BinaryCacheStore::narFromPath(): Fix unreachable code #14643
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When this function is called as a coroutine (e.g. when it's called by `copyStorePath()`), the code after `decompressor->finish()` is never reached because the coroutine is destroyed when the caller reaches the end of the NAR. So put that code in a `LambdaSink` destructor.
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Ericson2314
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Nov 25, 2025
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This looks good to me, but I would like @xokdvium to give it a quick glance
xokdvium
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Nov 25, 2025
| stats.narRead++; | ||
| // stats.narReadCompressedBytes += nar->size(); // FIXME | ||
| stats.narReadBytes += narSize.length; | ||
| // Note: don't do anything here because it's never reached if we're called as a coroutine. |
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But if this code doesn't run then how is the destructor (for LambdaSink) being run? Would be nice to add a unit test for the issue so it's more clear what's being fixed
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Boost unwinds the coroutine stack by throwing an exception of type boost::context::detail::forced_unwind. So destructors of stack variables do get executed.
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Motivation
When this function is called as a coroutine (e.g. when it's called by
copyStorePath()), the code afterdecompressor->finish()is never reached because the coroutine is destroyed when the caller reaches the end of the NAR. So put that code in aLambdaSinkdestructor.Context
Noticed while doing DeterminateSystems#279.
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