feat(run): support simulation for free-threaded python

Remove PYTHONMALLOC=malloc which is unsupported for free-threaded builds

Author: adriencaccia

src/run/runner/valgrind/helpers/mod.rs

@@ -1,3 +1,4 @@
 pub mod ignored_objects_path;
 pub mod perf_maps;
+pub mod python;
 pub mod venv_compat;

src/run/runner/valgrind/helpers/python.rs

@@ -0,0 +1,21 @@
+use std::process::Command;
+
+/// Checks if the Python interpreter supports free-threaded mode.
+/// Returns true if Python is free-threaded (GIL disabled), false otherwise.
+pub fn is_free_threaded_python() -> bool {
+    // Use sysconfig.get_config_var("Py_GIL_DISABLED") as recommended by Python docs at https://docs.python.org/3/howto/free-threading-python.html#identifying-free-threaded-python
+    let output = Command::new("python")
+        .args([
+            "-c",
+            "import sysconfig; print(sysconfig.get_config_var('Py_GIL_DISABLED') or 0)",
+        ])
+        .output();
+
+    match output {
+        Ok(output) if output.status.success() => {
+            let stdout = String::from_utf8_lossy(&output.stdout);
+            stdout.trim() == "1"
+        }
+        _ => false, // If Python is not available or command fails, assume not free-threaded
+    }
+}

src/run/runner/valgrind/measure.rs

@@ -6,6 +6,7 @@ use crate::run::runner::helpers::introspected_golang;
 use crate::run::runner::helpers::introspected_nodejs;
 use crate::run::runner::helpers::run_command_with_log_pipe::run_command_with_log_pipe;
 use crate::run::runner::valgrind::helpers::ignored_objects_path::get_objects_path_to_ignore;
+use crate::run::runner::valgrind::helpers::python::is_free_threaded_python;
 use crate::run::{config::Config, instruments::mongo_tracer::MongoTracer};
 use lazy_static::lazy_static;
 use std::env;
@@ -87,9 +88,16 @@ pub async fn measure(
     cmd.envs(get_base_injected_env(
         RunnerMode::Simulation,
         profile_folder,
-    ))
-    .env("PYTHONMALLOC", "malloc")
-    .env(
+    ));
+
+    // Only set PYTHONMALLOC=malloc for non-free-threaded Python builds.
+    // Free-threaded Python (with GIL disabled) manages memory differently and
+    // should not have PYTHONMALLOC overridden.
+    if !is_free_threaded_python() {
+        cmd.env("PYTHONMALLOC", "malloc");
+    }
+
+    cmd.env(
         "PATH",
         format!(
             "{}:{}:{}",