Clarify ConstSharedPtr achieves zero-copy - #7064
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August 13, 2026 10:31
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Re-add the plain const T & callback type to the list of subscriber signatures that do not achieve zero-copy, addressing reviewer feedback that this case was dropped from the previous clarification. Co-Authored-By: MShields1986 <matthew.shields@dexory.com>
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Description
The existing note on subscriber callback types incorrectly implied that no
shared_ptrvariant could achieve zero-copy, grouping mutableshared_ptr<T>andConstSharedPtrtogether.This is misleading:
const std::shared_ptr<const T> &(ConstSharedPtr) uses immutable shared ownership and delivers zero-copy to multiple intra-process subscribers simultaneously, making it the correct pattern for one-to-many composition.Changes:
shared_ptrsentence in the two-node pipeline section to distinguishConstSharedPtr(zero-copy capable) from mutableshared_ptr<T>(not zero-copy)ConstSharedPtrcallbacks avoid the fan-out copy penalty thatUniquePtrincurs in one-to-many graphsA more detailed write up with tests and findings is available here
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Additional Information
The correction to the
shared_ptrnote is a factual fix as the previous wording could lead readers to incorrectly avoidConstSharedPtrin one-to-many scenarios where it is the appropriate tool.