libatomic-ops-dev 7.6.10-1ubuntu2 (amd64 binary) in ubuntu focal

 Libatomic-ops implements a large collection of operations, each one
 of which is a combination of an (optional) atomic memory operation,
 and a memory barrier. It also implements associated feature-test
 macros that determine whether a particular operation is available
 on the current target hardware (either directly or by synthesis).
 Libatomic-ops attempts to replace various existing files with similar
 goals, since they usually do not handle differences in memory barrier
 styles with sufficient generality.
 .
 This package provides the header files and documentation needed by
 developers.