How to compile this as a shared library ?

[abhi18av]

Hi everyone,

I was wondering if you could please tell how I could compile this as a shared library ?

I tried using cmake but so far, without any success. Please point me to a better direction

[gchatelet]

You compile shared library by specifying the flag on the cmake command line:

 % cmake -DCMAKE_BUILD_TYPE=Release -DBUILD_SHARED_LIBS=ON -H. -Bcmake_build
 % cd cmake_build
 % make
Scanning dependencies of target cpu_features
[  6%] Building C object CMakeFiles/cpu_features.dir/src/linux_features_aggregator.c.o
[ 13%] Building C object CMakeFiles/cpu_features.dir/src/cpuid_x86_clang_gcc.c.o
[ 20%] Building C object CMakeFiles/cpu_features.dir/src/cpuid_x86_msvc.c.o
[ 26%] Building C object CMakeFiles/cpu_features.dir/src/cpuinfo_aarch64.c.o
[ 33%] Building C object CMakeFiles/cpu_features.dir/src/cpuinfo_arm.c.o
[ 40%] Building C object CMakeFiles/cpu_features.dir/src/cpuinfo_mips.c.o
[ 46%] Building C object CMakeFiles/cpu_features.dir/src/cpuinfo_ppc.c.o
[ 53%] Building C object CMakeFiles/cpu_features.dir/src/cpuinfo_x86.c.o
[ 60%] Building C object CMakeFiles/cpu_features.dir/src/filesystem.c.o
[ 66%] Building C object CMakeFiles/cpu_features.dir/src/hwcaps.c.o
[ 73%] Building C object CMakeFiles/cpu_features.dir/src/stack_line_reader.c.o
[ 80%] Building C object CMakeFiles/cpu_features.dir/src/string_view.c.o
[ 86%] Linking C shared library libcpu_features.so
[ 86%] Built target cpu_features
Scanning dependencies of target list_cpu_features
[ 93%] Building C object CMakeFiles/list_cpu_features.dir/src/utils/list_cpu_features.c.o
[100%] Linking C executable list_cpu_features
[100%] Built target list_cpu_features

Please note that the use of shared libraries for cpu_features is discouraged as stated here.

[abhi18av]

Oh, I see !

Thanks a lot @gchatelet 👍

[abhi18av]

@gchatelet , I ran into an error while running this command on the macOS system

Abhinavs-MacBook-Pro:cpu_features eklavya$ cmake -DCMAKE_BUILD_TYPE=Release -DBUILD_SHARED_LIBS=ON -H. -Bcmake_build
-- The C compiler identification is AppleClang 9.1.0.9020039
-- The CXX compiler identification is AppleClang 9.1.0.9020039
-- Check for working C compiler: /Library/Developer/CommandLineTools/usr/bin/cc
-- Check for working C compiler: /Library/Developer/CommandLineTools/usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /Library/Developer/CommandLineTools/usr/bin/c++
-- Check for working CXX compiler: /Library/Developer/CommandLineTools/usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Configuring done
-- Generating done
-- Build files have been written to: /Users/eklavya/projects/code/c-shared-lab/cpu_features/cmake_build


Abhinavs-MacBook-Pro:cpu_features eklavya$ cd cmake_build/


Abhinavs-MacBook-Pro:cmake_build eklavya$ make 
Scanning dependencies of target cpu_features
[  6%] Building C object CMakeFiles/cpu_features.dir/src/linux_features_aggregator.c.o
[ 13%] Building C object CMakeFiles/cpu_features.dir/src/cpuid_x86_clang_gcc.c.o
[ 20%] Building C object CMakeFiles/cpu_features.dir/src/cpuid_x86_msvc.c.o
[ 26%] Building C object CMakeFiles/cpu_features.dir/src/cpuinfo_aarch64.c.o
[ 33%] Building C object CMakeFiles/cpu_features.dir/src/cpuinfo_arm.c.o
[ 40%] Building C object CMakeFiles/cpu_features.dir/src/cpuinfo_mips.c.o
[ 46%] Building C object CMakeFiles/cpu_features.dir/src/cpuinfo_ppc.c.o
[ 53%] Building C object CMakeFiles/cpu_features.dir/src/cpuinfo_x86.c.o
[ 60%] Building C object CMakeFiles/cpu_features.dir/src/filesystem.c.o
[ 66%] Building C object CMakeFiles/cpu_features.dir/src/hwcaps.c.o
[ 73%] Building C object CMakeFiles/cpu_features.dir/src/stack_line_reader.c.o
[ 80%] Building C object CMakeFiles/cpu_features.dir/src/string_view.c.o
[ 86%] Linking C shared library libcpu_features.dylib
Undefined symbols for architecture x86_64:
  "_CpuFeatures_GetPlatformType", referenced from:
      _GetPPCPlatformStrings in cpuinfo_ppc.c.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make[2]: *** [libcpu_features.dylib] Error 1
make[1]: *** [CMakeFiles/cpu_features.dir/all] Error 2
make: *** [all] Error 2

[abhi18av]

Shall I report this separately ?

[abhi18av]

Hmm, I tried it on my bare-metal ARMv7 - C1 instance on scaleaway and it failed to compile again

root@tuffy:~/projects/code/c-shared-libs# cd cpu_features/
root@tuffy:~/projects/code/c-shared-libs/cpu_features# cmake -DCMAKE_BUILD_TYPE=Release -DBUILD_SHARED_LIBS=ON -H. -Bcmake_build
-- The C compiler identification is GNU 7.3.0
-- The CXX compiler identification is GNU 7.3.0
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Configuring done
-- Generating done
-- Build files have been written to: /root/projects/code/c-shared-libs/cpu_features/cmake_build
root@tuffy:~/projects/code/c-shared-libs/cpu_features# cd cmake_build/
root@tuffy:~/projects/code/c-shared-libs/cpu_features/cmake_build# make
Scanning dependencies of target cpu_features
[  6%] Building C object CMakeFiles/cpu_features.dir/src/linux_features_aggregator.c.o
[ 13%] Building C object CMakeFiles/cpu_features.dir/src/cpuid_x86_clang_gcc.c.o
[ 20%] Building C object CMakeFiles/cpu_features.dir/src/cpuid_x86_msvc.c.o
[ 26%] Building C object CMakeFiles/cpu_features.dir/src/cpuinfo_aarch64.c.o
[ 33%] Building C object CMakeFiles/cpu_features.dir/src/cpuinfo_arm.c.o
[ 40%] Building C object CMakeFiles/cpu_features.dir/src/cpuinfo_mips.c.o
[ 46%] Building C object CMakeFiles/cpu_features.dir/src/cpuinfo_ppc.c.o
[ 53%] Building C object CMakeFiles/cpu_features.dir/src/cpuinfo_x86.c.o
[ 60%] Building C object CMakeFiles/cpu_features.dir/src/filesystem.c.o
[ 66%] Building C object CMakeFiles/cpu_features.dir/src/hwcaps.c.o
[ 73%] Building C object CMakeFiles/cpu_features.dir/src/stack_line_reader.c.o
[ 80%] Building C object CMakeFiles/cpu_features.dir/src/string_view.c.o
[ 86%] Linking C shared library libcpu_features.so
[ 86%] Built target cpu_features
Scanning dependencies of target list_cpu_features
[ 93%] Building C object CMakeFiles/list_cpu_features.dir/src/utils/list_cpu_features.c.o
[100%] Linking C executable list_cpu_features
libcpu_features.so: undefined reference to `GetXCR0Eax'
libcpu_features.so: undefined reference to `CpuId'
collect2: error: ld returned 1 exit status
CMakeFiles/list_cpu_features.dir/build.make:95: recipe for target 'list_cpu_features' failed
make[2]: *** [list_cpu_features] Error 1
CMakeFiles/Makefile2:67: recipe for target 'CMakeFiles/list_cpu_features.dir/all' failed
make[1]: *** [CMakeFiles/list_cpu_features.dir/all] Error 2
Makefile:129: recipe for target 'all' failed
make: *** [all] Error 2

Am I doing something wrong here ?

[gchatelet]

@abhi18av Please create a separate issue for both of them.

[abhi18av]

Yup, done 👍