cprogram

Use :

While you can technically open and read files from kernel space, it's usually a bad idea for multiple reasons. Whatever information is provided under /proc is already available to the kernel, you just need to figure out where it is and how to obtain it, and you will be able to do everything in your module without reading any file.

You are interested in knowing how much RAM is a particular process using given its PID, and you are correct that this statistic is available in /proc//status: in fact, it is labeled as "VmRSS" which means "virtual memory resident set size". If we take a look at the kernel source code, we can see exactly how that number is calculated:

The kernel function called when reading /proc//status is proc_pid_status() in fs/proc/array.c, which then calls (among the other things) task_mem().

You need to specify the source.c as a source for the program.pyx file. One way to do so would be to add the header comment # distutils: sources = CSourceCode/source.c to top of your program.pyx file. You can see the Cython guild on Configuring the C Build for more information.

Besides from that you normally don't include .c files, but .h files instead, and that the following is bad practice, you can include C files into .cpp / .hpp files by wrapping the include into an extern "C":

Combining all the suggestions in the top comments:

To compute the factorial recursively, i must be a positive integer. So that either the value of i is 0 or 1 the factorial will be 1.

If not, then call the recursive factorial algorithm with (i - 1) then multiply the result by i and return that value as shown:

In C, arrays are contiguous chunks of memory, which means every element is next to each other in memory. So, a pointer to the first element combined with the knowledge of the type of the element lets you denote an array with just a pointer to the first element. Note that this does not include information on length, which is why many C functions that deal with arrays (like memcpy) also take a parameter for the length.

The constructor of virtual base is constructed. It is constructed conditionally. That is, the constructor of the most derived class calls the constructor of the virtual base. If - this is the condition - the derived class with virtual base is not the concrete class of the constructed object, then it will not construct the virtual base because it has already been constructed by the concrete class. But otherwise it will construct the virtual base.

So, you must correctly initialise the virtual base class in constructors of all derived classes. You simply must know that specific initialisation doesn't necessarily happen in case the concrete class is not the one which you are writing. The compiler doesn't and cannot know whether you will ever create direct instances of those intermediate classes, so it cannot simply ignore their broken constructors.

If you made those intermediate classes abstract, then the compiler would know that they are never the most concrete type and thus their constructor would not be required to initialise the virtual base.

You're using sizeof(string). That's the number of bytes, not the number of characters. Since you're using C++, use std::wstring::size().