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Emscripten: No extra rustc-cdylib-link-args on Rust >= 1.95 #5874

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Merged
davidhewitt merged 2 commits into from
Mar 13, 2026
+24 −4
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Emscripten: No extra rustc-cdylib-link-args on Rust >= 1.95 #5874

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2d583f7
Emscripten: No extra rustc-cdylib-link-args on Rust >= 1.95
hoodmane Mar 11, 2026
b2c960a
Update pyo3-build-config/src/lib.rs
davidhewitt Mar 13, 2026
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28 changes: 24 additions & 4 deletions pyo3-build-config/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -56,19 +56,29 @@ pub fn use_pyo3_cfgs() {
///
/// The following link flags are added:
/// - macOS: `-undefined dynamic_lookup`
/// - wasm32-unknown-emscripten: `-sSIDE_MODULE=2 -sWASM_BIGINT`
/// - wasm32-unknown-emscripten: for Rust <= 1.95, `-sSIDE_MODULE=2 -sWASM_BIGINT`
///
/// All other platforms currently are no-ops, however this may change as necessary
/// in future.
pub fn add_extension_module_link_args() {
_add_extension_module_link_args(&impl_::target_triple_from_env(), std::io::stdout())
_add_extension_module_link_args(
&impl_::target_triple_from_env(),
std::io::stdout(),
rustc_minor_version(),
)
}

fn _add_extension_module_link_args(triple: &Triple, mut writer: impl std::io::Write) {
fn _add_extension_module_link_args(
triple: &Triple,
mut writer: impl std::io::Write,
rustc_minor_version: Option<u32>,
) {
if matches!(triple.operating_system, OperatingSystem::Darwin(_)) {
writeln!(writer, "cargo:rustc-cdylib-link-arg=-undefined").unwrap();
writeln!(writer, "cargo:rustc-cdylib-link-arg=dynamic_lookup").unwrap();
} else if triple == &Triple::from_str("wasm32-unknown-emscripten").unwrap() {
} else if triple == &Triple::from_str("wasm32-unknown-emscripten").unwrap()
&& rustc_minor_version.is_some_and(|version| version < 95)
{
writeln!(writer, "cargo:rustc-cdylib-link-arg=-sSIDE_MODULE=2").unwrap();
writeln!(writer, "cargo:rustc-cdylib-link-arg=-sWASM_BIGINT").unwrap();
}
Expand Down Expand Up @@ -415,12 +425,14 @@ mod tests {
_add_extension_module_link_args(
&Triple::from_str("x86_64-pc-windows-msvc").unwrap(),
&mut buf,
None,
);
assert_eq!(buf, Vec::new());

_add_extension_module_link_args(
&Triple::from_str("x86_64-apple-darwin").unwrap(),
&mut buf,
None,
);
assert_eq!(
std::str::from_utf8(&buf).unwrap(),
Expand All @@ -432,12 +444,20 @@ mod tests {
_add_extension_module_link_args(
&Triple::from_str("wasm32-unknown-emscripten").unwrap(),
&mut buf,
Some(94),
);
assert_eq!(
std::str::from_utf8(&buf).unwrap(),
"cargo:rustc-cdylib-link-arg=-sSIDE_MODULE=2\n\
cargo:rustc-cdylib-link-arg=-sWASM_BIGINT\n"
);
buf.clear();
_add_extension_module_link_args(
&Triple::from_str("wasm32-unknown-emscripten").unwrap(),
&mut buf,
Some(95),
);
assert_eq!(std::str::from_utf8(&buf).unwrap(), "");
}

#[cfg(feature = "resolve-config")]
Expand Down
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