Create lib64 symlink for 64-bit, non-macOS, POSIX environments (#3584)

## Summary

Closes
https://github.com/astral-sh/uv/issues/3578#issuecomment-2110675382.

## Test Plan

Verified that in the OpenSUSE test, we create both, and they're
symlinks:

```text
INFO: Creating virtual environment with `venv`...
INFO: Installing into `venv` virtual environment...
DEBUG Found a virtualenv named .venv at: /tmp/tmp4nape29h/.venv
DEBUG Cached interpreter info for Python 3.10.14, skipping probing: .venv/bin/python
DEBUG Using Python 3.10.14 environment at .venv/bin/python
DEBUG Trying to lock if free: .venv/.lock
purelib: "/tmp/tmp4nape29h/.venv/lib/python3.10/site-packages"
platlib: "/tmp/tmp4nape29h/.venv/lib64/python3.10/site-packages"
is_same_file(purelib, platlib): Ok(true)
```

crates/uv-interpreter/python/get_interpreter_info.py

@@ -555,9 +555,12 @@ def main() -> None:
         "scheme": get_scheme(),
         "virtualenv": get_virtualenv(),
         "platform": get_operating_system_and_architecture(),
-        # The `t` abiflag for freethreading python
+        # The `t` abiflag for freethreading Python.
         # https://peps.python.org/pep-0703/#build-configuration-changes
         "gil_disabled": bool(sysconfig.get_config_var("Py_GIL_DISABLED")),
+        # Determine if the interpreter is 32-bit or 64-bit.
+        # https://github.com/python/cpython/blob/b228655c227b2ca298a8ffac44d14ce3d22f6faa/Lib/venv/__init__.py#L136
+        "pointer_size": "64" if sys.maxsize > 2**32 else "32",
     }
     print(json.dumps(interpreter_info))
 

crates/uv-interpreter/src/interpreter.rs

@@ -17,6 +17,7 @@ use pypi_types::Scheme;
 use uv_cache::{Cache, CacheBucket, CachedByTimestamp, Freshness, Timestamp};
 use uv_fs::{write_atomic_sync, PythonExt, Simplified};
 
+use crate::pointer_size::PointerSize;
 use crate::{Error, PythonVersion, Target, VirtualEnvironment};
 
 /// A Python executable and its associated platform markers.
@@ -35,6 +36,7 @@ pub struct Interpreter {
     stdlib: PathBuf,
     tags: OnceCell<Tags>,
     target: Option<Target>,
+    pointer_size: PointerSize,
     gil_disabled: bool,
 }
 
@@ -56,6 +58,7 @@ impl Interpreter {
             virtualenv: info.virtualenv,
             prefix: info.prefix,
             base_exec_prefix: info.base_exec_prefix,
+            pointer_size: info.pointer_size,
             gil_disabled: info.gil_disabled,
             base_prefix: info.base_prefix,
             base_executable: info.base_executable,
@@ -95,6 +98,7 @@ impl Interpreter {
             stdlib: PathBuf::from("/dev/null"),
             tags: OnceCell::new(),
             target: None,
+            pointer_size: PointerSize::_64,
             gil_disabled: false,
         }
     }
@@ -326,6 +330,11 @@ impl Interpreter {
         &self.virtualenv
     }
 
+    /// Return the [`PointerSize`] of the Python interpreter (i.e., 32- vs. 64-bit).
+    pub fn pointer_size(&self) -> PointerSize {
+        self.pointer_size
+    }
+
     /// Return whether this is a Python 3.13+ freethreading Python, as specified by the sysconfig var
     /// `Py_GIL_DISABLED`.
     ///
@@ -429,6 +438,7 @@ struct InterpreterInfo {
     sys_executable: PathBuf,
     sys_path: Vec<PathBuf>,
     stdlib: PathBuf,
+    pointer_size: PointerSize,
     gil_disabled: bool,
 }
 
@@ -662,6 +672,7 @@ mod tests {
                     "purelib": "lib/python3.12/site-packages",
                     "scripts": "bin"
                 },
+                "pointer_size": "64",
                 "gil_disabled": true
             }
         "##};

crates/uv-interpreter/src/lib.rs

@@ -20,6 +20,7 @@ pub use crate::environment::PythonEnvironment;
 pub use crate::find_python::{find_best_python, find_default_python, find_requested_python};
 pub use crate::interpreter::Interpreter;
 use crate::interpreter::InterpreterInfoError;
+pub use crate::pointer_size::PointerSize;
 pub use crate::python_version::PythonVersion;
 pub use crate::target::Target;
 pub use crate::virtualenv::{PyVenvConfiguration, VirtualEnvironment};
@@ -30,6 +31,7 @@ mod implementation;
 mod interpreter;
 pub mod managed;
 pub mod platform;
+mod pointer_size;
 mod py_launcher;
 mod python_version;
 mod target;

crates/uv-interpreter/src/pointer_size.rs

@@ -0,0 +1,21 @@
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Copy, Clone, Serialize, Deserialize)]
+pub enum PointerSize {
+    /// 32-bit architecture.
+    #[serde(rename = "32")]
+    _32,
+    /// 64-bit architecture.
+    #[serde(rename = "64")]
+    _64,
+}
+
+impl PointerSize {
+    pub const fn is_32(self) -> bool {
+        matches!(self, Self::_32)
+    }
+
+    pub const fn is_64(self) -> bool {
+        matches!(self, Self::_64)
+    }
+}

crates/uv-virtualenv/src/bare.rs

@@ -265,9 +265,27 @@ pub fn create_bare_venv(
 
     // Construct the path to the `site-packages` directory.
     let site_packages = location.join(&interpreter.virtualenv().purelib);
+    fs::create_dir_all(&site_packages)?;
+
+    // If necessary, create a symlink from `lib64` to `lib`.
+    // See: https://github.com/python/cpython/blob/b228655c227b2ca298a8ffac44d14ce3d22f6faa/Lib/venv/__init__.py#L135C11-L135C16
+    #[cfg(unix)]
+    if interpreter.pointer_size().is_64()
+        && interpreter.markers().os_name() == "posix"
+        && interpreter.markers().sys_platform() != "darwin"
+    {
+        let lib64 = location.join("lib64");
+        let lib = location.join("lib");
+        match std::os::unix::fs::symlink(lib, lib64) {
+            Ok(()) => {}
+            Err(err) if err.kind() == io::ErrorKind::AlreadyExists => {}
+            Err(err) => {
+                return Err(err.into());
+            }
+        }
+    }
 
     // Populate `site-packages` with a `_virtualenv.py` file.
-    fs::create_dir_all(&site_packages)?;
     fs::write(site_packages.join("_virtualenv.py"), VIRTUALENV_PATCH)?;
     fs::write(site_packages.join("_virtualenv.pth"), "import _virtualenv")?;