3 files changed, 103 insertions, 2 deletions
diff --git a/Lib/_aix_support.py b/Lib/_aix_support.py
new file mode 100644
index 0000000..2c5cd32
--- /dev/null
+++ b/Lib/_aix_support.py
@@ -0,0 +1,99 @@
+"""Shared AIX support functions."""
+
+import sys
+from sysconfig import get_config_var
+
+# subprocess is not necessarily available early in the build process
+# if not available, the config_vars are also definitely not available
+# supply substitutes to bootstrap the build
+try:
+    import subprocess
+    _have_subprocess = True
+    _tmp_bd = get_config_var("AIX_BUILDDATE")
+    _bgt = get_config_var("BUILD_GNU_TYPE")
+except ImportError:  # pragma: no cover
+    _have_subprocess = False
+    _tmp_bd = None
+    _bgt = "powerpc-ibm-aix6.1.7.0"
+
+# if get_config_var("AIX_BUILDDATE") was unknown, provide a substitute,
+# impossible builddate to specify 'unknown'
+_MISSING_BD = 9898
+try:
+    _bd = int(_tmp_bd)
+except TypeError:
+    _bd = _MISSING_BD
+
+# Infer the ABI bitwidth from maxsize (assuming 64 bit as the default)
+_sz = 32 if sys.maxsize == (2**31-1) else 64
+
+
+def _aix_tag(vrtl, bd):
+    # type: (List[int], int) -> str
+    # vrtl[version, release, technology_level]
+    return "aix-{:1x}{:1d}{:02d}-{:04d}-{}".format(vrtl[0], vrtl[1], vrtl[2], bd, _sz)
+
+
+# extract version, release and technology level from a VRMF string
+def _aix_vrtl(vrmf):
+    # type: (str) -> List[int]
+    v, r, tl = vrmf.split(".")[:3]
+    return [int(v[-1]), int(r), int(tl)]
+
+
+def _aix_bosmp64():
+    # type: () -> Tuple[str, int]
+    """
+    Return a Tuple[str, int] e.g., ['7.1.4.34', 1806]
+    The fileset bos.mp64 is the AIX kernel. It's VRMF and builddate
+    reflect the current ABI levels of the runtime environment.
+    """
+    if _have_subprocess:
+        # We expect all AIX systems to have lslpp installed in this location
+        out = subprocess.check_output(["/usr/bin/lslpp", "-Lqc", "bos.mp64"])
+        out = out.decode("utf-8").strip().split(":")  # type: ignore
+        # Use str() and int() to help mypy see types
+        return str(out[2]), int(out[-1])
+    else:
+        from os import uname
+
+        osname, host, release, version, machine = uname()
+        return "{}.{}.0.0".format(version, release), _MISSING_BD
+
+
+def aix_platform():
+    # type: () -> str
+    """
+    AIX filesets are identified by four decimal values: V.R.M.F.
+    V (version) and R (release) can be retreived using ``uname``
+    Since 2007, starting with AIX 5.3 TL7, the M value has been
+    included with the fileset bos.mp64 and represents the Technology
+    Level (TL) of AIX. The F (Fix) value also increases, but is not
+    relevant for comparing releases and binary compatibility.
+    For binary compatibility the so-called builddate is needed.
+    Again, the builddate of an AIX release is associated with bos.mp64.
+    AIX ABI compatibility is described  as guaranteed at: https://www.ibm.com/\
+    support/knowledgecenter/en/ssw_aix_72/install/binary_compatability.html
+
+    For pep425 purposes the AIX platform tag becomes:
+    "aix-{:1x}{:1d}{:02d}-{:04d}-{}".format(v, r, tl, builddate, bitsize)
+    e.g., "aix-6107-1415-32" for AIX 6.1 TL7 bd 1415, 32-bit
+    and, "aix-6107-1415-64" for AIX 6.1 TL7 bd 1415, 64-bit
+    """
+    vrmf, bd = _aix_bosmp64()
+    return _aix_tag(_aix_vrtl(vrmf), bd)
+
+
+# extract vrtl from the BUILD_GNU_TYPE as an int
+def _aix_bgt():
+    # type: () -> List[int]
+    assert _bgt
+    return _aix_vrtl(vrmf=_bgt)
+
+
+def aix_buildtag():
+    # type: () -> str
+    """
+    Return the platform_tag of the system Python was built on.
+    """
+    return _aix_tag(_aix_bgt(), _bd)
diff --git a/Lib/distutils/util.py b/Lib/distutils/util.py
index 17a94bc..4b002ec 100644
--- a/Lib/distutils/util.py
+++ b/Lib/distutils/util.py
@@ -79,7 +79,8 @@ def get_host_platform():
             machine += ".%s" % bitness[sys.maxsize]
         # fall through to standard osname-release-machine representation
     elif osname[:3] == "aix":
-        return "%s-%s.%s" % (osname, version, release)
+        from _aix_support import aix_platform
+        return aix_platform()
     elif osname[:6] == "cygwin":
         osname = "cygwin"
         rel_re = re.compile (r'[\d.]+', re.ASCII)
diff --git a/Lib/sysconfig.py b/Lib/sysconfig.py
index b9e2faf..64cf156 100644
--- a/Lib/sysconfig.py
+++ b/Lib/sysconfig.py
@@ -665,7 +665,8 @@ def get_platform():
             machine += ".%s" % bitness[sys.maxsize]
         # fall through to standard osname-release-machine representation
     elif osname[:3] == "aix":
-        return "%s-%s.%s" % (osname, version, release)
+        from _aix_support import aix_platform
+        return aix_platform()
     elif osname[:6] == "cygwin":
         osname = "cygwin"
         import re