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Debugging the Nim compiler

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Mamy Ratsimbazafy edited this page Apr 25, 2019 · 1 revision

Due to Nimbus sometimes using niche features of the Nim compiler, we might encounter compiler crashes or semantic check errors with no clue how to proceed forward and a lot of difficulty to create a minimal test case.

2 strategies to kickstart an investigation are available. The first one is to compile a Nim compiler with stack traces enabled.

Nim compiler with stack traces

  1. Clone Nim and build koch as in the Nim readme.
  2. Create a temporary Nim compiler with stacktraces, for example to debug https://github.com/status-im/nimbus/issues/322, this is the command to reproduce the bug: 
    ./koch temp c -r -o:build/gascosts ../../Status/nimbus/tests/all_tests.nim # Replace by your own path

Bisecting

You can use git bisect to narrow down the offending commit. Usually only koch boot -d:release is needed to rebuild bin/nim but sometimes you need to re-bootstrap the koch and potentially the csources

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