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[debugging-the-compiler] Explain how one can use -R to set a breakpoint at a relative assembly offset. #30690

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[debugging-the-compiler] Explain how one can use -R to set a breakpoint at a relative assembly offset. #30690

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11 changes: 11 additions & 0 deletions docs/DebuggingTheCompiler.rst
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Expand Up @@ -359,6 +359,17 @@ we know to ignore swift_getGenericMetadata 84 times, i.e.::

(lldb) br set -i 84 -n GlobalARCOpts::run

A final trick is that one can use the -R option to stop at a relative assembly
address in lldb. Specifically, lldb resolves the breakpoint normally and then
just adds the argument -R to the address. So for instance, if I want to stop at
the address at +38 in the function with the name 'foo', I would write::

(lldb) br set -R 38 -n foo

Then lldb would add 38 to the offset of foo and break there. This is really
useful in contexts where one wants to set a breakpoint at an assembly address
that is stable across multiple different invocations of lldb.

LLDB Scripts
~~~~~~~~~~~~

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