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Merged
Onwcan merged 2 commits into from
Sep 13, 2026
Merged

docs: document compile-time limits #5

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ad142a5
docs: document compile-time limits
Sep 12, 2026
a98fc5f
test: keep documented limits in sync
Sep 13, 2026
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12 changes: 12 additions & 0 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -63,6 +63,18 @@ scripts/format.sh
It pins clang-format 18; a different major version formats differently and CI
will reject the result.

## Compile-time limits

motionkit uses fixed-size storage to keep its core algorithms allocation-free.
The following public limits are intentionally fixed and cannot currently be
overridden through CMake:

| Constant | Defining header | Limit |
|---|---|---:|
| `kMaxPathKnots` | `motionkit/core/cartesian.hpp` | 65 |
| `kMaxWaypoints` | `motionkit/core/cartesian.hpp` | 16 |
| `kMaxObstacles` | `motionkit/core/collision.hpp` | 32 |

## Use it downstream

```cmake
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6 changes: 6 additions & 0 deletions tests/CMakeLists.txt
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Expand Up @@ -10,6 +10,12 @@ FetchContent_MakeAvailable(googletest)

include(GoogleTest)

add_test(NAME readme_limits
COMMAND ${CMAKE_COMMAND}
-DPROJECT_SOURCE_DIR=${PROJECT_SOURCE_DIR}
-P ${CMAKE_CURRENT_SOURCE_DIR}/check_readme_limits.cmake)
set_tests_properties(readme_limits PROPERTIES LABELS unit)

add_executable(motionkit_tests
test_vec3.cpp
test_so3.cpp
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19 changes: 19 additions & 0 deletions tests/check_readme_limits.cmake
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@@ -0,0 +1,19 @@
file(READ "${PROJECT_SOURCE_DIR}/README.md" readme)

function(check_limit name header)
file(READ "${PROJECT_SOURCE_DIR}/include/${header}" declaration)
string(REGEX MATCH "${name} = ([0-9]+)" match "${declaration}")
if(NOT match)
message(FATAL_ERROR "Could not find ${name} in ${header}")
endif()
set(value "${CMAKE_MATCH_1}")
string(FIND "${readme}" "| `${name}` | `${header}` | ${value} |" documented)
if(documented EQUAL -1)
message(FATAL_ERROR
"README limit for ${name} does not match ${header} (${value})")
endif()
endfunction()

check_limit(kMaxPathKnots motionkit/core/cartesian.hpp)
check_limit(kMaxWaypoints motionkit/core/cartesian.hpp)
check_limit(kMaxObstacles motionkit/core/collision.hpp)
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