From 4a4d884fdfd55c7bbf76110c8f80e0a655b514aa Mon Sep 17 00:00:00 2001
From: Mircea Trofin <mtrofin@google.com>
Date: Wed, 22 Apr 2026 10:23:09 -0700
Subject: [PATCH] Passthrough for `subprocess.Popen` in
 `start_cancellable_process`

---
 compiler_opt/rl/compilation_runner.py       | 17 +++++++++++------
 compiler_opt/rl/compilation_runner_test.py  | 12 +++++++-----
 compiler_opt/rl/inlining/inlining_runner.py |  8 ++++----
 3 files changed, 22 insertions(+), 15 deletions(-)

diff --git a/compiler_opt/rl/compilation_runner.py b/compiler_opt/rl/compilation_runner.py
index 3d48213c..bdd50e77 100644
--- a/compiler_opt/rl/compilation_runner.py
+++ b/compiler_opt/rl/compilation_runner.py
@@ -208,11 +208,14 @@ def __del__(self):
       raise RuntimeError('Cancellation manager deleted while containing items.')
 
 
-def start_cancellable_process(cmdline: list[str],
-                              timeout: float,
-                              cancellation_manager: WorkerCancellationManager
-                              | None,
-                              want_output: bool = False) -> bytes | None:
+def start_cancellable_process(
+    cmdline: list[str],
+    timeout: float,
+    cancellation_manager: WorkerCancellationManager
+    | None,
+    want_output: bool = False,
+    **kwargs,
+) -> bytes | str | None:
   """Start a cancellable process.
 
   Args:
@@ -237,7 +240,9 @@ def start_cancellable_process(cmdline: list[str],
   with subprocess.Popen(
       cmdline,
       env=command_env,
-      stdout=(subprocess.PIPE if want_output else None)) as p:
+      stdout=(subprocess.PIPE if want_output else None),
+      **kwargs,
+  ) as p:
     if cancellation_manager:
       cancellation_manager.register_process(p)
 
diff --git a/compiler_opt/rl/compilation_runner_test.py b/compiler_opt/rl/compilation_runner_test.py
index 874b9cbc..011c8110 100644
--- a/compiler_opt/rl/compilation_runner_test.py
+++ b/compiler_opt/rl/compilation_runner_test.py
@@ -217,11 +217,13 @@ def test_exception_handling(self, mock_compile_fn):
 
   def test_start_subprocess_output(self):
     cm = compilation_runner.WorkerCancellationManager()
-    output = compilation_runner.start_cancellable_process(
-        ['ls', '-l'], timeout=100, cancellation_manager=cm, want_output=True)
-    if output:
-      output_str = output.decode('utf-8')
-    else:
+    output_str = compilation_runner.start_cancellable_process(
+        ['ls', '-l'],
+        timeout=100,
+        cancellation_manager=cm,
+        want_output=True,
+        text=True)
+    if not output_str:
       self.fail('output should have been non-empty')
     self.assertNotEmpty(output_str)
 
diff --git a/compiler_opt/rl/inlining/inlining_runner.py b/compiler_opt/rl/inlining/inlining_runner.py
index 2fbb41a6..54332ee8 100644
--- a/compiler_opt/rl/inlining/inlining_runner.py
+++ b/compiler_opt/rl/inlining/inlining_runner.py
@@ -97,14 +97,14 @@ def compile_and_get_size(self, command_line: corpus.FullyQualifiedCmdLine,
                                                  self._compilation_timeout,
                                                  self._cancellation_manager)
     cmdline = [self._llvm_size_path, output_native_path]
-    output_bytes = compilation_runner.start_cancellable_process(
+    output = compilation_runner.start_cancellable_process(
         cmdline,
         timeout=self._compilation_timeout,
         cancellation_manager=self._cancellation_manager,
-        want_output=True)
-    if not output_bytes:
+        want_output=True,
+        text=True)
+    if not output:
       raise RuntimeError(f'Empty llvm-size output: {" ".join(cmdline)}')
-    output = output_bytes.decode('utf-8')
     tmp = output.split('\n')
     if len(tmp) != 3:
       raise RuntimeError(f'Wrong llvm-size output {output}')