Four orthogonal opt-in build modes on top of the existing PCH + Unity
defaults. Each addresses a specific iteration scenario; defaults are
unchanged (PCH + Unity stays the canonical fast full-rebuild path).
(A) HEADERS_CHECK target — opt-in via -DCONFORMALLAB_HEADERS_CHECK=ON
Per-public-header smoke-compile sentinels. For each of the six
public CGAL umbrella headers, a stub TU `#include <…>\nint main(){}`
is generated at configure time and compiled in isolation.
* Full headers_check build: ≈ 12 s
* Incremental after touching one header: ≈ 0.1 s
Use case: "did my refactor still parse the public API?" without
waiting 55 s for the full CGAL test build.
(C) DEV_BUILD mode — opt-in via -DCONFORMALLAB_DEV_BUILD=ON
PCH stays on; Unity Build is forced off (both globally AND on the
cgal-tests target which previously overrode the global setting).
Trade-off: full clean rebuild ~75 s (+36 % vs the 55 s default)
but incremental rebuild after editing a single test file drops
from ~46 s (unity batch) to ~16 s (single TU + relink).
Flip on for trial-and-error sessions, flip off before measuring
CI build time or shipping a PR.
(D) ccache integration — default ON, disable with -DCONFORMALLAB_USE_CCACHE=OFF
Detects `ccache` on PATH and prepends it to compile + link
launchers. On Apple clang + PCH + Unity the macOS-local hit
rate is currently 0 % (3 separate friction points documented
in doc/architecture/compile-time.md § "ccache — honesty notes");
stays neutral when it doesn't help. Real payoff on Linux CI
(g++ + traditional PCH) where 80 %+ hit rates are typical.
(BUILD_TESTING=OFF) Standard CMake gate, now respected end-to-end.
Wrapped both `add_subdirectory(tests)` AND the FetchContent of
GoogleTest in `if(BUILD_TESTING)`. Pass `-DBUILD_TESTING=OFF`:
* Configure ≈ 1 s
* Build ≈ 0 s
* 0 object files
* No GTest fetch
Use case: IDE-syntax-check workflow that needs
`compile_commands.json` but does NOT need to download GTest
or build any test binary.
doc/architecture/compile-time.md gains:
* a "Workflow modes — what to choose when" section with a 4-row
switch matrix and a "mode matrix at a glance" comparison table
* a ccache honesty-notes block listing the three macOS friction
points (PCH artefact caching, Unity Build path randomisation,
CMake launcher integration) — Linux CI is where the lever pays
off
Verified: default build 53 s wall, 236/236 tests pass; all opt-in
modes tested end-to-end with their expected workflow numbers
documented in the doc.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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