c++ - Why is volatile deprecated in C++20?

Question

According to cppreference, most uses of the volatile keyword are to be deprecated in C++20. What is the disadvantage of volatile? And what is the alternative solution when not using volatile?

Answer 1

There's a good talk by the C++ committee language evolution chair on why.

Brief summary, many of the places that volatile is being removed from didn't have any understandable meaning and just caused confusion.

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Some examples from the talk:

• Volatile bit Fields should be specified by your hardware manual and/or compiler.
• Is += a single/atomic instruction? How about ++?
• How many reads/writes are needed for compare_exchange? What if it fails?
• What does void foo(int volatile n) mean? or int volatile foo()
• Should *vp; do a load? (This has changed twice in the standard.)