Failure to export __cxa_atexit can lead to an attempt to import a definition
from the process itself (if __cxa_atexit is referenced from another JITDylib),
but the process definition will clash with the existing non-exported definition
to produce an unexpected DuplicateDefinitionError.
This patch fixes the immediate issue by exporting __cxa_atexit. It also fixes a
bug where atexit functions in other JITDylibs were not being run by adding a
copy of run_atexits_helper to every JITDylib.
A follow up patch will deal with the bug where definition generators are called
despite a non-exported definition being present.
minimal.ll contains a main function that returns zero, and
single-function-call.ll contains a main function that calls a foo function that
returns zero. These minimal tests can help to rule out some trivial JIT bugs
when other tests fail.
This commit also renames hello.ll to global-ctors-and-dtors.ll, which better
reflects what it is actually testing.
llvm-svn: 344863