Update pybind to 2.6.0 (pytorch#46415)

Summary:
Preserve PYBIND11 (pytorch@63ce3fb) configuration options in `torch._C._PYBIND11 (https://github.com/pytorch/pytorch/commit/63ce3fbde85672e112411ad731839e6db3c15c08)_COMPILER_TYPE` and use them when building extensions

Also, use f-strings in `torch.utils.cpp_extension`

"Fixes" pytorch#46367

Pull Request resolved: pytorch#46415

Reviewed By: VitalyFedyunin

Differential Revision: D24605949

Pulled By: malfet

fbshipit-source-id: 87340f2ed5308266a46ef8f0317316227dab9d4d

Author: malfet

.flake8

@@ -12,5 +12,5 @@ ignore =
     B007,B008,
     # these ignores are from flake8-comprehensions; please fix!
     C400,C401,C402,C403,C404,C405,C407,C411,C413,C414,C415
-per-file-ignores = __init__.py: F401
+per-file-ignores = __init__.py: F401 torch/utils/cpp_extension.py: B950
 exclude = docs/src,venv,third_party,caffe2,scripts,docs/caffe2,torch/lib/include,torch/lib/tmp_install,build,torch/include,*.pyi,.git,build,build_test_custom_build,build_code_analyzer

third_party/pybind11

@@ -864,6 +864,29 @@ Call this whenever a new thread is created in order to propagate values from
   ASSERT_TRUE(set_module_attr("_GLIBCXX_USE_CXX11_ABI", Py_False));
 #endif
 
+// See note [Pybind11 ABI constants]
+#define SET_STR_DEFINE(name) \
+  ASSERT_TRUE(set_module_attr("_" # name, THPUtils_packString(name)))
+
+#ifdef PYBIND11_COMPILER_TYPE
+  SET_STR_DEFINE(PYBIND11_COMPILER_TYPE);
+#else
+  ASSERT_TRUE(set_module_attr("_" C10_STRINGIZE(PYBIND11_COMPILER_TYPE), Py_None));
+#endif
+
+#ifdef PYBIND11_STDLIB
+  SET_STR_DEFINE(PYBIND11_STDLIB);
+#else
+  ASSERT_TRUE(set_module_attr("_" C10_STRINGIZE(PYBIND11_STDLIB), Py_None));
+#endif
+
+#ifdef PYBIND11_BUILD_ABI
+  SET_STR_DEFINE(PYBIND11_BUILD_ABI);
+#else
+  ASSERT_TRUE(set_module_attr("_" C10_STRINGIZE(PYBIND11_BUILD_ABI), Py_None));
+#endif
+#undef SET_STR_DEFINE
+
   const auto& defaultGenerator = at::detail::getDefaultCPUGenerator();
   THPDefaultCPUGenerator = (THPGenerator*)THPGenerator_initDefaultGenerator(defaultGenerator);
   // This reference is meant to be given away, so no need to incref here.

torch/csrc/Module.cpp

@@ -364,6 +364,11 @@ def build_extensions(self) -> None:
                         extension.extra_compile_args[ext] = []
 
             self._add_compile_flag(extension, '-DTORCH_API_INCLUDE_EXTENSION_H')
+            # See note [Pybind11 ABI constants]
+            for name in ["COMPILER_TYPE", "STDLIB", "BUILD_ABI"]:
+                val = getattr(torch._C, f"_PYBIND11_{name}")
+                if val is not None and not IS_WINDOWS:
+                    self._add_compile_flag(extension, f'-DPYBIND11_{name}="{val}"')
             self._define_torch_extension_name(extension)
             self._add_gnu_cpp_abi_flag(extension)
 
@@ -1590,6 +1595,24 @@ def _write_ninja_file_to_build_library(path,
 
     common_cflags = [f'-DTORCH_EXTENSION_NAME={name}']
     common_cflags.append('-DTORCH_API_INCLUDE_EXTENSION_H')
+
+    # Note [Pybind11 ABI constants]
+    #
+    # Pybind11 before 2.4 used to build an ABI strings using the following pattern:
+    # f"__pybind11_internals_v{PYBIND11_INTERNALS_VERSION}{PYBIND11_INTERNALS_KIND}{PYBIND11_BUILD_TYPE}__"
+    # Since 2.4 compier type, stdlib and build abi parameters are also encoded like this:
+    # f"__pybind11_internals_v{PYBIND11_INTERNALS_VERSION}{PYBIND11_INTERNALS_KIND}{PYBIND11_COMPILER_TYPE}{PYBIND11_STDLIB}{PYBIND11_BUILD_ABI}{PYBIND11_BUILD_TYPE}__"
+    #
+    # This was done in order to further narrow down the chances of compiler ABI incompatibility
+    # that can cause a hard to debug segfaults.
+    # For PyTorch extensions we want to relax those restrictions and pass compiler, stdlib and abi properties
+    # captured during PyTorch native library compilation in torch/csrc/Module.cpp
+
+    for pname in ["COMPILER_TYPE", "STDLIB", "BUILD_ABI"]:
+        pval = getattr(torch._C, f"_PYBIND11_{pname}")
+        if pval is not None and not IS_WINDOWS:
+            common_cflags.append(f'-DPYBIND11_{pname}=\\"{pval}\\"')
+
     common_cflags += [f'-I{include}' for include in user_includes]
     common_cflags += [f'-isystem {include}' for include in system_includes]