On Sat, Jan 16, 2021 at 04:13:22PM +0000, Alexander Lobakin wrote:
> container_of() macro hides a local variable '__mptr' inside. This
> becomes a problem when several container_of() are nested in each
> other within single line or plain macros.
> As C preprocessor doesn't support generating random variable names,
> the sole solution is to avoid defining macros that consist only of
> container_of() calls, or they will self-shadow '__mptr' each time:
>
> In file included from ./include/linux/bitmap.h:10,
> from drivers/net/phy/phy_device.c:12:
> drivers/net/phy/phy_device.c: In function ‘phy_device_release’:
> ./include/linux/kernel.h:693:8: warning: declaration of ‘__mptr’ shadows a
> previous local [-Wshadow]
> 693 | void *__mptr = (void *)(ptr); \
> | ^~~~~~
> ./include/linux/phy.h:647:26: note: in expansion of macro ‘container_of’
> 647 | #define to_phy_device(d) container_of(to_mdio_device(d), \
> | ^~~~~~~~~~~~
> ./include/linux/mdio.h:52:27: note: in expansion of macro ‘container_of’
> 52 | #define to_mdio_device(d) container_of(d, struct mdio_device, dev)
> | ^~~~~~~~~~~~
> ./include/linux/phy.h:647:39: note: in expansion of macro ‘to_mdio_device’
> 647 | #define to_phy_device(d) container_of(to_mdio_device(d), \
> | ^~~~~~~~~~~~~~
> drivers/net/phy/phy_device.c:217:8: note: in expansion of macro
> ‘to_phy_device’
> 217 | kfree(to_phy_device(dev));
> | ^~~~~~~~~~~~~
> ./include/linux/kernel.h:693:8: note: shadowed declaration is here
> 693 | void *__mptr = (void *)(ptr); \
> | ^~~~~~
> ./include/linux/phy.h:647:26: note: in expansion of macro ‘container_of’
> 647 | #define to_phy_device(d) container_of(to_mdio_device(d), \
> | ^~~~~~~~~~~~
> drivers/net/phy/phy_device.c:217:8: note: in expansion of macro
> ‘to_phy_device’
> 217 | kfree(to_phy_device(dev));
> | ^~~~~~~~~~~~~
>
> As they are declared in header files, these warnings are highly
> repetitive and very annoying (along with the one from linux/pci.h).
>
> Convert the related macros from linux/{mdio,phy}.h to static inlines
> to avoid self-shadowing and potentially improve bug-catching.
> No functional changes implied.
>
> Signed-off-by: Alexander Lobakin <aloba...@pm.me>
Reviewed-by: Andrew Lunn <and...@lunn.ch>
Andrew
