[PATCH] Use MAP_FAILED instead of double cast

[Pavel Roskin <proski@gnu.org>]

Hello!

I have found some really ugly code to used to check the result of
mmap():

if (-1 == (int)(long)map)
	return;

Double cast almost always indicates that something fishy is going on.
Indeed, mmap() could (in theory) return 0xffffffff on a 64-bit platform,
and that would be misinterpreted as a failure.

There is a preprocessor symbol MAP_FAILED that should be used instead.
It's used already in some places, so let's use it consistently.

Signed-off-by: Pavel Roskin <proski@gnu.org>

diff --git a/diffcore-order.c b/diffcore-order.c
--- a/diffcore-order.c
+++ b/diffcore-order.c
@@ -28,7 +28,7 @@ static void prepare_order(const char *or
 	}
 	map = mmap(NULL, st.st_size, PROT_READ|PROT_WRITE, MAP_PRIVATE, fd, 0);
 	close(fd);
-	if (-1 == (int)(long)map)
+	if (map == MAP_FAILED)
 		return;
 	endp = map + st.st_size;
 	for (pass = 0; pass < 2; pass++) {
diff --git a/local-pull.c b/local-pull.c
--- a/local-pull.c
+++ b/local-pull.c
@@ -54,7 +54,7 @@ int fetch(unsigned char *sha1)
 		}
 		map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, ifd, 0);
 		close(ifd);
-		if (-1 == (int)(long)map) {
+		if (map == MAP_FAILED) {
 			fprintf(stderr, "cannot mmap %s\n", filename);
 			return -1;
 		}
diff --git a/read-cache.c b/read-cache.c
--- a/read-cache.c
+++ b/read-cache.c
@@ -376,7 +376,7 @@ int read_cache(void)
 			map = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
 	}
 	close(fd);
-	if (-1 == (int)(long)map)
+	if (map == MAP_FAILED)
 		return error("mmap failed");
 
 	hdr = map;
diff --git a/sha1_file.c b/sha1_file.c
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -507,7 +507,7 @@ static void *map_sha1_file_internal(cons
 	}
 	map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
 	close(fd);
-	if (-1 == (int)(long)map)
+	if (map == MAP_FAILED)
 		return NULL;
 	*size = st.st_size;
 	return map;
@@ -1293,7 +1293,7 @@ int index_fd(unsigned char *sha1, int fd
 	if (size)
 		buf = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
 	close(fd);
-	if ((int)(long)buf == -1)
+	if (buf == MAP_FAILED)
 		return -1;
 
 	ret = write_sha1_file(buf, size, "blob", sha1);


-- 
Regards,
Pavel Roskin