Le lundi 16 juillet 2012 23:40:01 Jason L Tibbitts III, vous avez écrit : > I ran into problems compiling the program ZoneMinder on Fedora rawhide > (currently using something around 3.5rc6) which do not appear with 3.4 > kernels. With help this was traced to commit > 6016af82eafcb6e086a8f2a2197b46029a843d68, "[media] v4l2: use __u32 > rather than enums in ioctl() structs" which changed videodev2.h in a way > which appears to be incompatible with C++. > > This results in code such as the following: > enum v4l2_buf_type type = v4l2_data.fmt.type;
That code is dangerous, probably even more so in C++. If the running kernel version is more recent than the kernel header version that userland was compiled with, the field value could be outside the range of the enumeration. > failing to compile with: > zm_local_camera.cpp:1523:49: error: invalid conversion from '__u32 > {aka unsigned int}' to 'v4l2_buf_type' [-fpermissive] > but only when compiled with the headers from a 3.5 kernel. > > I'm very far from a C++ expert. I talked with some people who do grok > it and the issue comes down to restrictions on assignments of ints to > enums > and additionally that enums in C++ don't have defined size. That cannot be true. Your C++ compiler must agree with the kernel's C compiler on the size of enum. If they did not, V4L2 would not have ever worked from C++ code in previous kernel versions. -- Rémi Denis-Courmont http://www.remlab.net/ http://fi.linkedin.com/in/remidenis -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/