pragma directive

Saw this on Isaac ROS code at NVIDIA.

The pragma directive is a special purpose directive and is used to turn on or off some features. They are compiler-specific.

Resources

• https://www.cprogramming.com/reference/preprocessor/pragma.html
• https://www.geeksforgeeks.org/pragma-directive-in-c-c/#

They use like this

#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wpedantic"
...
#pragma GCC diagnostic pop

pragma once

So apparently you can use #pragma once instead of the #ifndef.

The thing is that ifndef is standardized, whereas pragma is compiler specific.

But this is what we do at NVIDIA at the top of every .hpp file

#pragma once

Discussion

• https://www.reddit.com/r/Cplusplus/comments/a5mu2y/old_c_vs_modern_c_pragma_once_vs_ifndef_using/
• https://beesbuzz.biz/code/1473-pragma-once-vs-ifndef-define