From eaaf382a8c12bc840b253d9ffbc46f378bfaaf54 Mon Sep 17 00:00:00 2001
From: Bas Schoenmaeckers <b.schoenmaeckers@zandersgroup.com>
Date: Thu, 16 Apr 2026 17:44:55 +0200
Subject: [PATCH] Add `RustPython` cfg

---
 pyo3-build-config/src/impl_.rs | 5 +++++
 pyo3-build-config/src/lib.rs   | 2 ++
 pyo3-ffi/build.rs              | 2 ++
 3 files changed, 9 insertions(+)

diff --git a/pyo3-build-config/src/impl_.rs b/pyo3-build-config/src/impl_.rs
index 6a090d93b75..3d64cb34e4c 100644
--- a/pyo3-build-config/src/impl_.rs
+++ b/pyo3-build-config/src/impl_.rs
@@ -191,6 +191,7 @@ impl InterpreterConfig {
             PythonImplementation::CPython => {}
             PythonImplementation::PyPy => out.push("cargo:rustc-cfg=PyPy".to_owned()),
             PythonImplementation::GraalPy => out.push("cargo:rustc-cfg=GraalPy".to_owned()),
+            PythonImplementation::RustPython => out.push("cargo:rustc-cfg=RustPython".to_owned()),
         }
 
         // If Py_GIL_DISABLED is set, do not build with limited API support
@@ -780,6 +781,7 @@ pub enum PythonImplementation {
     CPython,
     PyPy,
     GraalPy,
+    RustPython,
 }
 
 impl PythonImplementation {
@@ -813,6 +815,7 @@ impl Display for PythonImplementation {
             PythonImplementation::CPython => write!(f, "CPython"),
             PythonImplementation::PyPy => write!(f, "PyPy"),
             PythonImplementation::GraalPy => write!(f, "GraalVM"),
+            PythonImplementation::RustPython => write!(f, "RustPython"),
         }
     }
 }
@@ -824,6 +827,7 @@ impl FromStr for PythonImplementation {
             "CPython" => Ok(PythonImplementation::CPython),
             "PyPy" => Ok(PythonImplementation::PyPy),
             "GraalVM" => Ok(PythonImplementation::GraalPy),
+            "RustPython" => Ok(PythonImplementation::RustPython),
             _ => bail!("unknown interpreter: {}", s),
         }
     }
@@ -1768,6 +1772,7 @@ fn default_lib_name_unix(
         },
 
         PythonImplementation::GraalPy => Ok("python-native".to_string()),
+        PythonImplementation::RustPython => Ok("rustpython-capi".to_string()),
     }
 }
 
diff --git a/pyo3-build-config/src/lib.rs b/pyo3-build-config/src/lib.rs
index 65d7f1bade4..9bc9a9c8cc9 100644
--- a/pyo3-build-config/src/lib.rs
+++ b/pyo3-build-config/src/lib.rs
@@ -261,6 +261,7 @@ pub fn print_expected_cfgs() {
     println!("cargo:rustc-check-cfg=cfg(Py_GIL_DISABLED)");
     println!("cargo:rustc-check-cfg=cfg(PyPy)");
     println!("cargo:rustc-check-cfg=cfg(GraalPy)");
+    println!("cargo:rustc-check-cfg=cfg(RustPython)");
     println!("cargo:rustc-check-cfg=cfg(py_sys_config, values(\"Py_DEBUG\", \"Py_REF_DEBUG\", \"Py_TRACE_REFS\", \"COUNT_ALLOCS\"))");
     println!("cargo:rustc-check-cfg=cfg(pyo3_disable_reference_pool)");
     println!("cargo:rustc-check-cfg=cfg(pyo3_leak_on_drop_without_reference_pool)");
@@ -393,6 +394,7 @@ pub mod pyo3_build_script_impl {
                 PythonImplementation::CPython => "Python",
                 PythonImplementation::PyPy => "PyPy",
                 PythonImplementation::GraalPy => "GraalPy",
+                PythonImplementation::RustPython => "RustPython",
             };
             let version = &interpreter_config.version;
             let message = format!(
diff --git a/pyo3-ffi/build.rs b/pyo3-ffi/build.rs
index 127874ffa84..7c9be0e4cb0 100644
--- a/pyo3-ffi/build.rs
+++ b/pyo3-ffi/build.rs
@@ -122,6 +122,7 @@ fn ensure_python_version(interpreter_config: &InterpreterConfig) -> Result<()> {
                 return Err(error.finish().into());
             }
         }
+        PythonImplementation::RustPython => {}
     }
 
     if interpreter_config.abi3 {
@@ -140,6 +141,7 @@ fn ensure_python_version(interpreter_config: &InterpreterConfig) -> Result<()> {
             PythonImplementation::GraalPy => warn!(
                 "GraalPy does not support abi3 so the build artifacts will be version-specific."
             ),
+            PythonImplementation::RustPython => {}
         }
     }