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Add info about debugging during julia's bootstrap
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Stolen from @ihnorton, https://groups.google.com/d/msg/julia-dev/s7T5DvPXcU4/cM21ikIWW7YJ
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@timholy
timholy committed Apr 29, 2015
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Expand Up @@ -74,6 +74,23 @@ Calling a particular method

Since this function is used for every call, you will make everything 1000x slower if you do this.

Debugging during julia's build process (bootstrap)
--------------------------------------------------

Errors that occur during ``make`` need special handling. Julia is built in two stages, constructing
``sys0`` and ``sys.ji``. To see what commands are running at the time of failure, use ``make VERBOSE=1``.

At the time of this writing, you can debug build errors during the ``sys0`` phase from the ``base``
directory using::

julia/base$ gdb --args ../usr/bin/julia-debug -C native --build ../usr/lib/julia/sys0 sysimg.jl

You might need to delete all the files in ``usr/lib/julia/`` to get this to work.

You can debug the ``sys.ji`` phase using::

julia/base$ gdb --args .../usr/bin/julia-debug -C native --build ../usr/lib/julia/sys -J ../usr/lib/julia/sys0.ji sysimg.jl

Mozilla's Record and Replay Framework (rr)
---------------------------------------------

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3 comments on commit c991a23

@ihnorton
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Jameson pointed out that the full path to sysimg is no longer necessary, so you can do julia -C native --build sys sysimg.jl (or sys0)

@ihnorton
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Also, I try to avoid debugging bootstrap at all costs now:

@timholy
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You're my new best friend. This hadn't penetrated my consciousness yet, so thanks for the reminder about its existence!

For what I'm doing now, the old way isn't too bad, because almost all of my changes are to the C code (which, paradoxically, is in a few ways easier because building is so much faster). But for the future, I'm totally sold on this.

I'll add a version of this to the docs.

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