Re: fs/hfsplus/xattr.c: comparison of distinct pointer types lacks a cast

[Christian Kujau <lists@nerdbynature.de>]

On Sun, 25 May 2014 at 10:48, Geert Uytterhoeven wrote:
> "tmp" is "loff_t" which is "__kernel_loff_t", which is "long long", i.e. signed,
> while include/asm-generic/div64.h compares its type with "uint64_t".

Thanks for the explanation!

> As inode sizes are positive, it should be safe to change the type of "tmp"
> to "u64". Does that make the warning go away?

Yes, this helped! Compile-tested only:

 Signed-off-by: Christian Kujau <lists@nerdbynature.de>
      Fixed-by: Geert Uytterhoeven <geert@linux-m68k.org>

Commit a99b7069aab8fc3fb4f26d15795dc280b52e38b1 introduced do_div() to 
xattr.c and the warning below too.

As Geert remarked: "tmp" is "loff_t" which is "__kernel_loff_t", which
is "long long", i.e. signed, while include/asm-generic/div64.h compares
its type with "uint64_t". As inode sizes are positive, it should be safe 
to change the type of "tmp" to "u64". 

==============================
  CC [M]  fs/hfsplus/xattr_user.o
  CC [M]  fs/hfsplus/xattr_security.o
  CC [M]  fs/hfsplus/xattr.o
  CC [M]  fs/hfsplus/xattr_trusted.o
In file included from 
arch/powerpc/include/asm/div64.h:1:0,
                 from include/linux/kernel.h:124,
                 from include/asm-generic/bug.h:13,
                 from arch/powerpc/include/asm/bug.h:127,
                 from include/linux/bug.h:4,
                 from include/linux/thread_info.h:11,
                 from include/asm-generic/preempt.h:4,
                 from arch/powerpc/include/generated/asm/preempt.h:1,
                 from include/linux/preempt.h:18,
                 from include/linux/spinlock.h:50,
                 from include/linux/wait.h:8,
                 from include/linux/fs.h:6,
                 from fs/hfsplus/hfsplus_fs.h:19,
                 from fs/hfsplus/xattr.c:9:
fs/hfsplus/xattr.c: In function 
'hfsplus_init_header_node':
include/asm-generic/div64.h:43:28: warning: 
comparison of distinct pointer types lacks a cast [enabled by default]
  (void)(((typeof((n)) *)0) == ((uint64_t *)0)); \
                            ^
fs/hfsplus/xattr.c:86:2: note: in expansion of 
macro 'do_div'
  do_div(tmp, node_size);
  ^
  LD [M]  fs/hfsplus/hfsplus.o
==============================


diff --git a/fs/hfsplus/xattr.c b/fs/hfsplus/xattr.c
index 4e27edc..cd9ed4c 100644
--- a/fs/hfsplus/xattr.c
+++ b/fs/hfsplus/xattr.c
@@ -66,7 +66,7 @@ static void hfsplus_init_header_node(struct inode *attr_file,
 	char *bmp;
 	u32 used_nodes;
 	u32 used_bmp_bytes;
-	loff_t tmp;
+	u64 tmp;
 
 	hfs_dbg(ATTR_MOD, "init_hdr_attr_file: clump %u, node_size %u\n",
 				clump_size, node_size);



Thanks,
Christian.
-- 
BOFH excuse #388:

Bad user karma.