C/C++ libraries and preprocessing

Question

I’ve always wondered the syntax of #include and of #define, as they differ greatly from the syntax of the rest of the language. I found that this is because these commands are intended for the preprocessor and not the build process "itself".

I also found that compiler manuals like Manual of the GCC discourage the use of the preprocessor, suggesting that the programmer give preference to the mechanisms of the language itself. Example: in section on command #pragma, modifying the parameters for compilation, it is recommended whenever possible to replace it with function attributes.

However, although the arguments for preference for the compiler seem coherent to me, I have never found a way to use libraries in C/C++ without the pre-processing command #include. In addition, in order to avoid the inclusion of duplicate headers, it is necessary to use include Guards or the command #pragma once, both dependent on the preprocessor.

Because C/C++ languages do not support the inclusion of libraries using compiler commands only?

In Pascal and Object Pascal we have the uses, in C# usingand in Java the import, among other examples. I know that the C/C++ languages are in constant development and updating until today, so why has this type of feature never been added?

I understand the use of the preprocessor for conditional compilation, especially in the development of compatible functions among several Sos. But wouldn’t using libraries be a very basic function to be in charge of the preprocessor? What is the justification for this?

Since I studied the subject, I feel that whenever I use libraries in C/C++ I am doing a "gambiarra".

Answer 1

Without the #include really gets very complicated, even if possible. I do not know if they say not to use even this, I imagine they speak of other things.

Because C/C++ languages do not support the inclusion of libraries using compiler commands only?

Because C was created almost 50 years ago and it wasn’t that simple, they didn’t think it through. C++ needed to maintain compatibility.

In Pascal and Object Pascal we have the uses

At first I had none of that.

C changes little, the idea is to keep it stable. C++ will have something like this soon, but I don’t know if it will totally eliminate the use of PP.

I understand the use of the preprocessor for conditional compilation

In C++ you could already in large part, and then you can in 100% cases you don’t need it.

using libraries would not be a very basic function to be in charge of the preprocessor? What is the justification for this?

It is nothing trivial to insert into the language, it is trivial in C because it is not part of the language, and therefore does not give many guarantees, if you do wrong, Abau.