## Summary
This PR adds a new debugging utility `bisect_failures` to the
STL_Extension package. This function helps identify minimal failing test
cases from complex input data by using a bisection-like approach.
**Small feature: [bisect failures debugging
utility](https://cgalwiki.geometryfactory.com/CGAL/Members/wiki/Features/Small_Features/bisect_failures_debugging_utility)**
## Features
- **Multiple failure type support**: Handles CGAL exceptions,
std::exceptions, and exit codes
- **Automatic granularity adjustment**: Starts with ratio=0.5,
automatically halves when no fault is found
- **Debug output**: Saves intermediate states (`current`, `bad`,
`error`, `final_bad`)
- **Template-based design**: Works with any copyable/assignable data
type
## Testing
Added comprehensive test suite (`test_bisect_failures.cpp`) with 14
tests:
- ✅ Edge cases (empty data, no failures)
- ✅ Single element failures (CGAL exception, std::exception, exit code)
- ✅ Pair combinations (all 2-element permutations)
- ✅ Triple combinations (all 3 failure types together)
All tests pass in both Debug and Release configurations.
## Use Case
This utility is particularly useful for:
- Debugging complex geometric algorithms with large input datasets
- Finding minimal reproducible test cases from failing inputs
- Isolating problematic elements in mesh processing, triangulation, etc.
## Example Usage
```cpp
auto get_size = [](const Mesh& m) { return m.number_of_faces(); };
auto simplify = [](Mesh& m, std::size_t start, std::size_t end) -> bool {
// Remove faces from start to end
for(std::size_t i = start; i < end && i < m.number_of_faces(); ++i) {
m.remove_face(start);
}
return true;
};
auto run = [](const Mesh& m) -> int { return algorithm(m); };
auto save = [](const Mesh& m, const std::string& prefix) {
std::ofstream out(prefix + ".off");
out << m;
};
int result = bisect_failures(mesh, get_size, simplify, run, save);
```
## Files Changed
- `STL_Extension/include/CGAL/bisect_failures.h` (new) - Main utility
header
- `STL_Extension/test/STL_Extension/test_bisect_failures.cpp` (new) -
Test suite
- `STL_Extension/test/STL_Extension/CMakeLists.txt` (modified) - Added
test
## Checklist
- [x] Code compiles without errors (Debug and Release)
- [x] All tests pass
- [x] Comprehensive documentation with Doxygen comments
- [x] Example usage in documentation
- [x] Follows CGAL coding style conventions
- [x] Deal with false positive in the testsuite
## Release Management
* Affected package(s): `STL_Extension`
* Feature/Small Feature (if any): [bisect failures debugging
utility](https://cgalwiki.geometryfactory.com/CGAL/Members/wiki/Features/Small_Features/bisect_failures_debugging_utility)
* Link to compiled documentation (obligatory for small feature)
[doc](https://cgal.github.io/9118/v2/STL_Extension/group__PkgSTLExtensionUtilities.html#gad56d708faac9063d3de057394a6d8c52)
* License and copyright ownership: no change
Sebastien Loriot
244d9dee08