python_toolchain: set and use preprocessor flags for extensions

Author: zsol

examples/with_prelude/cpp/python_cextension/BUCK

@@ -5,9 +5,16 @@
 # WILL BE DELETED. UNLESS THERE IS AN ONCALL ADDED THIS FILE WILL BE
 
 # DELETED WITHOUT NOTICE - DO NOT DEPEND ON IT.
-# FIXME(marwhal): Get python_cextension example working again
-# python_binary(
-#     name = "cext",
-#     deps = ["//cpp/python_cextension:cpprint"],
-#     main = "cext/cext.py"
-# )
+
+cxx_python_extension(
+    name = "cpprint",
+    srcs = ["print.cpp"],
+    base_module = "",
+    visibility = ["PUBLIC"],
+)
+
+python_binary(
+    name = "cext",
+    deps = [":cpprint"],
+    main = "cext.py"
+)

examples/with_prelude/python/use_cextension/BUCK

@@ -30,26 +30,3 @@ static struct PyModuleDef extension = {
 PyMODINIT_FUNC PyInit_cpprint(void) {
   return PyModule_Create(&extension);
 }
-
-int main(int argc, char* argv[]) {
-  wchar_t* program = Py_DecodeLocale(argv[0], NULL);
-  if (program == NULL) {
-    fprintf(stderr, "Fatal error: cannot decode argv[0]\n");
-    exit(1);
-  }
-
-  /* Add a built-in module, before Py_Initialize */
-  if (PyImport_AppendInittab("cppring", PyInit_cpprint) == -1) {
-    fprintf(stderr, "Error: could not extend in-built modules table\n");
-    exit(1);
-  }
-
-  /* Pass argv[0] to the Python interpreter */
-  Py_SetProgramName(program);
-
-  /* Initialize the Python interpreter.  Required.
-     If this step fails, it will be a fatal error. */
-  Py_Initialize();
-
-  return 0;
-}

examples/with_prelude/python/use_cextension/cext/cext.py renamed to examples/with_prelude/python/use_cextension/cext.py

@@ -130,7 +130,7 @@ def cxx_python_extension_impl(ctx: AnalysisContext) -> list[Provider]:
         platform_compiler_flags = ctx.attrs.platform_compiler_flags,
         extra_link_flags = python_toolchain.extension_linker_flags,
         lang_platform_compiler_flags = ctx.attrs.lang_platform_compiler_flags,
-        preprocessor_flags = ctx.attrs.preprocessor_flags,
+        preprocessor_flags = python_toolchain.extension_preprocessor_flags + ctx.attrs.preprocessor_flags,
         lang_preprocessor_flags = ctx.attrs.lang_preprocessor_flags,
         platform_preprocessor_flags = ctx.attrs.platform_preprocessor_flags,
         lang_platform_preprocessor_flags = ctx.attrs.lang_platform_preprocessor_flags,

examples/with_prelude/cpp/python_cextension/print.cpp renamed to examples/with_prelude/python/use_cextension/print.cpp

@@ -59,6 +59,7 @@ PythonToolchainInfo = provider(
         "binary_linker_flags": provider_field(ArgLike, default = []),
         "extension_linker_flags": provider_field(ArgLike, default = []),
         "wheel_linker_flags": provider_field(ArgLike, default = []),
+        "extension_preprocessor_flags": provider_field(list[ArgLike], default = []),
         # site-packages-relative rpaths to emebed into libs/bins in the wheel
         "wheel_rpaths": provider_field(ArgLike, default = []),
         "gen_lpar_bootstrap": provider_field(Dependency | None, default = None),

prelude/python/cxx_python_extension.bzl

@@ -104,6 +104,7 @@ def python_toolchain_impl(ctx) -> list[Provider]:
             linker_flags = [],
             binary_linker_flags = [],
             extension_linker_flags = ctx.attrs.extension_linker_flags,
+            extension_preprocessor_flags = ctx.attrs.extension_preprocessor_flags,
         ),
         PythonPlatformInfo(name = "x86_64"),
     ]
@@ -113,6 +114,7 @@ python_toolchain = rule(
     attrs = {
         "compile": attrs.default_only(attrs.dep(default = "prelude//python/tools:compile.py")),
         "extension_linker_flags": attrs.list(attrs.arg()),
+        "extension_preprocessor_flags": attrs.list(attrs.arg()),
         "interpreter": attrs.dep(providers = [RunInfo]),
     },
     is_toolchain_rule = True,
@@ -204,5 +206,9 @@ def remote_python_toolchain(
             "DEFAULT": ["-L$(location :cpython_archive[lib])", "@$(location :libpython_symbols)"],
             "prelude//os:windows": ["/LIBPATH:$(location :cpython_archive[lib])"],
         }),
+        extension_preprocessor_flags = select({
+            "DEFAULT": ["-I$(location :cpython_archive[include])"],
+            "prelude//os:windows": ["/I$(location :cpython_archive[include])"],
+        }),
         **kwargs
     )