[PATCH] CRED: fix compilation warning in function 'get_cred'

[PATCH] CRED: fix compilation warning in function 'get_cred'

[Hannes Eder]

Fix to following warning by introducing a temporary variable:

include/linux/cred.h: In function 'get_cred':
include/linux/cred.h:187: warning: passing argument 1 of
'get_new_cred' discards qualifiers from pointer target type

Signed-off-by: Hannes Eder <hannes@hanneseder.net>
---
With -O2 the same code as for the original function is generated.

 include/linux/cred.h |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/include/linux/cred.h b/include/linux/cred.h
index 26c1ab1..2ab8cf7 100644
--- a/include/linux/cred.h
+++ b/include/linux/cred.h
@@ -184,7 +184,8 @@ static inline struct cred *get_new_cred(struct cred *cred)
  */
 static inline const struct cred *get_cred(const struct cred *cred)
 {
-	return get_new_cred((struct cred *) cred);
+	struct cred *non_const_cred = (struct cred *) cred;
+	return get_new_cred(non_const_cred);
 }

 /**

[PATCH] CRED: fix compilation warning in function 'get_cred'

[Hannes Eder]

Fix to following warning by introducing a temporary variable:

include/linux/cred.h: In function 'get_cred':
include/linux/cred.h:187: warning: passing argument 1 of
'get_new_cred' discards qualifiers from pointer target type

Signed-off-by: Hannes Eder <hannes@hanneseder.net>
---
With -O2 the same code as for the original function is generated.

 include/linux/cred.h |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/include/linux/cred.h b/include/linux/cred.h
index 26c1ab1..2ab8cf7 100644
--- a/include/linux/cred.h
+++ b/include/linux/cred.h
@@ -184,7 +184,8 @@ static inline struct cred *get_new_cred(struct cred *cred)
  */
 static inline const struct cred *get_cred(const struct cred *cred)
 {
-	return get_new_cred((struct cred *) cred);
+	struct cred *non_const_cred = (struct cred *) cred;
+	return get_new_cred(non_const_cred);
 }

 /**

Re: [PATCH] CRED: fix compilation warning in function 'get_cred'

[David Howells]

Hannes Eder <hannes@hanneseder.net> wrote:

> Fix to following warning by introducing a temporary variable:
> 
> include/linux/cred.h: In function 'get_cred':
> include/linux/cred.h:187: warning: passing argument 1 of
> 'get_new_cred' discards qualifiers from pointer target type

Interesting.  I believe that's a compiler bug.  Explicitly casting away the
const should avoid this warning.

David

Re: [PATCH] CRED: fix compilation warning in function 'get_cred'

[Hannes Eder]

On Thu, Nov 20, 2008 at 11:19 PM, David Howells <dhowells@redhat.com> wrote:
> Hannes Eder <hannes@hanneseder.net> wrote:
>
>> Fix to following warning by introducing a temporary variable:
>>
>> include/linux/cred.h: In function 'get_cred':
>> include/linux/cred.h:187: warning: passing argument 1 of
>> 'get_new_cred' discards qualifiers from pointer target type
>
> Interesting.  I believe that's a compiler bug.  Explicitly casting away the
> const should avoid this warning.

Strange. I think you are right, looks like a compiler bug.  I am using
gcc (GCC) 4.2.4 (Ubuntu 4.2.4-1ubuntu3).  Compiling the following code
snippet does not yield a spurious warning:

struct foo {
	int a;
};

static inline struct foo *bar(struct foo *foo)
{
	foo->a++;
	return foo;
}

static inline const struct foo *bar2(const struct foo *foo)
{
	return bar((struct foo*)foo);
}

What do you suggest, report this as a gcc bug?

-Hannes

Re: [PATCH] CRED: fix compilation warning in function 'get_cred'

[Hannes Eder]

On Thu, Nov 20, 2008 at 11:19 PM, David Howells <dhowells@redhat.com> wrote:
> Hannes Eder <hannes@hanneseder.net> wrote:
>
>> Fix to following warning by introducing a temporary variable:
>>
>> include/linux/cred.h: In function 'get_cred':
>> include/linux/cred.h:187: warning: passing argument 1 of
>> 'get_new_cred' discards qualifiers from pointer target type
>
> Interesting.  I believe that's a compiler bug.  Explicitly casting away the
> const should avoid this warning.

Strange. I think you are right, looks like a compiler bug.  I am using
gcc (GCC) 4.2.4 (Ubuntu 4.2.4-1ubuntu3).  Compiling the following code
snippet does not yield a spurious warning:

struct foo {
	int a;
};

static inline struct foo *bar(struct foo *foo)
{
	foo->a++;
	return foo;
}

static inline const struct foo *bar2(const struct foo *foo)
{
	return bar((struct foo*)foo);
}

What do you suggest, report this as a gcc bug?

-Hannes

Re: [PATCH] CRED: fix compilation warning in function 'get_cred'

[David Howells]

Hannes Eder <hannes@hanneseder.net> wrote:

> What do you suggest, report this as a gcc bug?

You could do.  It might be worth checking to see if it's fixed with a newer
gcc first, though.

David

Re: [PATCH] CRED: fix compilation warning in function 'get_cred'

[Hannes Eder]

On Fri, Nov 21, 2008 at 5:25 PM, David Howells <dhowells@redhat.com> wrote:
> Hannes Eder <hannes@hanneseder.net> wrote:
>
>> What do you suggest, report this as a gcc bug?
>
> You could do.  It might be worth checking to see if it's fixed with a newer
> gcc first, though.

The spurious warning is gone with gcc (Ubuntu 4.3.2-1ubuntu11) 4.3.2.

Hannes

Re: [PATCH] CRED: fix compilation warning in function 'get_cred'

[Hannes Eder]

On Fri, Nov 21, 2008 at 5:25 PM, David Howells <dhowells@redhat.com> wrote:
> Hannes Eder <hannes@hanneseder.net> wrote:
>
>> What do you suggest, report this as a gcc bug?
>
> You could do.  It might be worth checking to see if it's fixed with a newer
> gcc first, though.

The spurious warning is gone with gcc (Ubuntu 4.3.2-1ubuntu11) 4.3.2.

Hannes

Re: [PATCH] CRED: fix compilation warning in function 'get_cred'

[David Howells]

Hannes Eder <hannes@hanneseder.net> wrote:

> The spurious warning is gone with gcc (Ubuntu 4.3.2-1ubuntu11) 4.3.2.

Then I wouldn't worry about it too much.

David