[cmake-developers] [CMake 0015723]: Regression: FindCUDA fails for C++ only projects in CMake 3.3.1 due find_package(Threads), while it works well in CMake 3.2.3

[Mantis Bug Tracker]

The following issue has been SUBMITTED. 
====================================================================== 
http://www.cmake.org/Bug/view.php?id=15723 
====================================================================== 
Reported By:                Adam Strzelecki
Assigned To:                
====================================================================== 
Project:                    CMake
Issue ID:                   15723
Category:                   CMake
Reproducibility:            always
Severity:                   major
Priority:                   normal
Status:                     new
====================================================================== 
Date Submitted:             2015-09-02 06:31 EDT
Last Modified:              2015-09-02 06:31 EDT
====================================================================== 
Summary:                    Regression: FindCUDA fails for C++ only projects in
CMake 3.3.1 due find_package(Threads), while it works well in CMake 3.2.3
Description: 
CUDA language is C++ superset, so developers may prefer using C++ only project
together with CUDA. FindCUDA already supports such case (1) when neither
CUDA_HOST_COMPILER nor CMAKE_C_COMPILER is defined, just skips adding --ccbin.

Another case (2) is that user defined its own CUDA_HOST_COMPILER that is
different than CMAKE_C_COMPILER, then custom host compiler is passed to --ccbin.

The problem is that recently CUDA_USE_STATIC_CUDA_RUNTIME (default ON) started
calling find_package(Threads REQUIRED) that tries to lookup pthread using
CMAKE_C_COMPILER which is invalid in both cases (1) (2).

However I don't see any clear solution here. I understand that linking CUDA
static rt requires pthread linkage, but maybe we should just check if current
linker can either link -lpthread or -pthread, rather falling back to C compiler
that may be undefined for the project?


Steps to Reproduce: 
# CMakeList.txt
cmake_minimum_required(VERSION 2.6)
project(OnlyCXXCUDA CXX)
find_package(CUDA)


$ cmake .
-- The CXX compiler identification is AppleClang 7.0.0.7000059
-- Check for working CXX compiler:
/Applications/Xcode-beta.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/c++
-- Check for working CXX compiler:
/Applications/Xcode-beta.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/c++
-- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Looking for include file pthread.h
CMake Error at
/Applications/CMake.app/Contents/share/cmake-3.3/Modules/CheckIncludeFiles.cmake:79
(try_compile):
  Unknown extension ".c" for file

   
/Users/ono/Documents/Bugs/CMake/FindCUDA/CMakeFiles/CMakeTmp/CheckIncludeFiles.c

  try_compile() works only for enabled languages.  Currently these are:

    CXX

  See project() command to enable other languages.
Call Stack (most recent call first):
  /Applications/CMake.app/Contents/share/cmake-3.3/Modules/FindThreads.cmake:123
(CHECK_INCLUDE_FILES)
  /Applications/CMake.app/Contents/share/cmake-3.3/Modules/FindCUDA.cmake:741
(find_package)
  CMakeLists.txt:3 (find_package)


-- Looking for include file pthread.h - not found
CMake Error at
/Applications/CMake.app/Contents/share/cmake-3.3/Modules/FindPackageHandleStandardArgs.cmake:148
(message):
  Could NOT find Threads (missing: Threads_FOUND)
Call Stack (most recent call first):
 
/Applications/CMake.app/Contents/share/cmake-3.3/Modules/FindPackageHandleStandardArgs.cmake:388
(_FPHSA_FAILURE_MESSAGE)
  /Applications/CMake.app/Contents/share/cmake-3.3/Modules/FindThreads.cmake:204
(FIND_PACKAGE_HANDLE_STANDARD_ARGS)
  /Applications/CMake.app/Contents/share/cmake-3.3/Modules/FindCUDA.cmake:741
(find_package)
  CMakeLists.txt:3 (find_package)


-- Configuring incomplete, errors occurred!
See also "/Users/ono/Documents/Bugs/CMake/FindCUDA/CMakeFiles/CMakeOutput.log".
See also "/Users/ono/Documents/Bugs/CMake/FindCUDA/CMakeFiles/CMakeError.log".

====================================================================== 

Issue History 
Date Modified    Username       Field                    Change               
====================================================================== 
2015-09-02 06:31 Adam StrzeleckiNew Issue                                    
======================================================================