[PATCH] Staging: dgnc: fixed code style issue

[PATCH] Staging: dgnc: fixed code style issue

[Yorick Rommers]

A patch for a line being too long (>80) in dgnc_mgmt.c,
fixed by making a temporary value for dgnc_Board[brd], and removing
an unnecessary typecast.

Signed-off-by: Yorick Rommers <yorick-rommers@hotmail.com>
---
 drivers/staging/dgnc/dgnc_mgmt.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/dgnc/dgnc_mgmt.c b/drivers/staging/dgnc/dgnc_mgmt.c
index b13318a..0e75d37 100644
--- a/drivers/staging/dgnc/dgnc_mgmt.c
+++ b/drivers/staging/dgnc/dgnc_mgmt.c
@@ -143,12 +143,14 @@ long dgnc_mgmt_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 		di.info_bdnum = brd;
 
 		spin_lock_irqsave(&dgnc_Board[brd]->bd_lock, flags);
+		struct dgnc_board *bd = dgnc_Board[brd];
 
 		di.info_bdtype = dgnc_Board[brd]->dpatype;
 		di.info_bdstate = dgnc_Board[brd]->dpastatus;
 		di.info_ioport = 0;
 		di.info_physaddr = (ulong) dgnc_Board[brd]->membase;
-		di.info_physsize = (ulong) dgnc_Board[brd]->membase - dgnc_Board[brd]->membase_end;
+		di.info_physsize = bd->membase - bd->membase_end;
+
 		if (dgnc_Board[brd]->state != BOARD_FAILED)
 			di.info_nports = dgnc_Board[brd]->nasync;
 		else
-- 
2.3.5

Re: [PATCH] Staging: dgnc: fixed code style issue

[Joe Perches]

On Sun, 2015-04-19 at 21:18 +0200, Yorick Rommers wrote:
> A patch for a line being too long (>80) in dgnc_mgmt.c,
> fixed by making a temporary value for dgnc_Board[brd], and removing
> an unnecessary typecast.

Hello Yorick.

The patch subject isn't very descriptive.

A better subject might be something like:
"staging: dgnc: Use a temporary for repeated dereferences"

> diff --git a/drivers/staging/dgnc/dgnc_mgmt.c b/drivers/staging/dgnc/dgnc_mgmt.c
[]
> @@ -143,12 +143,14 @@ long dgnc_mgmt_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
>  		di.info_bdnum = brd;
>  
>  		spin_lock_irqsave(&dgnc_Board[brd]->bd_lock, flags);
> +		struct dgnc_board *bd = dgnc_Board[brd];

Linux style doesn't declare variables in the middle
of a function,  Variables are only declared after
an open brace.

>  
>  		di.info_bdtype = dgnc_Board[brd]->dpatype;
>  		di.info_bdstate = dgnc_Board[brd]->dpastatus;

Please change all the references of dgnc_Board[brd]-> to bd->
in this function instead of just the long line ones.

>  		di.info_ioport = 0;
>  		di.info_physaddr = (ulong) dgnc_Board[brd]->membase;
> -		di.info_physsize = (ulong) dgnc_Board[brd]->membase - dgnc_Board[brd]->membase_end;
> +		di.info_physsize = bd->membase - bd->membase_end;
> +
>  		if (dgnc_Board[brd]->state != BOARD_FAILED)
>  			di.info_nports = dgnc_Board[brd]->nasync;
>  		else


Something like:

 drivers/staging/dgnc/dgnc_mgmt.c | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/drivers/staging/dgnc/dgnc_mgmt.c b/drivers/staging/dgnc/dgnc_mgmt.c
index b13318a..215f37b 100644
--- a/drivers/staging/dgnc/dgnc_mgmt.c
+++ b/drivers/staging/dgnc/dgnc_mgmt.c
@@ -129,8 +129,8 @@ long dgnc_mgmt_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 	case DIGI_GETBD:
 	{
 		int brd;
-
 		struct digi_info di;
+		struct dgnc_board *bd;
 
 		if (copy_from_user(&brd, uarg, sizeof(int)))
 			return -EFAULT;
@@ -142,19 +142,21 @@ long dgnc_mgmt_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 
 		di.info_bdnum = brd;
 
-		spin_lock_irqsave(&dgnc_Board[brd]->bd_lock, flags);
+		bd = dgnc_Board[brd];
+
+		spin_lock_irqsave(&bd->bd_lock, flags);
 
-		di.info_bdtype = dgnc_Board[brd]->dpatype;
-		di.info_bdstate = dgnc_Board[brd]->dpastatus;
+		di.info_bdtype = bd->dpatype;
+		di.info_bdstate = bd->dpastatus;
 		di.info_ioport = 0;
-		di.info_physaddr = (ulong) dgnc_Board[brd]->membase;
-		di.info_physsize = (ulong) dgnc_Board[brd]->membase - dgnc_Board[brd]->membase_end;
-		if (dgnc_Board[brd]->state != BOARD_FAILED)
-			di.info_nports = dgnc_Board[brd]->nasync;
+		di.info_physaddr = bd->membase;
+		di.info_physsize = bd->membase - bd->membase_end;
+		if (bd->state != BOARD_FAILED)
+			di.info_nports = bd->nasync;
 		else
 			di.info_nports = 0;
 
-		spin_unlock_irqrestore(&dgnc_Board[brd]->bd_lock, flags);
+		spin_unlock_irqrestore(&bd->bd_lock, flags);
 
 		if (copy_to_user(uarg, &di, sizeof(di)))
 			return -EFAULT;

[PATCH] Staging: dgnc: Using temporary value for repeated dereferences.

[Yorick Rommers]

Hello Joe,

Thank you once again for the feedback.
I've changed my patch accordingly, see below.

--------------------------------------

A patch for a line being too long (>80) in dgnc_mgmt.c,
fixed by making a temporary value for dgnc_Board[brd],
replacing all instanced of dgnc_Board[brd] with temporary value,
and removing unnecessary typecasts.

Signed-off-by: Yorick Rommers <yorick-rommers@hotmail.com>
---
 drivers/staging/dgnc/dgnc_mgmt.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/drivers/staging/dgnc/dgnc_mgmt.c b/drivers/staging/dgnc/dgnc_mgmt.c
index b13318a..0437117 100644
--- a/drivers/staging/dgnc/dgnc_mgmt.c
+++ b/drivers/staging/dgnc/dgnc_mgmt.c
@@ -131,6 +131,7 @@ long dgnc_mgmt_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 		int brd;

 		struct digi_info di;
+		struct dgnc_board *bd = dgnc_Board[brd];

 		if (copy_from_user(&brd, uarg, sizeof(int)))
 			return -EFAULT;
@@ -142,19 +143,19 @@ long dgnc_mgmt_ioctl(struct file *file, unsigned int cmd, unsigned long arg)

 		di.info_bdnum = brd;

-		spin_lock_irqsave(&dgnc_Board[brd]->bd_lock, flags);
+		spin_lock_irqsave(&bd->bd_lock, flags);

-		di.info_bdtype = dgnc_Board[brd]->dpatype;
-		di.info_bdstate = dgnc_Board[brd]->dpastatus;
+		di.info_bdtype = bd->dpatype;
+		di.info_bdstate = bd->dpastatus;
 		di.info_ioport = 0;
-		di.info_physaddr = (ulong) dgnc_Board[brd]->membase;
-		di.info_physsize = (ulong) dgnc_Board[brd]->membase - dgnc_Board[brd]->membase_end;
-		if (dgnc_Board[brd]->state != BOARD_FAILED)
-			di.info_nports = dgnc_Board[brd]->nasync;
+		di.info_physaddr = bd->membase;
+		di.info_physsize = bd->membase - bd->membase_end;
+		if (bd->state != BOARD_FAILED)
+			di.info_nports = bd->nasync;
 		else
 			di.info_nports = 0;

-		spin_unlock_irqrestore(&dgnc_Board[brd]->bd_lock, flags);
+		spin_unlock_irqrestore(&bd->bd_lock, flags);

 		if (copy_to_user(uarg, &di, sizeof(di)))
 			return -EFAULT;
--
2.3.5

Re: [PATCH] Staging: dgnc: Using temporary value for repeated dereferences.

[Joe Perches]

On Sun, 2015-04-19 at 23:58 +0200, Yorick Rommers wrote:
> Hello Joe,
> 
> Thank you once again for the feedback.
> I've changed my patch accordingly, see below.
> 
> --------------------------------------
> 
> A patch for a line being too long (>80) in dgnc_mgmt.c,
> fixed by making a temporary value for dgnc_Board[brd],
> replacing all instanced of dgnc_Board[brd] with temporary value,
> and removing unnecessary typecasts.
> 
> Signed-off-by: Yorick Rommers <yorick-rommers@hotmail.com>
> ---
>  drivers/staging/dgnc/dgnc_mgmt.c | 17 +++++++++--------
>  1 file changed, 9 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/staging/dgnc/dgnc_mgmt.c b/drivers/staging/dgnc/dgnc_mgmt.c
> index b13318a..0437117 100644
> --- a/drivers/staging/dgnc/dgnc_mgmt.c
> +++ b/drivers/staging/dgnc/dgnc_mgmt.c
> @@ -131,6 +131,7 @@ long dgnc_mgmt_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
>  		int brd;
> 
>  		struct digi_info di;
> +		struct dgnc_board *bd = dgnc_Board[brd];

Please read the code.
brd is got from userspace and you've dereferenced
it before getting the value from userspace.

>  		if (copy_from_user(&brd, uarg, sizeof(int)))
>  			return -EFAULT;

Look again at the code I suggested.

Re: [PATCH] Staging: dgnc: Using temporary value for repeated dereferences.

[Joe Perches]

On Sun, 2015-04-19 at 23:58 +0200, Yorick Rommers wrote:
> Hello Joe,
> 
> Thank you once again for the feedback.
> I've changed my patch accordingly, see below.
> 
> --------------------------------------
> 
> A patch for a line being too long (>80) in dgnc_mgmt.c,
> fixed by making a temporary value for dgnc_Board[brd],
> replacing all instanced of dgnc_Board[brd] with temporary value,
> and removing unnecessary typecasts.
> 
> Signed-off-by: Yorick Rommers <yorick-rommers@hotmail.com>
> ---
>  drivers/staging/dgnc/dgnc_mgmt.c | 17 +++++++++--------
>  1 file changed, 9 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/staging/dgnc/dgnc_mgmt.c b/drivers/staging/dgnc/dgnc_mgmt.c
> index b13318a..0437117 100644
> --- a/drivers/staging/dgnc/dgnc_mgmt.c
> +++ b/drivers/staging/dgnc/dgnc_mgmt.c
> @@ -131,6 +131,7 @@ long dgnc_mgmt_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
>  		int brd;
> 
>  		struct digi_info di;
> +		struct dgnc_board *bd = dgnc_Board[brd];

Please read the code.
brd is got from userspace and you've dereferenced
it before getting the value from userspace.

>  		if (copy_from_user(&brd, uarg, sizeof(int)))
>  			return -EFAULT;

Look again at the code I suggested.


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[PATCH] Staging: dgnc: Using a temporary value for repeated dereferences.

[Yorick Rommers]

Sorry, it has been changed in the patch below.

---------------------------------------

A patch for a line being too long (>80) in dgnc_mgmt.c,
fixed by making a temporary value for dgnc_Board[brd],
replacing all instanced of dgnc_Board[brd] with temporary value,
and removing unnecessary typecasts.

Signed-off-by: Yorick Rommers <yorick-rommers@hotmail.com>
---
 drivers/staging/dgnc/dgnc_mgmt.c | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/drivers/staging/dgnc/dgnc_mgmt.c b/drivers/staging/dgnc/dgnc_mgmt.c
index b13318a..ac2581a 100644
--- a/drivers/staging/dgnc/dgnc_mgmt.c
+++ b/drivers/staging/dgnc/dgnc_mgmt.c
@@ -131,6 +131,7 @@ long dgnc_mgmt_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 		int brd;

 		struct digi_info di;
+		struct dgnc_board *bd;

 		if (copy_from_user(&brd, uarg, sizeof(int)))
 			return -EFAULT;
@@ -142,19 +143,21 @@ long dgnc_mgmt_ioctl(struct file *file, unsigned int cmd, unsigned long arg)

 		di.info_bdnum = brd;

-		spin_lock_irqsave(&dgnc_Board[brd]->bd_lock, flags);
+		bd = dgnc_Board[brd];

-		di.info_bdtype = dgnc_Board[brd]->dpatype;
-		di.info_bdstate = dgnc_Board[brd]->dpastatus;
+		spin_lock_irqsave(&bd->bd_lock, flags);
+
+		di.info_bdtype = bd->dpatype;
+		di.info_bdstate = bd->dpastatus;
 		di.info_ioport = 0;
-		di.info_physaddr = (ulong) dgnc_Board[brd]->membase;
-		di.info_physsize = (ulong) dgnc_Board[brd]->membase - dgnc_Board[brd]->membase_end;
-		if (dgnc_Board[brd]->state != BOARD_FAILED)
-			di.info_nports = dgnc_Board[brd]->nasync;
+		di.info_physaddr = bd->membase;
+		di.info_physsize = bd->membase - bd->membase_end;
+		if (bd->state != BOARD_FAILED)
+			di.info_nports = bd->nasync;
 		else
 			di.info_nports = 0;

-		spin_unlock_irqrestore(&dgnc_Board[brd]->bd_lock, flags);
+		spin_unlock_irqrestore(&bd->bd_lock, flags);

 		if (copy_to_user(uarg, &di, sizeof(di)))
 			return -EFAULT;
--
2.3.5

[PATCH] Staging: dgnc: Using a temporary value for repeated dereferences.

[Yorick Rommers]

Sorry, it has been changed in the patch below.

---------------------------------------

A patch for a line being too long (>80) in dgnc_mgmt.c,
fixed by making a temporary value for dgnc_Board[brd],
replacing all instanced of dgnc_Board[brd] with temporary value,
and removing unnecessary typecasts.

Signed-off-by: Yorick Rommers <yorick-rommers@hotmail.com>
---
 drivers/staging/dgnc/dgnc_mgmt.c | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/drivers/staging/dgnc/dgnc_mgmt.c b/drivers/staging/dgnc/dgnc_mgmt.c
index b13318a..ac2581a 100644
--- a/drivers/staging/dgnc/dgnc_mgmt.c
+++ b/drivers/staging/dgnc/dgnc_mgmt.c
@@ -131,6 +131,7 @@ long dgnc_mgmt_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 		int brd;

 		struct digi_info di;
+		struct dgnc_board *bd;

 		if (copy_from_user(&brd, uarg, sizeof(int)))
 			return -EFAULT;
@@ -142,19 +143,21 @@ long dgnc_mgmt_ioctl(struct file *file, unsigned int cmd, unsigned long arg)

 		di.info_bdnum = brd;

-		spin_lock_irqsave(&dgnc_Board[brd]->bd_lock, flags);
+		bd = dgnc_Board[brd];

-		di.info_bdtype = dgnc_Board[brd]->dpatype;
-		di.info_bdstate = dgnc_Board[brd]->dpastatus;
+		spin_lock_irqsave(&bd->bd_lock, flags);
+
+		di.info_bdtype = bd->dpatype;
+		di.info_bdstate = bd->dpastatus;
 		di.info_ioport = 0;
-		di.info_physaddr = (ulong) dgnc_Board[brd]->membase;
-		di.info_physsize = (ulong) dgnc_Board[brd]->membase - dgnc_Board[brd]->membase_end;
-		if (dgnc_Board[brd]->state != BOARD_FAILED)
-			di.info_nports = dgnc_Board[brd]->nasync;
+		di.info_physaddr = bd->membase;
+		di.info_physsize = bd->membase - bd->membase_end;
+		if (bd->state != BOARD_FAILED)
+			di.info_nports = bd->nasync;
 		else
 			di.info_nports = 0;

-		spin_unlock_irqrestore(&dgnc_Board[brd]->bd_lock, flags);
+		spin_unlock_irqrestore(&bd->bd_lock, flags);

 		if (copy_to_user(uarg, &di, sizeof(di)))
 			return -EFAULT;
--
2.3.5

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Re: [PATCH] Staging: dgnc: fixed code style issue

[Dan Carpenter]

On Sun, Apr 19, 2015 at 09:18:23PM +0200, Yorick Rommers wrote:
> A patch for a line being too long (>80) in dgnc_mgmt.c,
> fixed by making a temporary value for dgnc_Board[brd], and removing
> an unnecessary typecast.
> 
> Signed-off-by: Yorick Rommers <yorick-rommers@hotmail.com>
> ---
>  drivers/staging/dgnc/dgnc_mgmt.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/staging/dgnc/dgnc_mgmt.c b/drivers/staging/dgnc/dgnc_mgmt.c
> index b13318a..0e75d37 100644
> --- a/drivers/staging/dgnc/dgnc_mgmt.c
> +++ b/drivers/staging/dgnc/dgnc_mgmt.c
> @@ -143,12 +143,14 @@ long dgnc_mgmt_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
>  		di.info_bdnum = brd;
>  
>  		spin_lock_irqsave(&dgnc_Board[brd]->bd_lock, flags);
> +		struct dgnc_board *bd = dgnc_Board[brd];

Change the others as well.

>  
>  		di.info_bdtype = dgnc_Board[brd]->dpatype;

		di.info_bdtype = bd->dpatype;

>  		di.info_bdstate = dgnc_Board[brd]->dpastatus;

		di.info_bdstate = bd->dpastatus;

>  		di.info_ioport = 0;
>  		di.info_physaddr = (ulong) dgnc_Board[brd]->membase;
> -		di.info_physsize = (ulong) dgnc_Board[brd]->membase - dgnc_Board[brd]->membase_end;
> +		di.info_physsize = bd->membase - bd->membase_end;
> +
>  		if (dgnc_Board[brd]->state != BOARD_FAILED)
>  			di.info_nports = dgnc_Board[brd]->nasync;
                                         ^^^^^^^^^^^^^^^
Etc.

regards,
dan carpenter

Re: [PATCH] Staging: dgnc: Using temporary value for repeated dereferences.

[Dan Carpenter]

On Sun, Apr 19, 2015 at 11:58:53PM +0200, Yorick Rommers wrote:
> Hello Joe,
> 
> Thank you once again for the feedback.
> I've changed my patch accordingly, see below.
> 
> --------------------------------------

The patch is nice except for this chunk.  And also you should be putting
version numbers in the patch description:

[PATCH v4] Staging: dgnc: Using temporary variable to save space

> 
> A patch for a line being too long (>80) in dgnc_mgmt.c,
> fixed by making a temporary value for dgnc_Board[brd],
> replacing all instanced of dgnc_Board[brd] with temporary value,
> and removing unnecessary typecasts.
> 
> Signed-off-by: Yorick Rommers <yorick-rommers@hotmail.com>
> ---

And put a note under the cut off here.

---
v4: Removed email to Joe Perches from the patch description

regards,
dan carpenter

Re: [PATCH] Staging: dgnc: Using temporary value for repeated dereferences.

[Dan Carpenter]

On Sun, Apr 19, 2015 at 05:54:19PM -0700, Joe Perches wrote:
> > diff --git a/drivers/staging/dgnc/dgnc_mgmt.c b/drivers/staging/dgnc/dgnc_mgmt.c
> > index b13318a..0437117 100644
> > --- a/drivers/staging/dgnc/dgnc_mgmt.c
> > +++ b/drivers/staging/dgnc/dgnc_mgmt.c
> > @@ -131,6 +131,7 @@ long dgnc_mgmt_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
> >  		int brd;
> > 
> >  		struct digi_info di;
> > +		struct dgnc_board *bd = dgnc_Board[brd];
> 
> Please read the code.
> brd is got from userspace and you've dereferenced
> it before getting the value from userspace.

Gar.  Oops.  I totally missed that when I looked at this patch.  :(

You would hope that GCC would warn about the uninitialized variable but
it doesn't.


regards,
dan carpenter

gcc doesn't warn about uninitialized variable use in switch/case with -O (was: Re: [PATCH] Staging: dgnc: Using temporary value for repeated dereferences)

[Joe Perches]

On Mon, 2015-04-20 at 11:33 +0300, Dan Carpenter wrote:
> You would hope that GCC would warn about the uninitialized variable but
> it doesn't.

That's odd.  So I filed this new gcc bugzilla:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65812)

gcc 4.9.1 doesn't warn about uninitialized variable use
declared in a switch/case statement when compiled with -O

Here is a small example:

$ cat t.c
struct foo {
       int bar[100];
};

void foo_1(void)
{
	unsigned int m;
	extern struct foo *array[100];
	struct foo *a = array[m];

	a = a;
}

void foo_2(void)
{
	int i = 1;

	switch (i) {
	case 1: {
		unsigned int m;
		extern struct foo *array[100];
		struct foo *a = array[m];

		a = a;
		break;
	}
	}
}

$

gcc warns properly about both foo_1 and foo_2 without -O

$ gcc -c -Wall t.c
t.c: In function ‘foo_1’:
t.c:9:14: warning: ‘m’ is used uninitialized in this function
[-Wuninitialized]
  struct foo *a = array[m];
              ^
t.c: In function ‘foo_2’:
t.c:21:15: warning: ‘m’ may be used uninitialized in this function
[-Wmaybe-uninitialized]
   struct foo *a = array[m];
               ^
$

but gcc warns about foo_1 but not foo_2 with -O

$ gcc -c -Wall -O t.c
t.c: In function ‘foo_1’:
t.c:9:14: warning: ‘m’ is used uninitialized in this function
[-Wuninitialized]
  struct foo *a = array[m];
              ^

$ gcc -v
Using built-in specs.
COLLECT_GCC=/usr/bin/gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.9/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu
4.9.1-16ubuntu6' --with-bugurl=file:///usr/share/doc/gcc-4.9/README.Bugs
--enable-languages=c,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr
--program-suffix=-4.9 --enable-shared --enable-linker-build-id
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--with-gxx-include-dir=/usr/include/c++/4.9 --libdir=/usr/lib
--enable-nls --with-sysroot=/ --enable-clocale=gnu
--enable-libstdcxx-debug --enable-libstdcxx-time=yes
--enable-gnu-unique-object --disable-vtable-verify --enable-plugin
--with-system-zlib --disable-browser-plugin --enable-java-awt=gtk
--enable-gtk-cairo
--with-java-home=/usr/lib/jvm/java-1.5.0-gcj-4.9-amd64/jre
--enable-java-home
--with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-4.9-amd64
--with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-4.9-amd64
--with-arch-directory=amd64
--with-ecj-jar=/usr/share/java/eclipse-ecj.jar --enable-objc-gc
--enable-multiarch --disable-werror --with-arch-32=i686 --with-abi=m64
--with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic
--enable-checking=release --build=x86_64-linux-gnu
--host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 4.9.1 (Ubuntu 4.9.1-16ubuntu6) 

Re: gcc doesn't warn about uninitialized variable use in switch/case with -O (was: Re: [PATCH] Staging: dgnc: Using temporary value for repeated dereferences)

[Joe Perches]

On Mon, 2015-04-20 at 03:42 -0700, Joe Perches wrote:
> On Mon, 2015-04-20 at 11:33 +0300, Dan Carpenter wrote:
> > You would hope that GCC would warn about the uninitialized variable but
> > it doesn't.
> 
> That's odd.  So I filed this new gcc bugzilla:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65812)
> 
> gcc 4.9.1 doesn't warn about uninitialized variable use
> declared in a switch/case statement when compiled with -O

Hey Dan/Yorick

A bit more investigation:

It's true that gcc doesn't report the uninitialized
variable for the code I showed, but that's probably not
the reason the "may be used uninitialized" warning is not
shown for the dgnc code as patched by Yorick.

The example code doesn't show the "uninitialized" warning
because gcc's dead code elimination is set by -O and the
sample code foo_2 function switch/case is eliminated.

Perhaps the warning is not shown for this dgnc patch
because your .config has CONFIG_GCOV_PROFILE_ALL set.

That enables the gcc -fprofile-arcs option which masks the
warning,  I don't know why.

Maybe see:

commit 2521f2c228ad750701ba4702484e31d876dbc386
Author: Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
Date:   Wed Jun 17 16:28:08 2009 -0700

    gcov: add gcov profiling infrastructure
    
    Enable the use of GCC's coverage testing tool gcov [1] with the Linux
    kernel.  gcov may be useful for:
    
     * debugging (has this code been reached at all?)
     * test improvement (how do I change my test to cover these lines?)
     * minimizing kernel configurations (do I need this option if the
       associated code is never run?)
    
    The profiling patch incorporates the following changes:
    
     * change kbuild to include profiling flags
     * provide functions needed by profiling code
     * present profiling data as files in debugfs
    
    Note that on some architectures, enabling gcc's profiling option
    "-fprofile-arcs" for the entire kernel may trigger compile/link/
    run-time problems, some of which are caused by toolchain bugs and
    others which require adjustment of architecture code.
    
    For this reason profiling the entire kernel is initially restricted
    to those architectures for which it is known to work without changes.
    This restriction can be lifted once an architecture has been tested
    and found compatible with gcc's profiling. Profiling of single files
    or directories is still available on all platforms (see config help
    text).
    
    [1] http://gcc.gnu.org/onlinedocs/gcc/Gcov.html
  

Re: gcc doesn't warn about uninitialized variable use in switch/case with -O (was: Re: [PATCH] Staging: dgnc: Using temporary value for repeated dereferences)

[Joe Perches]

On Mon, 2015-04-20 at 03:42 -0700, Joe Perches wrote:
> On Mon, 2015-04-20 at 11:33 +0300, Dan Carpenter wrote:
> > You would hope that GCC would warn about the uninitialized variable but
> > it doesn't.
> 
> That's odd.  So I filed this new gcc bugzilla:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65812)
> 
> gcc 4.9.1 doesn't warn about uninitialized variable use
> declared in a switch/case statement when compiled with -O

Hey Dan/Yorick

A bit more investigation:

It's true that gcc doesn't report the uninitialized
variable for the code I showed, but that's probably not
the reason the "may be used uninitialized" warning is not
shown for the dgnc code as patched by Yorick.

The example code doesn't show the "uninitialized" warning
because gcc's dead code elimination is set by -O and the
sample code foo_2 function switch/case is eliminated.

Perhaps the warning is not shown for this dgnc patch
because your .config has CONFIG_GCOV_PROFILE_ALL set.

That enables the gcc -fprofile-arcs option which masks the
warning,  I don't know why.

Maybe see:

commit 2521f2c228ad750701ba4702484e31d876dbc386
Author: Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
Date:   Wed Jun 17 16:28:08 2009 -0700

    gcov: add gcov profiling infrastructure
    
    Enable the use of GCC's coverage testing tool gcov [1] with the Linux
    kernel.  gcov may be useful for:
    
     * debugging (has this code been reached at all?)
     * test improvement (how do I change my test to cover these lines?)
     * minimizing kernel configurations (do I need this option if the
       associated code is never run?)
    
    The profiling patch incorporates the following changes:
    
     * change kbuild to include profiling flags
     * provide functions needed by profiling code
     * present profiling data as files in debugfs
    
    Note that on some architectures, enabling gcc's profiling option
    "-fprofile-arcs" for the entire kernel may trigger compile/link/
    run-time problems, some of which are caused by toolchain bugs and
    others which require adjustment of architecture code.
    
    For this reason profiling the entire kernel is initially restricted
    to those architectures for which it is known to work without changes.
    This restriction can be lifted once an architecture has been tested
    and found compatible with gcc's profiling. Profiling of single files
    or directories is still available on all platforms (see config help
    text).
    
    [1] http://gcc.gnu.org/onlinedocs/gcc/Gcov.html
  

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Re: [PATCH] Staging: dgnc: Using a temporary value for repeated dereferences.

[Greg KH]

On Mon, Apr 20, 2015 at 09:33:04AM +0200, Yorick Rommers wrote:
> Sorry, it has been changed in the patch below.
> 
> ---------------------------------------
> 
> A patch for a line being too long (>80) in dgnc_mgmt.c,
> fixed by making a temporary value for dgnc_Board[brd],
> replacing all instanced of dgnc_Board[brd] with temporary value,
> and removing unnecessary typecasts.
> 
> Signed-off-by: Yorick Rommers <yorick-rommers@hotmail.com>
> ---
>  drivers/staging/dgnc/dgnc_mgmt.c | 19 +++++++++++--------
>  1 file changed, 11 insertions(+), 8 deletions(-)

I can't apply this as-is, please fix up and resend in a format that I
can apply it in.

thanks,

greg k-h

Re: [PATCH] Staging: dgnc: Using a temporary value for repeated dereferences.

[Greg KH]

On Mon, Apr 20, 2015 at 09:33:04AM +0200, Yorick Rommers wrote:
> Sorry, it has been changed in the patch below.
> 
> ---------------------------------------
> 
> A patch for a line being too long (>80) in dgnc_mgmt.c,
> fixed by making a temporary value for dgnc_Board[brd],
> replacing all instanced of dgnc_Board[brd] with temporary value,
> and removing unnecessary typecasts.
> 
> Signed-off-by: Yorick Rommers <yorick-rommers@hotmail.com>
> ---
>  drivers/staging/dgnc/dgnc_mgmt.c | 19 +++++++++++--------
>  1 file changed, 11 insertions(+), 8 deletions(-)

I can't apply this as-is, please fix up and resend in a format that I
can apply it in.

thanks,

greg k-h
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