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    GeoffWozniak avatar GeoffWozniak 1 year ago | link | on: When Debuggers Lie

    Part of the reason why it took us awhile to debug our issue was that we assumed that the stack trace we saw was accurate.

    Recall how it was compiled:

    clang -std=c99 -O3 -g -o inline_merge inline_merge.c

    As the GCC manual says with respect to combinging O with g: “The shortcuts taken by optimized code may occasionally produce surprising results.”

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      kyrias avatar kyrias 1 year ago | link

      And relatedly from the clang man page:

      Note that Clang debug information works best at -O0.

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        LibertarianLlama avatar LibertarianLlama 1 year ago | link

        So one should recompile for the purpose of debugging?

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          tbodt avatar tbodt 1 year ago | link

          Yes.

          GCC has -Og, which turns on all optimizations that can’t affect debugging.

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            apy avatar apy 1 year ago | link

            Or design your software in such a way that the stacktrace is not needed for debugging. Which is hard, for sure, but the current trend of depending on stacktraces for everything (Java, Python, for example) is a bit too extreme IMO. For a comparison, in Ocaml I tend to use a result type monad for things that can fail at which point the compiler makes sure I do something with all errors.