scons: Test if binaries can embed the Python interpreter

Add some more stringent Python tests that ensure that we can link with
and run applications that embed Python. This is implemented by running
building a small c++ program that embeds Python using PyBind11. The
program is run by the build system and prints the version of the
Python interpreter. The version information is then used by the build
system to ensure that the installed version is supported.

Change-Id: I727e0832f171362f5506247c022bea365068a0f6
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/36383
Reviewed-by: Gabe Black <gabe.black@gmail.com>
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

diff --git a/SConstruct b/SConstruct
index 8e7ec3481ec138eeff17b86f91ecce4e466c6a4d..a057da3083565a3628b5e79d7406db5055a3f039 100755 (executable)
--- a/SConstruct
+++ b/SConstruct
@@ -575,6 +575,27 @@ int main(){
     context.Result(ret)
     return ret
 
+def CheckPythonLib(context):
+    context.Message('Checking Python version... ')
+    ret = context.TryRun(r"""
+#include <pybind11/embed.h>
+
+int
+main(int argc, char **argv) {
+    pybind11::scoped_interpreter guard{};
+    pybind11::exec(
+        "import sys\n"
+        "vi = sys.version_info\n"
+        "sys.stdout.write('%i.%i.%i' % (vi.major, vi.minor, vi.micro));\n");
+    return 0;
+}
+    """, extension=".cc")
+    context.Result(ret[1] if ret[0] == 1 else 0)
+    if ret[0] == 0:
+        return None
+    else:
+        return tuple(map(int, ret[1].split(".")))
+
 # Platform-specific configuration.  Note again that we assume that all
 # builds under a given build root run on the same host platform.
 conf = Configure(main,
@@ -582,6 +603,7 @@ conf = Configure(main,
                  log_file = joinpath(build_root, 'scons_config.log'),
                  custom_tests = {
         'CheckMember' : CheckMember,
+        'CheckPythonLib' : CheckPythonLib,
         })
 
 # Check if we should compile a 64 bit binary on Mac OS X/Darwin
@@ -637,9 +659,6 @@ if main['USE_PYTHON']:
               main['PYTHON_CONFIG'])
 
     print("Info: Using Python config: %s" % (python_config, ))
-    if python_config != 'python3-config':
-        warning('python3-config could not be found.\n'
-                'Future releases of gem5 will drop support for python2.')
 
     py_includes = readCommand([python_config, '--includes'],
                               exception='').split()
@@ -697,6 +716,17 @@ main.Prepend(CPPPATH=Dir('ext/pybind11/include/'))
 marshal_env = main.Clone()
 marshal_env.Append(CCFLAGS='$MARSHAL_CCFLAGS_EXTRA')
 marshal_env.Append(LINKFLAGS='$MARSHAL_LDFLAGS_EXTRA')
+py_version = conf.CheckPythonLib()
+if not py_version:
+    error("Can't find a working Python installation")
+
+# Found a working Python installation. Check if it meets minimum
+# requirements.
+if py_version[0] < 3 or \
+   (py_version[0] == 3 and py_version[1] < 6):
+    error('Python version too old. Version 3.6 or newer is required.')
+elif py_version[0] > 3:
+    warning('Python version too new. Python 3 expected.')
 
 # On Solaris you need to use libsocket for socket ops
 if not conf.CheckLibWithHeader(None, 'sys/socket.h', 'C++', 'accept(0,0,0);'):