[PATCH] read-cache.c: fix a sparse warning

[Ramsay Jones <ramsay@ramsayjones.plus.com>]

At one time, the POSIX standard required the type used to represent
a thread handle (pthread_t) be an arithmetic type. This is no longer
the case, probably because different platforms used to regularly
ignore that requirement.  For example, on cygwin a pthread_t is a
pointer to a structure (a quite common choice), whereas on Linux it
is defined as an 'unsigned long int'.

On cygwin, but not on Linux, 'sparse' currently complains about an
initialiser used on a 'struct load_index_extensions' variable, whose
first field may be a pthread handle (if not compiled with NO_PTHREADS
set).

In order to fix the warning, move the (conditional) pthread field to
the end of the struct and change the initialiser to use a NULL, since
the new (unconditional) first field is a pointer type.

Signed-off-by: Ramsay Jones <ramsay@ramsayjones.plus.com>
---

Hi Ben,

If you need to re-roll your 'bp/read-cache-parallel' branch, could you
please squash this into the relevant patch (commit a090af334,
"read-cache: load cache extensions on a worker thread", 2018-09-12).

Thanks.

ATB,
Ramsay Jones

 read-cache.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/read-cache.c b/read-cache.c
index b27dc01696..6254291742 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -1908,13 +1908,13 @@ static void write_eoie_extension(struct strbuf *sb, git_hash_ctx *eoie_context,
 
 struct load_index_extensions
 {
-#ifndef NO_PTHREADS
-	pthread_t pthread;
-#endif
 	struct index_state *istate;
 	const char *mmap;
 	size_t mmap_size;
 	unsigned long src_offset;
+#ifndef NO_PTHREADS
+	pthread_t pthread;
+#endif
 };
 
 static void *load_index_extensions(void *data)
@@ -2145,7 +2145,7 @@ int do_read_index(struct index_state *istate, const char *path, int must_exist)
 	const struct cache_header *hdr;
 	const char *mmap;
 	size_t mmap_size;
-	struct load_index_extensions p = { 0 };
+	struct load_index_extensions p = { NULL };
 	unsigned long extension_offset = 0;
 #ifndef NO_PTHREADS
 	int cpus, nr_threads;
-- 
2.19.0