[SOLVED] Clang error while compiling Sofa

[Simit]

Hello,

I am trying to build SOFA v20.06 and I have followed all the instructions on this page: https://www.sofa-framework.org/community/doc/getting-started/build/linux/

I am using clang-7 and cmake 3.19. During the ninja build I am getting the below error

[157/1552] Building CXX object SofaKernel/SofaFramework/SofaHel...r/CMakeFiles/SofaHelper.dir/src/sofa/helper/AdvancedTimer.cpp.o
FAILED: SofaKernel/SofaFramework/SofaHelper/CMakeFiles/SofaHelper.dir/src/sofa/helper/AdvancedTimer.cpp.o 
/usr/bin/clang++-7 -DNDEBUG -DSOFA_BUILD_HELPER -DSOFA_BUILD_SOFAHELPER -DSofaHelper_EXPORTS -I/home/one/Projects/sofa/src/SofaKernel/modules/SofaHelper/src -I/home/one/Projects/sofa/src/SofaKernel/modules/SofaHelper/../SofaSimulationCore/src -I/home/one/Projects/sofa/src/SofaKernel/modules/SofaHelper/../SofaDefaultType/src -I/home/one/Projects/sofa/src/SofaKernel/modules/SofaHelper/../SofaCore/src -Iinclude/SofaFramework -Iinclude/GTest -isystem /home/one/Projects/sofa/src/SofaKernel/extlibs/json -isystem /home/one/Projects/sofa/src/extlibs/gtest/include -isystem /usr/include/eigen3 -Wall -W -Wno-padded -O3 -DNDEBUG -fPIC -DFRAMEWORK_TEST_RESOURCES_DIR=\"/home/one/Projects/sofa/src/SofaKernel/SofaFramework/resources/tests\" -pthread -DGTEST_LINKED_AS_SHARED_LIBRARY=1 -std=gnu++17 -MD -MT SofaKernel/SofaFramework/SofaHelper/CMakeFiles/SofaHelper.dir/src/sofa/helper/AdvancedTimer.cpp.o -MF SofaKernel/SofaFramework/SofaHelper/CMakeFiles/SofaHelper.dir/src/sofa/helper/AdvancedTimer.cpp.o.d -o SofaKernel/SofaFramework/SofaHelper/CMakeFiles/SofaHelper.dir/src/sofa/helper/AdvancedTimer.cpp.o -c /home/one/Projects/sofa/src/SofaKernel/modules/SofaHelper/src/sofa/helper/AdvancedTimer.cpp
In file included from /home/one/Projects/sofa/src/SofaKernel/modules/SofaHelper/src/sofa/helper/AdvancedTimer.cpp:28:
In file included from /home/one/Projects/sofa/src/SofaKernel/extlibs/json/../../extlibs/json/json.h:5:
/home/one/Projects/sofa/src/SofaKernel/extlibs/json/nlohmann_json.h:12436:59: error: no type named 'string_view' in namespace 'std'
            and not std::is_same<ValueType, typename std::string_view>::value
                                            ~~~~~~~~~~~~~~^~~~~~~~~~~
1 error generated.

Upon some searching I came across topics which said that since string_view is available C++17 onwards. Is there an alternative version of clang that I should use for the compilation?

I am on Debian Stretch and am stuck with gcc-6.3

What would be my options to build Sofa successfully?

Regards,
Simit

[Simit]

I was able to fix this problem by including the necessary file as recommended in SO.

Here’s my patch that helped fix this problem. I am not sure if this is a hack or a legitimate fix.

diff --git a/SofaKernel/extlibs/json/nlohmann_json.h b/SofaKernel/extlibs/json/nlohmann_json.h                                    
index e02f62b146..c79ecabc62 100644                                                                                               
--- a/SofaKernel/extlibs/json/nlohmann_json.h                                                                                     
+++ b/SofaKernel/extlibs/json/nlohmann_json.h                                                                                     
@@ -54,6 +54,7 @@ SOFTWARE.                                                                                                       
 #include <memory> // allocator                                                                                                   
 #include <string> // string                                                                                                      
 #include <vector> // vector                                                                                                      
+#include <experimental/string_view>                                                                                              
                                                                                                                                  
 /*!                                                                                                                              
 @brief namespace for Niels Lohmann                                                                                               
@@ -12433,7 +12434,7 @@ namespace nlohmann                                                                                        
             and not std::is_same<ValueType, std::initializer_list<typename string_t::value_type>>::value                         
 #endif                                                                                                                           
 #if defined(JSON_HAS_CPP_17)                                                                                                     
-            and not std::is_same<ValueType, typename std::string_view>::value
+            and not std::is_same<ValueType, typename std::experimental::string_view>::value
 #endif
             , int >::type = 0 >
             operator ValueType() const

[Hugo]

Dear @psimit

Thank you so much for posting your issue AND your solution.
May I ask you to create a pull-request to propose this change back?

Then developers would discuss its integration.

Thanks again.
Best wishes!

Hugo

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