Fix Windows build by linking _PyDict_NewPresized via raw-dylib after PyO3 0.29

build.rs

@@ -1,10 +1,26 @@
+use std::{env, fs, path::Path};
+
 fn main() {
     pyo3_build_config::use_pyo3_cfgs();
+    let config = pyo3_build_config::get();
     if matches!(
-        pyo3_build_config::get().implementation(),
+        config.implementation(),
         pyo3_build_config::PythonImplementation::CPython
     ) {
         println!("cargo:rustc-cfg=CPython");
     }
     println!("cargo:rustc-check-cfg=cfg(CPython)");
+
+    let link = match env::var("CARGO_CFG_TARGET_OS").as_deref() {
+        Ok("windows") => format!(
+            r#"#[link(name = "{}", kind = "raw-dylib")]"#,
+            config.lib_name().unwrap()
+        ),
+        _ => String::new(),
+    };
+    let out = Path::new(&env::var("OUT_DIR").unwrap()).join("extern_libpython.rs");
+    let src = format!(
+        "macro_rules! extern_libpython {{ ($($t:tt)*) => {{ {link} extern \"C\" {{ $($t)* }} }} }}"
+    );
+    fs::write(out, src).unwrap();
 }

src/ffi/sys.rs

@@ -2,6 +2,10 @@
 
 use pyo3::ffi;
 
-extern "C" {
+include!(concat!(env!("OUT_DIR"), "/extern_libpython.rs"));
+
+extern_libpython! {
+    // x86 Windows import names drop one leading `_`.
+    #[cfg_attr(all(windows, target_arch = "x86"), link_name = "__PyDict_NewPresized")]
     pub(crate) fn _PyDict_NewPresized(minused: ffi::Py_ssize_t) -> *mut ffi::PyObject;
 }