option) add_index_entry(&the_index, (ce), (option))
 #define rename_cache_entry_at(pos, new_name) rename_index_entry_at(&the_index, (pos), (new_name))
 #define remove_cache_entry_at(pos) remove_index_entry_at(&the_index, (pos))
@@ -1483,10 +1483,10 @@ struct checkout {
 	const char *base_dir;
 	int base_dir_len;
 	struct delayed_checkout *delayed_checkout;
-	unsigned force:1,
-		 quiet:1,
-		 not_new:1,
-		 refresh_cache:1;
+	unsigned force : 1,
+		 quiet : 1,
+		 not_new : 1,
+		 refresh_cache : 1;
 };
 #define CHECKOUT_INIT { NULL, "" }
 
@@ -1534,7 +1534,7 @@ extern struct alternate_object_database {
 	char path[FLEX_ARRAY];
 } *alt_odb_list;
 extern void prepare_alt_odb(void);
-extern void read_info_alternates(const char * relative_base, int depth);
+extern void read_info_alternates(const char *relative_base, int depth);
 extern char *compute_alternate_path(const char *path, struct strbuf *err);
 typedef int alt_odb_fn(struct alternate_object_database *, void *);
 extern int foreach_alt_odb(alt_odb_fn, void*);
@@ -1587,10 +1587,10 @@ extern struct packed_git {
 	int index_version;
 	time_t mtime;
 	int pack_fd;
-	unsigned pack_local:1,
-		 pack_keep:1,
-		 freshened:1,
-		 do_not_close:1;
+	unsigned pack_local : 1,
+		 pack_keep : 1,
+		 freshened : 1,
+		 do_not_close : 1;
 	unsigned char sha1[20];
 	struct revindex_entry *revindex;
 	/* something like ".git/objects/pack/xxxxx.pack" */
@@ -1767,10 +1767,10 @@ struct object_info {
 	union {
 		/*
 		 * struct {
-		 * 	... Nothing to expose in this case
+		 *	... Nothing to expose in this case
 		 * } cached;
 		 * struct {
-		 * 	... Nothing to expose in this case
+		 *	... Nothing to expose in this case
 		 * } loose;
 		 */
 		struct {