Atari's mintelf platform has ELF support but its libc does not provide
__cxa_atexit / __cxa_finalize, so -fuse-cxa-atexit cannot be used out of
the box. Add a minimal shim (plus a __dso_handle definition for the main
executable) so plugins can register and finalize their function-local
static destructors per DSO on unload.
Note: earlier version ran __cxa_finalize from the host via
findSymbol("__dso_handle"). That works as long as exactly one
__dso_handle ends up in the plugin's symtab (the plugin's own).
When the main binary also defines __dso_handle (so the host's
function-local statics can link with -fuse-cxa-atexit), it breaks: the
plugin link uses --just-symbols=<main binary> and imports that as a
second __dso_handle, and findSymbol can then return the host-imported
one instead of the plugin's own. The two addresses differ, so
__cxa_finalize matches nothing.
The plugin-side helper avoids the ambiguity on every target by using
whichever __dso_handle the plugin's own code already resolved against --
the same one embedded in its __cxa_atexit calls. (PSP2's plugin runtime
has always called __cxa_finalize from inside the plugin for the same
reason; see backends/plugins/psp2/plugin.cpp.)
Some toolchains (RiscOS) may not export it in certain conditions.
This list does not enforce the symbol to be here so it shouldn't fail
build on platforms without this symbol.
The ELF loader does not have access to the symbols of the main
executable, it just relocates symbols to it via fixed offsets. We need
to make sure that loaded plugins are from the same link process to
prevent crashes. An embedded build date is used for that.
svn-id: r52730
Miro Kropacek
Le Philousophe
Andre Heider