Merge branch 'master' into smart_holder

README.rst

@@ -18,20 +18,6 @@
    This is the pybind11 **smart_holder** branch. Please refer to
    ``README_smart_holder.rst`` for branch-specific information.
 
-.. warning::
-
-   Combining older versions of pybind11 (< 2.6.0) with Python 3.9.0 will
-   trigger undefined behavior that typically manifests as crashes during
-   interpreter shutdown (but could also destroy your data. **You have been
-   warned.**)
-
-   We recommend that you update to the latest patch release of Python (3.9.1),
-   which includes a `fix <https://github.com/python/cpython/pull/22670>`_
-   that resolves this problem. If you do use Python 3.9.0, please update to
-   the latest version of pybind11 (2.6.0 or newer), which includes a temporary
-   workaround specifically when Python 3.9.0 is detected at runtime.
-
-
 **pybind11** is a lightweight header-only library that exposes C++ types
 in Python and vice versa, mainly to create Python bindings of existing
 C++ code. Its goals and syntax are similar to the excellent
@@ -115,7 +101,7 @@ goodies:
   transparently applied to all entries of one or more NumPy array
   arguments.
 
-- Python’s slice-based access and assignment operations can be
+- Python's slice-based access and assignment operations can be
   supported with just a few lines of code.
 
 - Everything is contained in just a few header files; there is no need

docs/limitations.rst

@@ -57,16 +57,16 @@ clean, well written patch would likely be accepted to solve them.
 Python 3.9.0 warning
 ^^^^^^^^^^^^^^^^^^^^
 
-Combining older versions of pybind11 (< 2.6.0) with Python on 3.9.0 will
-trigger undefined behavior that typically manifests as crashes during
+Combining older versions of pybind11 (< 2.6.0) with Python on exactly 3.9.0
+will trigger undefined behavior that typically manifests as crashes during
 interpreter shutdown (but could also destroy your data. **You have been
 warned**).
 
-This issue has been
-`fixed in Python <https://github.com/python/cpython/pull/22670>`_.  As a
-mitigation until 3.9.1 is released and commonly used, pybind11 (2.6.0 or newer)
-includes a temporary workaround specifically when Python 3.9.0 is detected at
-runtime, leaking about 50 bytes of memory when a callback function is garbage
-collected. For reference; the pybind11 test suite has about 2,000 such
-callbacks, but only 49 are garbage collected before the end-of-process. Wheels
-built with Python 3.9.0 will correctly avoid the leak when run in Python 3.9.1.
+This issue was `fixed in Python <https://github.com/python/cpython/pull/22670>`_.
+As a mitigation for this bug, pybind11 2.6.0 or newer includes a workaround
+specifically when Python 3.9.0 is detected at runtime, leaking about 50 bytes
+of memory when a callback function is garbage collected.  For reference, the
+pybind11 test suite has about 2,000 such callbacks, but only 49 are garbage
+collected before the end-of-process. Wheels (even if built with Python 3.9.0)
+will correctly avoid the leak when run in Python 3.9.1, and this does not
+affect other 3.X versions.

docs/requirements.txt

@@ -1,4 +1,7 @@
 breathe==4.26.1
+# docutils 0.17 breaks HTML tags & RTD theme
+# https://github.com/sphinx-doc/sphinx/issues/9001
+docutils==0.16
 sphinx==3.3.1
 sphinx_rtd_theme==0.5.0
 sphinxcontrib-moderncmakedomain==3.17

include/pybind11/detail/common.h

@@ -13,6 +13,10 @@
 #define PYBIND11_VERSION_MINOR 6
 #define PYBIND11_VERSION_PATCH 3.dev1
 
+// Similar to Python's convention: https://docs.python.org/3/c-api/apiabiversion.html
+// Additional convention: 0xD = dev
+#define PYBIND11_VERSION_HEX 0x020603D1
+
 #define PYBIND11_NAMESPACE_BEGIN(name) namespace name {
 #define PYBIND11_NAMESPACE_END(name) }
 

noxfile.py

@@ -53,14 +53,18 @@ def docs(session: nox.Session) -> None:
 
     session.install("-r", "docs/requirements.txt")
     session.chdir("docs")
+
+    if "pdf" in session.posargs:
+        session.run("sphinx-build", "-M", "latexpdf", ".", "_build")
+        return
+
     session.run("sphinx-build", "-M", "html", ".", "_build")
 
-    if session.posargs:
-        if "serve" in session.posargs:
-            print("Launching docs at http://localhost:8000/ - use Ctrl-C to quit")
-            session.run("python", "-m", "http.server", "8000", "-d", "_build/html")
-        else:
-            print("Unsupported argument to docs")
+    if "serve" in session.posargs:
+        session.log("Launching docs at http://localhost:8000/ - use Ctrl-C to quit")
+        session.run("python", "-m", "http.server", "8000", "-d", "_build/html")
+    elif session.posargs:
+        session.error("Unsupported argument to docs")
 
 
 @nox.session(reuse_venv=True)

setup.py

@@ -19,6 +19,36 @@ VERSION_REGEX = re.compile(
     r"^\s*#\s*define\s+PYBIND11_VERSION_([A-Z]+)\s+(.*)$", re.MULTILINE
 )
 
+
+def build_expected_version_hex(matches):
+    patch_level_serial = matches["PATCH"]
+    serial = None
+    try:
+        major = int(matches["MAJOR"])
+        minor = int(matches["MINOR"])
+        flds = patch_level_serial.split(".")
+        if flds:
+            patch = int(flds[0])
+            level = None
+            if len(flds) == 1:
+                level = "0"
+                serial = 0
+            elif len(flds) == 2:
+                level_serial = flds[1]
+                for level in ("a", "b", "c", "dev"):
+                    if level_serial.startswith(level):
+                        serial = int(level_serial[len(level) :])
+                        break
+    except ValueError:
+        pass
+    if serial is None:
+        msg = 'Invalid PYBIND11_VERSION_PATCH: "{}"'.format(patch_level_serial)
+        raise RuntimeError(msg)
+    return "0x{:02x}{:02x}{:02x}{}{:x}".format(
+        major, minor, patch, level[:1].upper(), serial
+    )
+
+
 # PYBIND11_GLOBAL_SDIST will build a different sdist, with the python-headers
 # files, and the sys.prefix files (CMake and headers).
 
@@ -49,6 +79,15 @@ if version != cpp_version:
     )
     raise RuntimeError(msg)
 
+version_hex = matches.get("HEX", "MISSING")
+expected_version_hex = build_expected_version_hex(matches)
+if version_hex != expected_version_hex:
+    msg = "PYBIND11_VERSION_HEX {} does not match expected value {}!".format(
+        version_hex,
+        expected_version_hex,
+    )
+    raise RuntimeError(msg)
+
 
 def get_and_replace(filename, binary=False, **opts):
     with open(filename, "rb" if binary else "r") as f:

tools/setup_main.py.in

@@ -32,6 +32,9 @@ setup(
     entry_points={
         "console_scripts": [
              "pybind11-config = pybind11.__main__:main",
+        ],
+        "pipx.run": [
+             "pybind11 = pybind11.__main__:main",
         ]
     },
     cmdclass=cmdclass