[mikomikotaishi]

This PR adds support for C++20 modules, which can be enabled if the version of C++ is at least C++20 (and is opt-in, therefore not raising the minimum C++ version). It is enabled using JSONCPP_WITH_MODULE and creates a module jsoncpp.

[greptile-apps]

Confidence Score: 4/5

[Medium impact] The PR adds an optional module path for CMake users.

The installed package needs module export information before this is safe to merge.

Findings

1.  Installed module imports fail ▶

Summary

Adds an opt-in C++20 module named jsoncpp.

• CMake builds JsonCpp as an importable C++20 module when enabled.

_{Reviews (5) · Last reviewed commit: "Address Greptile suggestions for module ..." · Reviewed by Greptile}

[coveralls]

Coverage Report for CI Build 40347579800

Coverage remained the same at 89.926%

Details

• Coverage remained the same as the base build.
• Patch coverage: No coverable lines changed in this PR.
• No coverage regressions found.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

No coverage regressions found.

---

Coverage Stats

Relevant Lines:	2740
Covered Lines:	2615
Line Coverage:	95.44%
Relevant Branches:	2640
Covered Branches:	2223
Branch Coverage:	84.2%
Branches in Coverage %:	Yes
Coverage Strength:	23835.16 hits per line

---

💛 - Coveralls

[greptile-apps]

Installed module imports fail

This installs the module source, but the existing install(EXPORT jsoncpp ...) call does not write the information CMake needs to connect import jsoncpp to that source. A separate project can find and link jsoncpp::module but cannot compile code that imports it. Add CXX_MODULES_DIRECTORY to the package export when modules are enabled.

Knowledge Base Used: Consumer package integration