[C++] Fix Undefined behavior for zero length vectors #5355
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include/flatbuffers/flatbuffers.h
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| void push(const uint8_t *bytes, size_t num) { | ||
| memcpy(make_space(num), bytes, num); | ||
| // CreateVector above, can pass through a nullptr for bytes |
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If so, lets make the fix in CreateVector, not here. This is performance sensitive code, so I would like as few if-thens (or as far from the core) as possible.
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OK, are there benchmarks as part of the project I can run to see if there will be impact from my changes?
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No there aren't. There are some super old benchmarks in a branch that are win32 only.
Regardless, if you can pull an if-then further away from a hot function, why not do it? especially when all other callers of this function already comply with memcpy's rules?
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I think its fine, just wondering if I can assess the impact further upstream. I will update the PR in the next day or two. Thank you for the feedback.
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@aardappel appveyor failures look unrelated to this change, but I'm not too familiar with the build, please let me know if you think this broke something? |
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Yes, CI looks unrelated. |
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UBSan fails when checking for nullability with clang in this header file without this change.