Using precompiled headers in msvc when building from the command line with the cl compiler

Question

Edit: I know how to use it in VS, and CMake, I am trying to find out how to do it using cl.exe on the command line and not from inside the Visual Studio IDE or using a build generator like CMake.

Original question: I am trying to use precompiled headers on windows with MSVC. mainly to bundle all Microsoft's headers in one place and precompile them for faster compile builds.

The problem is I can not figure out how to actually use pch files. I was trying following the two links from the official documentation: Create Precompiled Headers and also this: Use Precompiled Headers

I am generating the .pch file are follows:

cl /c /Ycheaders.h main.cpp

inside headers.h I do the following:

#include <windows.h>
#include <iostream>
//--- other includes that will never change ----//

And following the documentation this is how I try to use it.

cl /Yuheaders.h main.cpp

this get me the following error: fatal error C1854: cannot overwrite information formed during creation of the precompiled header in object main.obj

I assumed the documentation is wrong (because the provided command in the docs: cl /Ycheader.h main.cpp is wrong and does not work and it needs /c before it as in the comment in the example code), It did not make sense to me to compile your main.cpp so I repeated the steps above with creating the precompiled headers files with headers.cpp instead of main.cpp where headers.cpp is just an empty source file with a single include headers.h and the I get a linking error 1 unresolved external LINK error 1120 without specifying what was unresolved.

Ideally if anyone has a minimal example of how to create header files for msvc and then shows how to use them.

Answer 1

Create pch:

cl /EHsc /c /Ycheader.h header.cpp

Use pch:

cl /EHsc /Yuheader.h /Fpheader.pch main.cpp /link header.obj

Answer 2

Assuming you already have a project without precompiled headers.

Start by adding two new files: precomp.h and precomp.cpp:

precomp.cpp is simply this:

#include precomp.h

precomp.h is the header file with all the stuff you want precompiled - typically system and CRT header files:

#ifndef MY_PRECOMP_H
#define MY_PRECOMP_H

#include <windows.h>
#include <vector>
#include <map>
// etc...

#endif

Update every non-header source files (that is, the .cpp source files) files in the project to have #include "precomp.h" as the first line before any other code.

 

Now, right click on the project title in the solution explorer:

And select "Properties" to bring up the project settings for the entire project:

Under C/C++ section of the project properties. Select "precompiled headers". Then enable the Precompiled Header option to be Use (/Yu). Set the Precompiled Header File option to precomp.h. Then click OK.

Final step. Right click directly on precomp.cpp in your Solution Explorer and select "Properties".

This will display up a dialog similar to one you just saw for the project settings, but specific to this source file.

For this file's precompiled header options, select Create (/Yc) and the Precompiled Header option and precomp.h as the Header file option.

Now do a "clean" build followed by a full build. Precomp.cpp will get compiled first and generate the needed .pch file. All the other source files upon getting compiled will pull in the precompiled header file.

Answer 3

The solutions posted by Elijay and Minxin both work, however, in my case (and I am not entirely sure why) I had to reinstall the VS completely, and disabling the antivirus (I was getting strange threat warnings during compilation/running programs)

After that both of their solutions seems to produce a precompiled header that works