[SOLVED] What is __EXPORTED_HEADERS__ macro from Linux kernel used for?

Issue

I have come across the following in existing macro in application makefile: __EXPORTED_HEADERS__ added to the cflags for gcc: CPPFLAGS+=-D__EXPORTED_HEADERS__ .

I did not find the macro itself used in the code.

I see it is used in the Linux kernel, though I dont exactly understand how it is used there.

What is it used for, and why would someone compile their code with this macro defined?

Thanks.

Solution

elixir saerch __EXPORTED_HEADERS__ -> https://elixir.bootlin.com/linux/latest/source/include/uapi/linux/types.h#L9

There are kernel headers meant to be used from user space. And there are a lot of kernel headers meant to be used only inside the kernel.

What is it used for,

The __EXPORTED_HEADERS__ is used to protect against user-space source files including kernel headers not meant for user-space. In case that happens, a warning is displayed.

why would someone compile their code with this macro defined?

To silence the warning meant for user-space when compiling as kernel.

Answered By - KamilCuk

Answer Checked By - David Goodson (WPSolving Volunteer)