Fix SFINAE usage in insert and do_intersect functions on Ubuntu 24.04

[ViNN280801]

Summary of Changes

I fixed an error in the code related to the incorrect use of std::is_same. In the source code, there was an attempt to use std::is_some<int, int>::type as a function parameter, which caused a compilation error. I removed this unnecessary parameter and added type checking using SFINAE (std::enable_if).
I have Ubuntu 24.04:

loveit0@loveit0-Nitro-AN515-58:~$ uname -a
Linux loveit0-Nitro-AN515-58 6.11.0-17-generic #17~24.04.2-Ubuntu SMP PREEMPT_DYNAMIC Mon Jan 20 22:48:29 UTC 2 x86_64 x86_64 x86_64 GNU/Linux

I used the CGAL in my project for intersections with AABB and when I compiling my code, I faced with these kind of errors:

/usr/local/include/CGAL/Arrangement_2/Arrangement_on_surface_2_global.h:145:27: error: ‘std::is_same<__remove_cv(int), int>::type’ is not a type
  145 |             const PointLocation& pl, ZoneVisitor &visitor,
      |                           ^~~
/usr/local/include/CGAL/Arrangement_2/Arrangement_on_surface_2_global.h:471:27: error: ‘std::is_same<__remove_cv(int), int>::type’ is not a type
  471 |             InputIterator begin, InputIterator end,
      |                           ^~~
/usr/local/include/CGAL/Arrangement_2/Arrangement_on_surface_2_global.h:1534:5: error: ‘std::is_same<__remove_cv(int), int>::type’ is not a type
 1534 |              const PointLocation& pl, std::is_same<int, int>::type)
      |     ^  

Release Management

• Affected package(s): Arrangement_on_surface_2
• Issue(s) solved (if any): -
• Feature/Small Feature (if any): N/A
• License and copyright ownership: This contribution is licensed under the terms used by CGAL, and the authorship remains with the contributors.

[sloriot]

Thanks for the PR! Do you have an example that we could compile and that is showing the error?

[ViNN280801]

I don't know why, but it occurs in yours code when I am compiling my code

But when I making minimal example with do_intersect:

main.cpp

#include <CGAL/Exact_predicates_exact_constructions_kernel.h>
#include <CGAL/intersections.h>

using Kernel = CGAL::Exact_predicates_inexact_constructions_kernel;
using Point = Kernel::Point_3;
using Segment = Kernel::Segment_3;
using Triangle = Kernel::Triangle_3;

int main()
{
    Segment segment(Point(0, 0, 0), Point(1, 1, 1));
    Triangle triangel(Point(0, 0, 0), Point(1, 0, 0), Point(0, 1, 0));
    bool intersects = CGAL::do_intersect(segment, triangel);

    return 0;
}

main.cpp

cmake_minimum_required(VERSION 3.10)
project(example)

# GMP Setup
find_path(GMP_INCLUDE_DIR gmp.h HINTS /usr/include/x86_64-linux-gnu
                                      /usr/include/CGAL)
find_library(
  GMP_LIBRARY
  NAMES gmp libgmp
  HINTS /usr/lib/x86_64-linux-gnu)
if(NOT GMP_INCLUDE_DIR OR NOT GMP_LIBRARY)
  message(FATAL_ERROR "GMP not found. Please ensure GMP is installed.")
endif()
include_directories(${GMP_INCLUDE_DIR})
link_libraries(${GMP_LIBRARY})

# CGAL Setup
find_package(CGAL REQUIRED)

# Compile
add_executable(example main.cpp)

of course it compiles successfully:

If you need to get error like me, you can compile my repo Start or I can try to make minimal example, but I need time😬

[ViNN280801]

and I really don't understand why I have errors in CGAL header file
/usr/local/include/CGAL/Arrangement_2/Arrangement_on_surface_2_global.h
it's really strange, and the one thing that helps me is add SFINAE using std::enable_if_t:

1. Changing No 1

template <typename GeometryTraits_2, typename TopologyTraits,
         typename PointLocation, typename ZoneVisitor>
void insert(Arrangement_on_surface_2<GeometryTraits_2, TopologyTraits>& arr,
           const typename GeometryTraits_2::X_monotone_curve_2& c,
           const PointLocation& pl, ZoneVisitor &visitor,
           std::is_same<int, int>::type)

to

template <typename GeometryTraits_2, typename TopologyTraits,
          typename PointLocation, typename ZoneVisitor,
          typename = std::enable_if_t<std::is_same<PointLocation, int>::value>>
void insert(Arrangement_on_surface_2<GeometryTraits_2, TopologyTraits>& arr,
            const typename GeometryTraits_2::X_monotone_curve_2& c,
            const PointLocation& pl, ZoneVisitor &visitor)

2. Changing No 2

template <typename GeometryTraits_2, typename TopologyTraits,
          typename InputIterator>
void insert(Arrangement_on_surface_2<GeometryTraits_2, TopologyTraits>& arr,
            InputIterator begin, InputIterator end,
            std::is_same<int, int>::type)

to

template <typename GeometryTraits_2, typename TopologyTraits,
          typename InputIterator,
          typename = std::enable_if_t<std::is_same<InputIterator, int>::value>>
void insert(Arrangement_on_surface_2<GeometryTraits_2, TopologyTraits>& arr,
            InputIterator begin, InputIterator end)

3. Changing No 3

template <typename GeometryTraits_2, typename TopologyTraits,
          typename PointLocation>
bool
do_intersect(Arrangement_on_surface_2<GeometryTraits_2, TopologyTraits>& arr,
             const typename GeometryTraits_2::X_monotone_curve_2& c,
             const PointLocation& pl, std::is_same<int, int>::type)

to

template <typename GeometryTraits_2, typename TopologyTraits,
          typename PointLocation,
          typename = std::enable_if_t<std::is_same<PointLocation, int>::value>>
bool
do_intersect(Arrangement_on_surface_2<GeometryTraits_2, TopologyTraits>& arr,
             const typename GeometryTraits_2::X_monotone_curve_2& c,
             const PointLocation& pl)

And only after I changed this file, everything compiled successfully for me. Maybe my case is single or maybe I configured smth wrong, don't know exactly.

[ViNN280801]

btw, tests are successfull

[efifogel]

I would also like to have a look at the fix. I'll do it next week. BW, perhaps you mentioned it and I missed it: which version of compiler are you using?

…

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[ViNN280801]

my project uses CUDA, so, I used nvcc_wrapper from kokkos
but what about gcc/g++