From de06fc092339e1d5a159077087da74568bfda778 Mon Sep 17 00:00:00 2001
From: Bas Schoenmaeckers <7943856+bschoenmaeckers@users.noreply.github.com>
Date: Wed, 20 May 2026 15:18:06 +0200
Subject: [PATCH] Add eval function to c-api (#7927)

* Add eval function to c-api

* Extract `Py_CompileString` start values into constants
---
 crates/capi/Cargo.toml   |  2 +-
 crates/capi/src/ceval.rs | 95 ++++++++++++++++++++++++++++++++++++++++
 crates/capi/src/lib.rs   |  1 +
 3 files changed, 97 insertions(+), 1 deletion(-)
 create mode 100644 crates/capi/src/ceval.rs

diff --git a/crates/capi/Cargo.toml b/crates/capi/Cargo.toml
index e9dc8de00..85f42934a 100644
--- a/crates/capi/Cargo.toml
+++ b/crates/capi/Cargo.toml
@@ -12,7 +12,7 @@ license.workspace = true
 crate-type = ["cdylib", "rlib"]
 
 [dependencies]
-rustpython-vm = { workspace = true, features = ["threading"] }
+rustpython-vm = { workspace = true, features = ["threading", "compiler"] }
 rustpython-stdlib = {workspace = true, features = ["threading"] }
 
 [dev-dependencies]
diff --git a/crates/capi/src/ceval.rs b/crates/capi/src/ceval.rs
new file mode 100644
index 000000000..be8d9c48b
--- /dev/null
+++ b/crates/capi/src/ceval.rs
@@ -0,0 +1,95 @@
+use crate::pystate::with_vm;
+use core::ffi::{CStr, c_char, c_int};
+use core::ptr::NonNull;
+use rustpython_vm::builtins::{PyCode, PyDict};
+use rustpython_vm::compiler::Mode;
+use rustpython_vm::function::ArgMapping;
+use rustpython_vm::scope::Scope;
+use rustpython_vm::{AsObject, PyObject, TryFromObject};
+
+const PY_SINGLE_INPUT: c_int = 256;
+const PY_FILE_INPUT: c_int = 257;
+const PY_EVAL_INPUT: c_int = 258;
+const PY_FUNC_TYPE_INPUT: c_int = 345;
+
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn Py_CompileString(
+    code: *const c_char,
+    filename: *const c_char,
+    start: c_int,
+) -> *mut PyObject {
+    with_vm(|vm| {
+        let code = unsafe { CStr::from_ptr(code) }.to_str().map_err(|_| {
+            vm.new_system_error("Py_CompileString called with non UTF-8 code string")
+        })?;
+        let filename = unsafe { CStr::from_ptr(filename) }
+            .to_str()
+            .map_err(|_| vm.new_system_error("Py_CompileString called with non UTF-8 filename"))?;
+
+        let mode = match start {
+            PY_SINGLE_INPUT => Mode::Single,
+            PY_FILE_INPUT => Mode::Exec,
+            PY_EVAL_INPUT => Mode::Eval,
+            PY_FUNC_TYPE_INPUT => Mode::BlockExpr,
+            _ => {
+                return Err(
+                    vm.new_system_error("Invalid start argument passed to Py_CompileString")
+                );
+            }
+        };
+
+        vm.compile(code, mode, filename.to_owned())
+            .map_err(|err| vm.new_syntax_error(&err, Some(code)))
+    })
+}
+
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn PyEval_EvalCode(
+    co: *mut PyObject,
+    globals: *mut PyObject,
+    locals: *mut PyObject,
+) -> *mut PyObject {
+    with_vm(|vm| {
+        let code = unsafe { &*co }.try_downcast_ref::<PyCode>(vm)?;
+        let globals = unsafe { &*globals }.try_downcast_ref::<PyDict>(vm)?;
+        let locals = NonNull::new(locals)
+            .map(|ptr| ArgMapping::try_from_object(vm, unsafe { ptr.as_ref() }.to_owned()))
+            .transpose()?;
+
+        let scope = Scope::with_builtins(locals, globals.to_owned(), vm);
+
+        vm.run_code_obj(code.to_owned(), scope)
+    })
+}
+
+#[unsafe(no_mangle)]
+pub extern "C" fn PyEval_GetBuiltins() -> *mut PyObject {
+    with_vm(|vm| {
+        vm.current_frame().map_or_else(
+            || vm.builtins.as_object().as_raw(),
+            |frame| frame.builtins.as_object().as_raw(),
+        )
+    })
+}
+
+#[cfg(false)]
+mod tests {
+    use pyo3::exceptions::PyException;
+    use pyo3::prelude::*;
+
+    #[test]
+    fn test_code_eval() {
+        Python::attach(|py| {
+            let result = py.eval(c"1 + 1", None, None).unwrap();
+            assert_eq!(result.extract::<u32>().unwrap(), 2);
+        })
+    }
+
+    #[test]
+    fn test_code_run_exception() {
+        Python::attach(|py| {
+            let err = py.run(c"raise Exception()", None, None).unwrap_err();
+            assert!(err.is_instance_of::<PyException>(py));
+        })
+    }
+}
diff --git a/crates/capi/src/lib.rs b/crates/capi/src/lib.rs
index 7196ad233..ac7bdf5ef 100644
--- a/crates/capi/src/lib.rs
+++ b/crates/capi/src/lib.rs
@@ -10,6 +10,7 @@ extern crate alloc;
 
 pub mod abstract_;
 pub mod bytesobject;
+pub mod ceval;
 pub mod import;
 pub mod longobject;
 pub mod object;