java-topology/defects/cmake/cmake-0003-addruntimedll-ticket.md

cmake-0003 — AddRuntimeDLL: O(n) std::find per DLL in hot loop

Severity: MEDIUM File: Source/cmComputeLinkInformation.cxx Lines: 1352–1355 CWE: CWE-407 (Algorithmic Complexity — Quadratic)

Description

AddRuntimeDLL() guards insertion with a linear scan over RuntimeDLLs:

// Source/cmComputeLinkInformation.cxx:1352-1355
if (std::find(this->RuntimeDLLs.begin(), this->RuntimeDLLs.end(), tgt) ==
    this->RuntimeDLLs.end()) {
  this->RuntimeDLLs.emplace_back(tgt);
}

AddRuntimeDLL is called from AddItem() and AddSharedDepItem(), both of which are invoked for every link entry in the Compute() main loop over linkEntries. On a Windows/DLL project with D shared-library dependencies, the total cost is O(D²) pointer comparisons.

Fix

Add a parallel std::unordered_set<cmGeneratorTarget const*> RuntimeDLLsSet member. Replace the std::find guard with a set insertion check.

Patch: patch/cmake-0003-addruntimedll-unordered-set.patch Unit test: unit/RuntimeDllAlgorithm.java

Complexity

	Time
Before	O(D²)
After	O(D) amortised