This change adds common C, C++, and POSIX functions to the clang-tidy unused return value checker.
We ran our commercial static analysis tool, CodeSonar, over the source code of more than 6000 projects from Fedora's package manager. During this run, we gathered information about the return value usages of various library functions. To create a list of library functions that should always have their return value checked, we required at least 20 projects to have used the library function and for over 95% of those uses to have checked the return value. Finally, we limited the list of functions to those from the C standard library, the C++ standard library, and the POSIX specification, as these are the most likely to be of interest to clang-tidy users.
No test cases have been added as there is already a test that ensures functions on this list trigger correctly and a second test that ensures the functions on this list do not trigger if a custom list is specified.