nix-build failing whereas nix-shell --pure works

[sbellem]

Building and installing the SGX SDK works in a nix-shell session, including when using the --pure option, but when building with nix-build it fails as it tries to apply an OpenMP patch with git, which is not available.

Thing to look for:

• Is git available in the nix shell session?
• Find out if the patch is applied in nix shell session.
• Understand differences between using nix-build, nix-shell and nix-shell --pure. Why is --pure not "pure enough"?
• If patch is not applied in nix shell session, then just disable the trigger for when using nix-build. But try to understand what is causing the different behaviors.
• temporary measure: try adding git as a dependency

For use an already patched version of openmp and disable the check and git apply command invocation.

make[3]: Leaving directory '/tmp/nix-build-sgx.drv-0/source/sdk/pthread'
make -C /tmp/nix-build-sgx.drv-0/source/external/openmp
make[3]: Entering directory '/tmp/nix-build-sgx.drv-0/source/external/openmp'
cd openmp_code && git apply ../0001-Enable-OpenMP-in-SGX.patch && cd ..
/nix/store/l6h4ya0wzb4b8mr0y58k2gh2nhfql4sn-bash-4.4-p23/bin/bash: git: command not found
make[3]: *** [Makefile:70: openmp_code/final/build/runtime/src/libomp.a] Error 127
make[3]: Leaving directory '/tmp/nix-build-sgx.drv-0/source/external/openmp'
make[2]: *** [Makefile.source:201: openmp] Error 2
make[2]: Leaving directory '/tmp/nix-build-sgx.drv-0/source/sdk'
make[1]: *** [Makefile:50: all] Error 2
make[1]: Leaving directory '/tmp/nix-build-sgx.drv-0/source/sdk'
make: *** [Makefile:70: sdk] Error 2
builder for '/nix/store/vmwr9980q11idzyzzpbqhwfjapkf3zsv-sgx.drv' failed with exit code 2
error: build of '/nix/store/vmwr9980q11idzyzzpbqhwfjapkf3zsv-sgx.drv' failed

[sbellem]

https://nixos.wiki/wiki/Development_environment_with_nix-shell

[sbellem]

when using already patched openmp:

make[6]: Leaving directory '/tmp/nix-build-sgx.drv-0/source/external/openmp/openmp_code/final/build'
[  5%] Built target libomp-needed-headers
make[6]: Entering directory '/tmp/nix-build-sgx.drv-0/source/external/openmp/openmp_code/final/build'
Scanning dependencies of target omp
make[6]: Leaving directory '/tmp/nix-build-sgx.drv-0/source/external/openmp/openmp_code/final/build'
make[6]: Entering directory '/tmp/nix-build-sgx.drv-0/source/external/openmp/openmp_code/final/build'
[  8%] Building C object runtime/src/CMakeFiles/omp.dir/thirdparty/ittnotify/ittnotify_static.c.o
[ 11%] Building CXX object runtime/src/CMakeFiles/omp.dir/kmp_alloc.cpp.o
In file included from /tmp/nix-build-sgx.drv-0/source/external/openmp/openmp_code/final/runtime/src/kmp.h:62,
                 from /tmp/nix-build-sgx.drv-0/source/external/openmp/openmp_code/final/runtime/src/kmp_alloc.cpp:14:
/nix/store/7b67hqgxavm47qizrkya55qvyp1f65s4-glibc-2.27-dev/include/signal.h:301:11: fatal error: stddef.h: No such file or directory
 # include <stddef.h>
           ^~~~~~~~~~
compilation terminated.
make[6]: *** [runtime/src/CMakeFiles/omp.dir/build.make:76: runtime/src/CMakeFiles/omp.dir/kmp_alloc.cpp.o] Error 1
make[6]: Leaving directory '/tmp/nix-build-sgx.drv-0/source/external/openmp/openmp_code/final/build'
make[5]: *** [CMakeFiles/Makefile2:234: runtime/src/CMakeFiles/omp.dir/all] Error 2
make[5]: Leaving directory '/tmp/nix-build-sgx.drv-0/source/external/openmp/openmp_code/final/build'
make[4]: *** [Makefile:130: all] Error 2
make[4]: Leaving directory '/tmp/nix-build-sgx.drv-0/source/external/openmp/openmp_code/final/build'
make[3]: *** [Makefile:73: openmp_code/final/build/runtime/src/libomp.a] Error 2
make[3]: Leaving directory '/tmp/nix-build-sgx.drv-0/source/external/openmp'
make[2]: *** [Makefile.source:201: openmp] Error 2
make[2]: Leaving directory '/tmp/nix-build-sgx.drv-0/source/sdk'
make[1]: *** [Makefile:50: all] Error 2
make[1]: Leaving directory '/tmp/nix-build-sgx.drv-0/source/sdk'
make: *** [Makefile:70: sdk] Error 2
builder for '/nix/store/0640jh4gs8fm1x16hfps5dss3mpc7nja-sgx.drv' failed with exit code 2
error: build of '/nix/store/0640jh4gs8fm1x16hfps5dss3mpc7nja-sgx.drv' failed

[sbellem]

In the nix shell, the patch is applied:

make[3]: Leaving directory '/usr/src/source/sdk/pthread'                                                                                                                                                 [146/32369]
make -C /usr/src/source/external/openmp
make[3]: Entering directory '/usr/src/source/external/openmp'
cd openmp_code && git apply ../0001-Enable-OpenMP-in-SGX.patch && cd ..
../0001-Enable-OpenMP-in-SGX.patch:239: trailing whitespace.
#define KMP_NOW() get_timestamp()
../0001-Enable-OpenMP-in-SGX.patch:341: trailing whitespace.
#ifndef _OPENMP_SGX
../0001-Enable-OpenMP-in-SGX.patch:748: trailing whitespace.
#ifdef _OPENMP_SGX
../0001-Enable-OpenMP-in-SGX.patch:1043: trailing whitespace.
        return __sync_add_and_fetch(&__kmp_global_count, 20*KMP_USEC_PER_SEC);
../0001-Enable-OpenMP-in-SGX.patch:1123: trailing whitespace.
#endif // _OPENMP_SGX
warning: squelched 3 whitespace errors
warning: 8 lines add whitespace errors.
mkdir -p openmp_code/final/build && cd openmp_code/final/build && cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_C_COMPILER_WORKS=TRUE -DCMAKE_CXX_COMPILER_WORKS=TRUE -DCMAKE_CXX_FLAGS=" -ffreestanding -nostdinc -fvisi
bility=hidden  -fpic -fno-strict-overflow -fno-delete-null-pointer-checks -B/usr/src/source/external/toolset/nix -mindirect-branch-register -fcf-protection=none -mfunction-return=thunk-extern -fno-plt -Wa,-mlfenc
e-after-load=yes -Wa,-mlfence-before-indirect-branch=memory -Wa,-mlfence-before-ret=shl -nostdinc++" .. && make
-- The C compiler identification is GNU 8.3.0
-- The CXX compiler identification is GNU 8.3.0
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - failed
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Performing Test OPENMP_HAVE_WERROR_FLAG
-- Performing Test OPENMP_HAVE_WERROR_FLAG - Success
-- Performing Test OPENMP_HAVE_STD_GNUPP11_FLAG
-- Performing Test OPENMP_HAVE_STD_GNUPP11_FLAG - Failed
-- Performing Test OPENMP_HAVE_STD_CPP11_FLAG
-- Performing Test OPENMP_HAVE_STD_CPP11_FLAG - Failed
-- Found PythonInterp: /nix/store/k0igqpz995nmxwf6piyd5jjpcc7gcnyc-python3-3.7.4/bin/python (found version "3.7.4")
-- Cannot find llvm-lit.
-- Please put llvm-lit in your PATH, set OPENMP_LLVM_LIT_EXECUTABLE to its full path, or point OPENMP_LLVM_TOOLS_DIR to its directory.
CMake Warning at cmake/OpenMPTesting.cmake:22 (message):
  The check targets will not be available!
Call Stack (most recent call first):
  cmake/OpenMPTesting.cmake:40 (find_standalone_test_dependencies)
  CMakeLists.txt:49 (include)
...