[KPhotoAlbum] Warnings

[Johannes Zarl-Zierl]

Hi Tobias,

> I also wanted to ask this: The KPA wiki says that the KPA build process is
> "warning free zone". Actually, we currently have two warnings:
> 
> 
> One appears during cmake (I don't know since when, it's new ...):
> 
> CMake Warning (dev) at /usr/lib64/automoc4/Automoc4Config.cmake:179
> (get_directory_property):
>   Policy CMP0059 is not set: Do no treat DEFINITIONS as a built-in directory
> property.  Run "cmake --help-policy CMP0059" for policy details.  Use the
> cmake_policy command to set the policy and suppress this warning. Call
> Stack (most recent call first):
>   /usr/lib64/automoc4/Automoc4Config.cmake:243 (_add_automoc4_target)
>   /usr/share/apps/cmake/modules/KDE4Macros.cmake:1003
> (_automoc4_kde4_pre_target_handling)
>   CMakeLists.txt:451 (kde4_add_executable)
> This warning is for project developers.  Use -Wno-dev to suppress it.

I don't see this warning on my own system. I think this is a bug within 
KDE4Macros.cmake.


> /home/tobias/tmp/1/kphotoalbum-4.7/RemoteControl/RemoteCommand.cpp: In
> function 'QDataStream& operator>>(QDataStream&, RemoteControl::Category&)':
> /home/tobias/tmp/1/kphotoalbum-4.7/RemoteControl/RemoteCommand.cpp:125:68:
> warning: dereferencing type-punned pointer will break strict-aliasing rules
> [- Wstrict-aliasing]
>      stream >> category.name >> category.enabled >> (int&)
> category.viewType; ^

I had hoped that somebody else would do it (and in this one case I think that 
the warning will not lead to an actual bug). Your prodding, however has pushed 
me over the edge to go and investigate it further...

What happens here?
Somewhere else, category.viewType (which is an enum) is written to a stream as 
int. The code here is the reverser step, where the int is converted back into 
an enum value.
The conversion back into an int is a potential problem, because the enum is of 
different size than an int, and we tell the code to potentially write an int 
value into a location that does not have space for it.

What can we do about it?
Let the stream write into a temporary int, and cast the temporary value to the 
enum. This means that the compiler can at least make sure that the value that 
is written into the enum "fits".

    int tmp;
    stream >> category.name >> category.enabled >> tmp;
    category.viewType = static_cast<RemoteControl::CategoryViewType>(tmp);

I'm committing this fix in a minute or so...

Cheers,
  Johannes