pip install fails on AIX

[shubhamhii]

Pip install is failing on AIX due to undefined symbol.
Log:

building '_cffi_backend' extension
creating build/temp.aix-7105-9988-64-cpython-39
creating build/temp.aix-7105-9988-64-cpython-39/src
creating build/temp.aix-7105-9988-64-cpython-39/src/c
gcc -Wno-unused-result -Wsign-compare -DNDEBUG -g -O2 -Wall -I/opt/freeware/include -I/usr/include -DAIX_GENUINE_CPLUSCPLUS -D_ALL_SOURCE -D_LINUX_SOURCE_COMPAT -I/opt/freeware/include -I/usr/include -DAIX_GENUINE_CPLUSCPLUS -D_ALL_SOURCE -D_LINUX_SOURCE_COMPAT -maix64 -I/usr/local/include -I/opt/freeware/include -DFFI_BUILDING=1 -DUSE__THREAD -I/opt/freeware/include -I/opt/freeware/include/python3.9 -c src/c/_cffi_backend.c -o build/temp.aix-7105-9988-64-cpython-39/src/c/_cffi_backend.o
src/c/_cffi_backend.c: In function 'cdata_call':
src/c/_cffi_backend.c:3240:30: warning: comparison of integer expressions of different signedness: 'Py_ssize_t' {aka 'long int'} and 'long unsigned int' [-Wsign-compare]
 3240 |         if (fresult->ct_size < sizeof(ffi_arg))
      |                              ^
In file included from src/c/cffi1_module.c:20,
                 from src/c/_cffi_backend.c:8027:
src/c/call_python.c: In function 'cffi_call_python':
src/c/call_python.c:203:28: warning: implicit declaration of function '__lwsync' [-Wimplicit-function-declaration]
  203 | #   define read_barrier()  __lwsync()
      |                            ^~~~~~~~
src/c/call_python.c:252:5: note: in expansion of macro 'read_barrier'
  252 |     read_barrier();
      |     ^~~~~~~~~~~~
/opt/freeware/lib64/python3.9/config-3.9/ld_so_aix gcc -maix64 -fPIC -pthread -O2 -bI:/opt/freeware/lib64/python3.9/config-3.9/python.exp -L/opt/freeware/lib/pthread -L/opt/freeware/lib64 -L/opt/freeware/lib -L/usr/lib -Wl,-blibpath:/opt/freeware/lib/pthread:/opt/freeware/lib64:/opt/freeware/lib:/usr/lib -L/opt/freeware/lib/pthread -L/opt/freeware/lib64 -L/opt/freeware/lib -L/usr/lib -Wl,-blibpath:/opt/freeware/lib/pthread:/opt/freeware/lib64:/opt/freeware/lib:/usr/lib -L/opt/freeware/lib64 -L/opt/freeware/lib -lgcc -maix64 -I/usr/local/include -I/opt/freeware/include build/temp.aix-7105-9988-64-cpython-39/src/c/_cffi_backend.o -L/opt/freeware/lib64 -L/opt/freeware/lib64 -lffi -o build/lib.aix-7105-9988-64-cpython-39/_cffi_backend.cpython-39.so
ld: 0711-317 ERROR: Undefined symbol: .__lwsync

[arigo]

This function comes from a block a few lines above that was copied from somewhere long ago:

...
# if defined(HAVE_SYNC_SYNCHRONIZE)
#   define read_barrier()  __sync_synchronize()
# elif defined(_AIX)
#   define read_barrier()  __lwsync()
...

Apparently you're using a C compiler (is that really gcc?) that for some reason doesn't have either __sync_synchronize() nor __lwsync(). Or maybe it does have __sync_synchronize() but the HAVE_SYNC_SYNCHRONIZE is not defined for some reason?

[shubhamhii]

Hi,

Thanks for the suggestion. By including HAVE_SYNC_SYNCHRONIZE in CFLAGS we are able to build with pip.
However, we are able to build without setting explicitly HAVE_SYNC_SYNCHRONIZE in setup.py build.

Regards,
Shubham