static assert if a header is included in another header but not a cpp

Static assertions in C++ are used to check conditions at compile-time. If a certain condition is not met, the compilation will fail with a specific error message. However, static assertions are typically used to check conditions related to types, constants, or template parameters, rather than checking if a header is included in another header.

To achieve what you're asking (checking if a header is included in another header but not a cpp), you can use a combination of preprocessor macros and static assertions. Here's an example of how you could do it:

1. In the header file (header_to_check.h), define a preprocessor macro that indicates the header is being included:

cppCopy code
// header_to_check.h

#pragma once



#define HEADER_INCLUDED

1. In the source file (source_to_check.cpp), include the header and define a static assertion if the preprocessor macro is not defined:

cppCopy code
// source_to_check.cpp

#include "header_to_check.h"



#ifndef HEADER_INCLUDED

static_assert(false, "header_to_check.h should be included in this source file.");

#endif



// Rest of the code for source_to_check.cpp

Now, if you include header_to_check.h in a header file but not in a .cpp source file, the static assertion in source_to_check.cpp will trigger a compile-time error. This will help ensure that the header is included in both header and source files.

Please note that this approach relies on the preprocessor and will not catch cases where the header is included using conditional compilation. Additionally, you might want to consider alternatives like using a common header that includes the target header and then including the common header in both header and source files.