[cherry-pick] support python3.8 (#27450)

* Fix test_gast_with_compatibility.py due to the problem of gast in python3.8 (#27433)

test=develop

* fix dll load bug on windows from python3.8 (#27324)

* Support python3.8 (#26850)

* Support python3.8

test=notest

* Replace the 'spawn' start method with 'fork' start method for multiprocessing, on MacOS with python>=3.8 (#27317)

* Replace the 'spawn' start method with 'fork' start method for multiprocessing, on MacOs when python>=3.8

test=develop

* Correct the error in decorator.py (#27409)

test=develop
Co-authored-by: NZhou Wei <52485244+zhouwei25@users.noreply.github.com>

paddle/scripts/paddle_build.sh

@@ -121,6 +121,18 @@ function cmake_base() {
             else
                 exit 1
             fi
+        elif [ "$1" == "cp38-cp38" ]; then
+            if [ -d "/Library/Frameworks/Python.framework/Versions/3.8" ]; then
+                export LD_LIBRARY_PATH=/Library/Frameworks/Python.framework/Versions/3.8/lib/
+                export DYLD_LIBRARY_PATH=/Library/Frameworks/Python.framework/Versions/3.8/lib/
+                export PATH=/Library/Frameworks/Python.framework/Versions/3.8/bin/:${PATH}
+                PYTHON_FLAGS="-DPYTHON_EXECUTABLE:FILEPATH=/Library/Frameworks/Python.framework/Versions/3.8/bin/python3
+            -DPYTHON_INCLUDE_DIR:PATH=/Library/Frameworks/Python.framework/Versions/3.8/include/python3.8/
+            -DPYTHON_LIBRARY:FILEPATH=/Library/Frameworks/Python.framework/Versions/3.8/lib/libpython3.8.dylib"
+                pip3.8 install --user -r ${PADDLE_ROOT}/python/requirements.txt
+            else
+                exit 1
+            fi
         fi
         # delete `gym` to avoid modifying requirements.txt in *.whl
         sed -i .bak "/^gym$/d" ${PADDLE_ROOT}/python/requirements.txt
@@ -176,6 +188,13 @@ function cmake_base() {
             -DPYTHON_INCLUDE_DIR:PATH=/opt/_internal/cpython-3.7.0/include/python3.7m
             -DPYTHON_LIBRARIES:FILEPATH=/opt/_internal/cpython-3.7.0/lib/libpython3.so"
                 pip3.7 install -r ${PADDLE_ROOT}/python/requirements.txt
+            elif [ "$1" == "cp38-cp38" ]; then
+                export LD_LIBRARY_PATH=/opt/_internal/cpython-3.8.0/lib/:${LD_LIBRARY_PATH}
+                export PATH=/opt/_internal/cpython-3.8.0/bin/:${PATH}
+                export PYTHON_FLAGS="-DPYTHON_EXECUTABLE:FILEPATH=/opt/_internal/cpython-3.8.0/bin/python3.8
+            -DPYTHON_INCLUDE_DIR:PATH=/opt/_internal/cpython-3.8.0/include/python3.8
+            -DPYTHON_LIBRARIES:FILEPATH=/opt/_internal/cpython-3.8.0/lib/libpython3.so"
+                pip3.8 install -r ${PADDLE_ROOT}/python/requirements.txt
            fi
         else
             pip install -r ${PADDLE_ROOT}/python/requirements.txt
@@ -506,6 +525,8 @@ EOF
             pip3.6 uninstall -y paddlepaddle
         elif [ "$1" == "cp37-cp37m" ]; then
             pip3.7 uninstall -y paddlepaddle
+        elif [ "$1" == "cp38-cp38" ]; then
+            pip3.8 uninstall -y paddlepaddle
         fi
         set -ex
 
@@ -519,6 +540,8 @@ EOF
             pip3.6 install --user ${INSTALL_PREFIX:-/paddle/build}/opt/paddle/share/wheels/*.whl
         elif [ "$1" == "cp37-cp37m" ]; then
             pip3.7 install --user ${INSTALL_PREFIX:-/paddle/build}/opt/paddle/share/wheels/*.whl
+        elif [ "$1" == "cp38-cp38" ]; then
+            pip3.8 install --user ${INSTALL_PREFIX:-/paddle/build}/opt/paddle/share/wheels/*.whl
         fi
         ut_startTime_s=`date +%s`
         ctest --output-on-failure -j $2
@@ -592,7 +615,7 @@ function generate_api_spec() {
 
     awk -F '(' '{print $NF}' $spec_path >${spec_path}.doc
     awk -F '(' '{$NF="";print $0}' $spec_path >${spec_path}.api
-    if [ "$1" == "cp35-cp35m" ] || [ "$1" == "cp36-cp36m" ] || [ "$1" == "cp37-cp37m" ]; then 
+    if [ "$1" == "cp35-cp35m" ] || [ "$1" == "cp36-cp36m" ] || [ "$1" == "cp37-cp37m" ] || [ "$1" == "cp38-cp38" ]; then
         # Use sed to make python2 and python3 sepc keeps the same
         sed -i 's/arg0: str/arg0: unicode/g' $spec_path
         sed -i "s/\(.*Transpiler.*\).__init__ (ArgSpec(args=\['self'].*/\1.__init__ /g" $spec_path
@@ -1075,21 +1098,25 @@ EOF
     ref_paddle35=paddlepaddle${install_gpu}-${PADDLE_BRANCH}-cp35-cp35m-linux_x86_64.whl
     ref_paddle36=paddlepaddle${install_gpu}-${PADDLE_BRANCH}-cp36-cp36m-linux_x86_64.whl
     ref_paddle37=paddlepaddle${install_gpu}-${PADDLE_BRANCH}-cp37-cp37m-linux_x86_64.whl
+    ref_paddle38=paddlepaddle${install_gpu}-${PADDLE_BRANCH}-cp38-cp38-linux_x86_64.whl
 
     ref_paddle2_whl=paddlepaddle${install_gpu}-${PADDLE_BRANCH}-cp27-cp27mu-linux_x86_64.whl
     ref_paddle35_whl=paddlepaddle${install_gpu}-${PADDLE_BRANCH}-cp35-cp35m-linux_x86_64.whl
     ref_paddle36_whl=paddlepaddle${install_gpu}-${PADDLE_BRANCH}-cp36-cp36m-linux_x86_64.whl
     ref_paddle37_whl=paddlepaddle${install_gpu}-${PADDLE_BRANCH}-cp37-cp37m-linux_x86_64.whl
+    ref_paddle38_whl=paddlepaddle${install_gpu}-${PADDLE_BRANCH}-cp38-cp38-linux_x86_64.whl
 
     if [[ ${PADDLE_BRANCH} != "0.0.0" && ${WITH_MKL} == "ON" && ${WITH_GPU} == "ON" ]]; then
         ref_paddle2=paddlepaddle${install_gpu}-${PADDLE_BRANCH}.post${ref_CUDA_MAJOR}${CUDNN_MAJOR}-cp27-cp27mu-linux_x86_64.whl
         ref_paddle35=paddlepaddle${install_gpu}-${PADDLE_BRANCH}.post${ref_CUDA_MAJOR}${CUDNN_MAJOR}-cp35-cp35m-linux_x86_64.whl
         ref_paddle36=paddlepaddle${install_gpu}-${PADDLE_BRANCH}.post${ref_CUDA_MAJOR}${CUDNN_MAJOR}-cp36-cp36m-linux_x86_64.whl
         ref_paddle37=paddlepaddle${install_gpu}-${PADDLE_BRANCH}.post${ref_CUDA_MAJOR}${CUDNN_MAJOR}-cp37-cp37m-linux_x86_64.whl
+        ref_paddle38=paddlepaddle${install_gpu}-${PADDLE_BRANCH}.post${ref_CUDA_MAJOR}${CUDNN_MAJOR}-cp38-cp38-linux_x86_64.whl
         ref_paddle2_whl=paddlepaddle${install_gpu}-${PADDLE_BRANCH}.post${ref_CUDA_MAJOR}${CUDNN_MAJOR}-cp27-cp27mu-linux_x86_64.whl
         ref_paddle35_whl=paddlepaddle${install_gpu}-${PADDLE_BRANCH}.post${ref_CUDA_MAJOR}${CUDNN_MAJOR}-cp35-cp35m-linux_x86_64.whl
         ref_paddle36_whl=paddlepaddle${install_gpu}-${PADDLE_BRANCH}.post${ref_CUDA_MAJOR}${CUDNN_MAJOR}-cp36-cp36m-linux_x86_64.whl
         ref_paddle37_whl=paddlepaddle${install_gpu}-${PADDLE_BRANCH}.post${ref_CUDA_MAJOR}${CUDNN_MAJOR}-cp37-cp37m-linux_x86_64.whl
+        ref_paddle38_whl=paddlepaddle${install_gpu}-${PADDLE_BRANCH}.post${ref_CUDA_MAJOR}${CUDNN_MAJOR}-cp38-cp38-linux_x86_64.whl
     fi
 
     #ref_paddle2_mv1=""
@@ -1194,6 +1221,22 @@ EOF
         apt-get clean -y && \
         rm -f ${ref_paddle37} && \
         ldconfig
+EOF
+    cat >> ${PADDLE_ROOT}/build/Dockerfile <<EOF
+    # run paddle version to install python packages first
+    RUN apt-get update && ${NCCL_DEPS}
+    RUN apt-get install -y make build-essential libssl-dev zlib1g-dev libbz2-dev \
+        libreadline-dev libsqlite3-dev wget curl llvm libncurses5-dev libncursesw5-dev \
+        xz-utils tk-dev libffi-dev liblzma-dev
+    RUN wget -q https://www.python.org/ftp/python/3.8.0/Python-3.8.0.tgz && \
+        tar -xzf Python-3.8.0.tgz && cd Python-3.8.0 && \
+        CFLAGS="-Wformat" ./configure --prefix=/usr/local/ --enable-shared > /dev/null && \
+        make -j8 > /dev/null && make altinstall > /dev/null && cd ../ && rm Python-3.8.0.tgz
+    RUN apt-get install -y libgtk2.0-dev dmidecode python3-tk && ldconfig && \
+        pip3.8 install opencv-python && wget ${ref_web}/${ref_paddle38} && pip3.8 install ${ref_paddle38_whl}; apt-get install -f -y && \
+        apt-get clean -y && \
+        rm -f ${ref_paddle38} && \
+        ldconfig
 EOF
     cat >> ${PADDLE_ROOT}/build/Dockerfile <<EOF
     # run paddle version to install python packages first

python/paddle/fluid/core.py

@@ -39,6 +39,11 @@ try:
         third_lib_path = current_path + os.sep + '..' + os.sep + 'libs'
         os.environ['path'] = third_lib_path + ';' + os.environ['path']
         sys.path.insert(0, third_lib_path)
+        # Note: from python3.8, PATH will not take effect
+        # https://github.com/python/cpython/pull/12302
+        # Use add_dll_directory to specify dll resolution path
+        if sys.version_info[:2] >= (3, 8):
+            os.add_dll_directory(third_lib_path)
 
 except ImportError as e:
     from .. import compat as cpt

python/paddle/fluid/tests/unittests/test_gast_with_compatibility.py

@@ -16,6 +16,7 @@ from __future__ import print_function
 
 import ast
 import gast
+import sys
 import textwrap
 import unittest
 
@@ -143,6 +144,19 @@ class TestPythonCompatibility(unittest.TestCase):
         """
         self._check_compatibility(source, target)
 
+    # The 0.3.3 version of gast has a bug in python3.8 that
+    # would cause the following tests to fail. But this 
+    # problem doesn't affect the use of Paddle's related 
+    # functions, therefore, the following tests would be 
+    # disable in python3.8.
+    #
+    # This problem had been fixed and updated to version 
+    # 0.4.1 of gast.
+    #
+    # More information please refer to:
+    # https://github.com/serge-sans-paille/gast/issues/49
+    if sys.version_info < (3, 8):
+
         def test_with(self):
             """
             The fileds `context_expr/optional_vars` of `ast.With` in PY2

python/paddle/reader/decorator.py

@@ -32,6 +32,21 @@ import random
 import zlib
 import paddle.compat as cpt
 
+# On macOS, the 'spawn' start method is now the default in Python3.8 multiprocessing,
+# Paddle is currently unable to solve this, so forces the process to start using 
+# the 'fork' start method.
+#
+# TODO: This solution is not good, because the fork start method could lead to 
+# crashes of the subprocess. Figure out how to make 'spawn' work.
+#
+# For more details, please refer to
+# https://docs.python.org/3/library/multiprocessing.html#contexts-and-start-methods
+# https://bugs.python.org/issue33725
+if sys.version_info >= (3, 8) and sys.platform == 'darwin':
+    fork_context = multiprocessing.get_context('fork')
+else:
+    fork_context = multiprocessing
+
 
 def cache(reader):
     """
@@ -556,9 +571,9 @@ def multiprocess_reader(readers, use_pipe=True, queue_size=1000):
             six.reraise(*sys.exc_info())
 
     def queue_reader():
-        queue = multiprocessing.Queue(queue_size)
+        queue = fork_context.Queue(queue_size)
         for reader in readers:
-            p = multiprocessing.Process(
+            p = fork_context.Process(
                 target=_read_into_queue, args=(reader, queue))
             p.start()
 
@@ -589,9 +604,9 @@ def multiprocess_reader(readers, use_pipe=True, queue_size=1000):
     def pipe_reader():
         conns = []
         for reader in readers:
-            parent_conn, child_conn = multiprocessing.Pipe()
+            parent_conn, child_conn = fork_context.Pipe()
             conns.append(parent_conn)
-            p = multiprocessing.Process(
+            p = fork_context.Process(
                 target=_read_into_pipe, args=(reader, child_conn))
             p.start()