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Add c++20 compile option #6391

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Add c++20 compile option #6391

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10 changes: 6 additions & 4 deletions CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -5,19 +5,21 @@ cmake_minimum_required(VERSION 3.16.3 FATAL_ERROR)
set(CMAKE_CXX_STANDARD 17 CACHE STRING "The target C++ standard. PCL requires C++14 or higher.")
set(CMAKE_CXX_STANDARD_REQUIRED ON)
set(CMAKE_CXX_EXTENSIONS OFF)
if("${CMAKE_CXX_STANDARD}" GREATER_EQUAL 17)
set(PCL_CXX_COMPILE_FEATURES cxx_std_17)
if("${CMAKE_CXX_STANDARD}" GREATER_EQUAL 20)
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Copilot AI Jan 14, 2026

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The condition GREATER_EQUAL 20 will match C++ standards beyond C++20 (such as C++23, C++26, etc.), but sets C++20-specific values for PCL__cplusplus (202002L) and PCL_REQUIRES_MSC_VER (1928). This creates an inconsistency: if a user sets CMAKE_CXX_STANDARD to 23, line 21 would set PCL_CXX_COMPILE_FEATURES to cxx_std_23, but PCL__cplusplus would remain at the C++20 value (202002L). This could cause incorrect compiler version checks in pcl_config.h.in. Consider either changing to EQUAL 20 with additional conditions for newer standards, or update the values to be appropriate for the highest standard being checked.

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if("${CMAKE_CXX_STANDARD}" GREATER_EQUAL 20)
if("${CMAKE_CXX_STANDARD}" EQUAL 20)

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@larshg larshg Jan 14, 2026

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This one we can just leave as is. PCL__cplusplus is only used to check for a minimum requirement.

set(PCL__cplusplus 202002L)
set(PCL_REQUIRES_MSC_VER 1928)
elseif("${CMAKE_CXX_STANDARD}" EQUAL 17)
set(PCL__cplusplus 201703L)
set(PCL_REQUIRES_MSC_VER 1912)
elseif("${CMAKE_CXX_STANDARD}" EQUAL 14)
set(PCL_CXX_COMPILE_FEATURES cxx_std_14)
set(PCL__cplusplus 201402L)
set(PCL_REQUIRES_MSC_VER 1900)
else()
message(FATAL_ERROR "Unknown or unsupported C++ standard specified")
endif()

set(CMAKE_CUDA_STANDARD 17 CACHE STRING "The target CUDA/C++ standard. PCL requires CUDA/C++ 14 or higher.")
set(PCL_CXX_COMPILE_FEATURES cxx_std_${CMAKE_CXX_STANDARD})
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The CMAKE_CUDA_STANDARD is no longer defined as a CACHE variable. While the PR description explains this enforces synchronization with CMAKE_CXX_STANDARD to prevent compilation issues, this is a breaking change for users who were previously setting CMAKE_CUDA_STANDARD separately via CMake command line (e.g., -DCMAKE_CUDA_STANDARD=20). Their setting will now be ignored. Consider documenting this breaking change in release notes or migration guides, or alternatively, implementing a check that warns users if they attempt to set CMAKE_CUDA_STANDARD to a different value than CMAKE_CXX_STANDARD.

Suggested change
set(PCL_CXX_COMPILE_FEATURES cxx_std_${CMAKE_CXX_STANDARD})
set(PCL_CXX_COMPILE_FEATURES cxx_std_${CMAKE_CXX_STANDARD})
# Warn users if they attempted to set CMAKE_CUDA_STANDARD independently; it is
# intentionally synchronized with CMAKE_CXX_STANDARD in this project.
if(DEFINED CMAKE_CUDA_STANDARD AND NOT CMAKE_CUDA_STANDARD STREQUAL "${CMAKE_CXX_STANDARD}")
message(WARNING
"CMAKE_CUDA_STANDARD is synchronized with CMAKE_CXX_STANDARD in this project. "
"The provided CMAKE_CUDA_STANDARD ('${CMAKE_CUDA_STANDARD}') will be ignored in "
"favor of CMAKE_CXX_STANDARD='${CMAKE_CXX_STANDARD}'.")
endif()

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@larshg larshg Jan 14, 2026

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This one we could consider adding.

set(CMAKE_CUDA_STANDARD ${CMAKE_CXX_STANDARD})
set(CMAKE_CUDA_STANDARD_REQUIRED ON)

set(CMAKE_CONFIGURATION_TYPES "Debug;Release" CACHE STRING "possible configurations" FORCE)
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