Can I use #include "pch.h" instead of #include "stdafx.h" as my precompile header in Visual Studio C++?

17
votes

This is my first time working with C++ and properly getting into coding. I'm following the C++ tutorials on learncpp.com and I'm using Visual Studio 2017...

In the tutorial they start off with some simple "Hello, world!" code and at top of the code they put #include "stdafx.h" along with #include <iostream>. When I replicate this code myself and try to build it, I get the error:

C1010: unexpected end of file while looking for precompiled header. Did you forget to add #include "pch.h" to your source?

When looking at my solution explorer I noticed that in their tutorial in the header and source files tab they have files called "stdafx.h" and "stdafx.cpp", but for me those files are called "pch.h" and "pch.cpp".

So I then tried renaming the #include "stdafx.h" to #include "pch.h" and the code was built and executed perfectly. So should I just stick with #include "pch.h" for the rest of my code or is this some kind of issue?

Thanks!

3
c++visual-studiocompiler-errors
Make an empty project, and disregard stdafx.h. Precompiled headers are not needed. – HSK
Precompiled header name is specified in Project properties -> C / C++ -> Precompiled header tab. It can be set on per translation unit basis. – user7860670
Precompiled headers are just an additional complexity and source of errors. They aren't useful except on large projects to speed up compilation times. You should turn them off. But to answer your question you can use any name you like as long as you specify that name in your project settings. – john
@john • my project is very, very large. Turning off precompiled headers sped up compilation times about 10% faster. Without measuring how much speed up (or slow down!) precompiled headers are providing, its hard to assess the benefit. And I wholeheartedly agree with you regarding the additional complexity and source of errors. – Eljay
So many answering comments and yet this question has no answer. – Khouri Giordano

3 Answers

24
votes

The default precompiled headers name was stdafx.h for several years now. Lately, with VS 2017, they changed the default name the project wizard creates to pch.h. I don't know why but they did it.

You can adjust the name of the precompiled header file in the Project Properties under Configuration Properties -> C/C++ -> Precompiled Headers. You can also enable or disable the use of them there. You can even define this on a per file basis. You can even configure multiple different Precompiled Header files in one project.

So for you concrete question: There won't be any kind of issue replacing stdafx.h with pch.h in your tutorial. The tutorial is probably just older and hasn't been updated yet.

4
votes

Try moving "#include pch.h" to the very top of the file (before any other headers).

Some compilers won't compile content before the pre-compiled header file(s) by default. This setting can be changed though.

3
votes

In the learncpp.com tutorials, the instructor(s) recommend(s) us to turn off the "Precompiled Header" additional option when creating a new C++ project using the Windows Desktop Wizard option on Visual Studio. And it is a good idea to do so while we haven't been introduced to Header files.

However, pch.h seems to be the "new" stdafx.h, so it is not that you can use the former instead of the latter, but that you have to, at least if choosing the option of "Precompiled Header".