64c9ee98b7
Otherwise we'd panic with a stack overflow. Most programs are in control of the data being encoded and can ensure there are no cycles, but sometimes it's not that simple. For example, running a user's html template with script tags can easily result in crashes if the user can find a pointer cycle. Adding the checks via a map to every ptrEncoder.encode call slowed down the benchmarks below by a noticeable 13%. Instead, only start doing the relatively expensive pointer cycle checks if we're many levels of pointers deep in an encode state. A threshold of 1000 is small enough to capture pointer cycles before they're a problem (the goroutine stack limit is currently 1GB, and I needed close to a million levels to reach it). Yet it's large enough that reasonable uses of the json encoder only see a tiny 1% slow-down due to the added ptrLevel field and check. name old time/op new time/op delta CodeEncoder-8 2.34ms ± 1% 2.37ms ± 0% +1.05% (p=0.000 n=10+10) CodeMarshal-8 2.42ms ± 1% 2.44ms ± 0% +1.10% (p=0.000 n=10+10) name old speed new speed delta CodeEncoder-8 829MB/s ± 1% 820MB/s ± 0% -1.04% (p=0.000 n=10+10) CodeMarshal-8 803MB/s ± 1% 795MB/s ± 0% -1.09% (p=0.000 n=10+10) name old alloc/op new alloc/op delta CodeEncoder-8 43.1kB ± 8% 42.5kB ±10% ~ (p=0.989 n=10+10) CodeMarshal-8 1.99MB ± 0% 1.99MB ± 0% ~ (p=0.254 n=9+6) name old allocs/op new allocs/op delta CodeEncoder-8 0.00 0.00 ~ (all equal) CodeMarshal-8 1.00 ± 0% 1.00 ± 0% ~ (all equal) Finally, add a few tests to ensure that the code handles the edge cases properly. Fixes #10769. Change-Id: I73d48e0cf6ea140127ea031f2dbae6e6a55e58b8 Reviewed-on: https://go-review.googlesource.com/c/go/+/187920 Run-TryBot: Daniel Martí <mvdan@mvdan.cc> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Bjørn Erik Pedersen <bjorn.erik.pedersen@gmail.com> Reviewed-by: Andrew Bonventre <andybons@golang.org> |
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