[llvm] [lit] Ensure ulimit does not persist across tests (PR #164485)

[Aiden Grossman via llvm-commits]

https://github.com/boomanaiden154 created https://github.com/llvm/llvm-project/pull/164485

When constructing a container in a default argument in Python, we actually end up with a reference to the same default container for every invocation of the function. Given this happened with the ulimit variable in ShellEnvironment, we ended up persisting limits across tests. This would cause some LLVM tests to fail, particularly jitlink and dsymutil tests, if they ended up running after the one clang test that uses ulimit -v to set a maximum amount of memory that can be allocated. This patch fixes that behavior by constructing the dict inside the function to ensure we get a new instance and adds test coverage.

>From b35a757b8c756984a2deb180e2ee091240b6971e Mon Sep 17 00:00:00 2001
From: Aiden Grossman <aidengrossman at google.com>
Date: Tue, 21 Oct 2025 19:59:33 +0000
Subject: [PATCH] [lit] Ensure ulimit does not persist across tests

When constructing a container in a default argument in Python, we
actually end up with a reference to the same default container for every
invocation of the function. Given this happened with the ulimit variable
in ShellEnvironment, we ended up persisting limits across tests. This
would cause some LLVM tests to fail, particularly jitlink and dsymutil
tests, if they ended up running after the one clang test that uses
ulimit -v to set a maximum amount of memory that can be allocated. This
patch fixes that behavior by constructing the dict inside the function
to ensure we get a new instance and adds test coverage.
---
 llvm/utils/lit/lit/TestRunner.py                           | 4 ++--
 llvm/utils/lit/tests/Inputs/shtest-ulimit/ulimit_reset.txt | 3 +++
 llvm/utils/lit/tests/shtest-ulimit.py                      | 7 +++++--
 3 files changed, 10 insertions(+), 4 deletions(-)
 create mode 100644 llvm/utils/lit/tests/Inputs/shtest-ulimit/ulimit_reset.txt

diff --git a/llvm/utils/lit/lit/TestRunner.py b/llvm/utils/lit/lit/TestRunner.py
index a7e2705f609af..f88314547bb3f 100644
--- a/llvm/utils/lit/lit/TestRunner.py
+++ b/llvm/utils/lit/lit/TestRunner.py
@@ -92,12 +92,12 @@ class ShellEnvironment(object):
     we maintain a dir stack for pushd/popd.
     """
 
-    def __init__(self, cwd, env, umask=-1, ulimit={}):
+    def __init__(self, cwd, env, umask=-1, ulimit=None):
         self.cwd = cwd
         self.env = dict(env)
         self.umask = umask
         self.dirStack = []
-        self.ulimit = ulimit
+        self.ulimit = ulimit if ulimit else {}
 
     def change_dir(self, newdir):
         if os.path.isabs(newdir):
diff --git a/llvm/utils/lit/tests/Inputs/shtest-ulimit/ulimit_reset.txt b/llvm/utils/lit/tests/Inputs/shtest-ulimit/ulimit_reset.txt
new file mode 100644
index 0000000000000..011d6db6c127f
--- /dev/null
+++ b/llvm/utils/lit/tests/Inputs/shtest-ulimit/ulimit_reset.txt
@@ -0,0 +1,3 @@
+# RUN: %{python} %S/print_limits.py
+# Fail the test so that we can assert on the output.
+# RUN: not echo return
diff --git a/llvm/utils/lit/tests/shtest-ulimit.py b/llvm/utils/lit/tests/shtest-ulimit.py
index e84327772d3a1..9a8febd3333c4 100644
--- a/llvm/utils/lit/tests/shtest-ulimit.py
+++ b/llvm/utils/lit/tests/shtest-ulimit.py
@@ -5,9 +5,9 @@
 # as well.
 # UNSUPPORTED: system-windows, system-solaris
 
-# RUN: not %{lit} -a -v %{inputs}/shtest-ulimit | FileCheck %s
+# RUN: not %{lit} -a -v %{inputs}/shtest-ulimit --order=lexical | FileCheck %s
 
-# CHECK: -- Testing: 2 tests{{.*}}
+# CHECK: -- Testing: 3 tests{{.*}}
 
 # CHECK-LABEL: FAIL: shtest-ulimit :: ulimit-bad-arg.txt ({{[^)]*}})
 # CHECK: ulimit -n
@@ -16,3 +16,6 @@
 # CHECK-LABEL: FAIL: shtest-ulimit :: ulimit_okay.txt ({{[^)]*}})
 # CHECK: ulimit -n 50
 # CHECK: RLIMIT_NOFILE=50
+
+# CHECK-LABEL: FAIL: shtest-ulimit :: ulimit_reset.txt ({{[^)]*}})
+# CHECK-NOT: RLIMIT_NOFILE=50