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Peter Wortmann authored
This tells debuggers such as GDB how to "unwind" a program state, which allows them to walk the stack up. Notes: * The code is quite general, perhaps unnecessarily so. Unless we get more unwind information, only the first case of pprSetUnwind will get used - and pprUnwindExpr and pprUndefUnwind will never be called. It just so happens that this is a point where we can get a lot of features cheaply, even if we don't use them. * When determining what location to show for a return address, most debuggers check the map for "rip-1", assuming that's where the "call" instruction is. For tables-next-to-code, that happens to always be the end of an info table. We therefore cheat a bit here by shifting .debug_frame information so it covers the end of the info table, as well as generating a .loc directive for the info table data. Debuggers will still show the wrong label for the return address, though. Haven't found a way around that one yet. (From Phabricator D396)
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