+ 2

This parameter is confusing me

I'm learning opengl, and one of the parameters of the function glShaderSource() is: const GLchar* const* string The only thing I can understand from this expression is that neither the address pointed to by the pointer nor the value of the address can be changed (because there are 2 "const" expressions). But why are there 2 asterisks?

30th Nov 2020, 2:08 PM
Rajdeep Deka
Rajdeep Deka - avatar
2 odpowiedzi
+ 1
what you need to know is that glShaderSource expects two related sequences which are the C-style arrays of values. The #1 sequence is an array of C-strings, either zero-terminated or not and the #2 sequence is an array of integers, indicating the length of each of the strings in the first sequence. Note that the sequence is optional if the strings are Zero-terminated as the library will find the strings by itself. --------------------------------------------------------------------------------------------------------- Let me try to simplify by tackling it in steps: -------------------------------------------------------- #1 const GLchar is an immutable (constant) character. #2 const GLchar * is a pointer to immutable GLchars, in this case your shader source. #3 const GLchar * const is an immutable pointer to immutable GLchars, that means the pointer itself can not be changed to point somewhere else. #4 const GLchar * const * is a pointer to an immutable pointer to immutable GLchars. #5 string is the name of the parameter. I don't know if it make a little sense now. The GL-prefixed types are because the OpenGL specification needs to talk about types without tying itself into a particular language, so it introduces aliases of common C types.
1st Dec 2020, 7:40 AM
Dyondzani Clement.Masinge
Dyondzani Clement.Masinge - avatar
0
Thanks for clarifying this concept for me!
2nd Dec 2020, 6:48 AM
Rajdeep Deka
Rajdeep Deka - avatar