I'm doing some X11 ctypes coding, I don't know C but need some help understanding this.
In the C code below (might be C++ im not sure) we see (~0L) what does that mean? In Javascript and Python ~0 means -1.
812 int result = GetProperty(window, property_name,
813 (~0L), // (all of them)
814 &type, &format, &num_items, &properties);
Thanks
Answer
0L is a long integer value with all the bits set to zero - that's generally the definition of 0. The ~ means to invert all the bits, which leaves you with a long integer with all the bits set to one.
In two's complement arithmetic (which is almost universal) a signed value with all bits set to one is -1.
The reason for using ~0L instead of -1L is to be clearer about the intent - it's not meant to be used as a number at all, but rather as a collection of bits.