42 lines
1.6 KiB
ReStructuredText
42 lines
1.6 KiB
ReStructuredText
Ok, so your nice Nim program crashes under various hard-to-reproduce conditions. What can you do about that?
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Test with different GCs
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=======================
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* ``--gc:boehm``
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* ``--gc:refc``
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* ``--gc:markAndSweep``
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Note that if your program does not crash with a different GC, it doesn't imply you found a GC bug! It's just a weak indicator.
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Test under different OSes
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=========================
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* Linux
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* MacOS X
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* Windows
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Test under different CPUs
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=========================
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* i386 (32bit)
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* amd64 (64bit)
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* arm
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Test different compiler options
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===============================
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``-d:release`` vs debug mode is the obvious choice, but the Nim GC, allocator and standard library have many more checks you can should enable:
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| -d:useSysAssert enables assertions in the system.nim, especially in Nim's allocator.
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| -d:useGcAssert enables assertions in Nim's GC.
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| -d:nimBurnFree overwrite deallocated memory with 0xff bytes so that "access after free" triggers a segfault.
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Edit lib/system/mmdisp.nim and gc.nim
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=====================================
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Even more debugging options can be enabled by editing ``lib/system/mmdisp.nim``. Most of these have no ``--define`` equivalent, unfortunately.
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One problem with corruptions is their non-deterministic nature, in particular heap and stack addresses change from run to run. Define ``-d:corruption`` to enable "cell IDs", so that every "cell" (that is every ``ref``/``string``/``seq``) gets a unique ID. It's often interesting to see if the corrupted cell has the same ID from run to run or if it differs. If it differs the bug is non-deterministic. Within the GC ``writeCell`` can be used to output offending cells.
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