bazel: stub InitRunFiles, fix RUNFILES_* env leak in tcl_library_init

bazel/BUILD

@@ -124,18 +124,12 @@ cc_library(
     }),
 )
 
-# shim old library as it is still referenced in src/sta, implementing the
-# old behavior.
+# Stub library kept for src/sta:opensta compatibility.
+# Tcl setup is now handled by //bazel:tcl_library_init.
 cc_library(
     name = "runfiles",
     srcs = ["InitRunFiles.cpp"],
-    data = [":tcl_resources_dir"],
     visibility = ["//visibility:public"],
-    deps = [
-        "@rules_cc//cc/runfiles",
-        "@tcl_lang//:tcl",
-    ],
-    alwayslink = True,
 )
 
 # small build test to check if "bazel build //src/sta:StaTclInitVar" works

bazel/InitRunFiles.cpp

@@ -1,86 +1,3 @@
-// SPDX-License-Identifier: BSD-3-Clause
-// Copyright (c) 2026, The OpenROAD Authors
-
-// This file to go away as soon as we use the tcl_library_init initialization
-// in OpenSTA.
-
-#include <unistd.h>  // readlink()
-
-#include <climits>
-#include <cstdlib>
-#include <filesystem>
-#include <iostream>
-#include <memory>
-#include <optional>
-#include <string>
-#include <system_error>
-
-#if defined(__APPLE__)
-#include <mach-o/dyld.h>
-#include <sys/param.h>
-#endif
-
-#include "rules_cc/cc/runfiles/runfiles.h"
-
-namespace {
-// Avoid adding any dependencies like boost.filesystem
-// Returns path to running binary if possible, otherwise nullopt.
-static std::optional<std::string> GetProgramLocation()
-{
-#if defined(_WIN32)
-  char result[MAX_PATH + 1] = {'\0'};
-  auto path_len = GetModuleFileNameA(NULL, result, MAX_PATH);
-#elif defined(__APPLE__)
-  char result[MAXPATHLEN + 1] = {'\0'};
-  uint32_t path_len = MAXPATHLEN;
-  if (_NSGetExecutablePath(result, &path_len) != 0) {
-    path_len = readlink(result, result, MAXPATHLEN);
-  }
-#else
-  char result[PATH_MAX + 1] = {'\0'};
-  ssize_t path_len = readlink("/proc/self/exe", result, PATH_MAX);
-#endif
-  if (path_len > 0) {
-    return result;
-  }
-  return std::nullopt;
-}
-
-std::string GetTclLibraryBaseLocation()
-{
-  using rules_cc::cc::runfiles::Runfiles;
-  std::string error;
-  std::unique_ptr<Runfiles> runfiles(Runfiles::Create(
-      *GetProgramLocation(), BAZEL_CURRENT_REPOSITORY, &error));
-  if (!runfiles) {
-    std::cerr << "[Warning] Failed to create bazel runfiles: " << error << "\n";
-    return "";
-  }
-
-  std::error_code ec;
-  for (const std::string loc : {"openroad", "opensta", "_main"}) {
-    const std::string check_loc = loc + "/bazel/tcl_resources_dir";
-    const std::string path = runfiles->Rlocation(check_loc);
-    if (!path.empty() && std::filesystem::exists(path, ec)) {
-      return path;
-    }
-  }
-  return "";
-}
-
-class BazelInitializer
-{
- public:
-  BazelInitializer()
-  {
-    const std::string lib_mount_point = GetTclLibraryBaseLocation();
-    if (!lib_mount_point.empty()) {
-      const std::string tcl_path = lib_mount_point + "/library";
-      setenv("TCL_LIBRARY", tcl_path.c_str(), true);
-    }
-  }
-};
-
-// Provide via global constructor.
-static BazelInitializer bazel_initializer;
-}  // namespace
+// Intentionally empty: tcl_library_init now handles Tcl setup.
+// This file is kept because src/sta:opensta still references
+// //bazel:runfiles in its srcs.

bazel/tcl_library_init.cc

@@ -40,6 +40,21 @@ static std::optional<std::string> TclLibraryMountPoint(Tcl_Interp* interp)
   return Tcl_GetStringResult(interp);
 #else
   using rules_cc::cc::runfiles::Runfiles;
+
+  // Clear inherited RUNFILES_* env vars: when OpenROAD is invoked by
+  // a build system that previously ran another Bazel binary (e.g. a
+  // Python wrapper), those variables point to the *other* binary's
+  // runfiles tree.  Runfiles::Create() checks env vars first, so it
+  // would resolve paths in the wrong tree.  Unsetting forces it to
+  // fall back to the exe path, which is always correct.
+#ifdef _WIN32
+  _putenv_s("RUNFILES_DIR", "");
+  _putenv_s("RUNFILES_MANIFEST_FILE", "");
+#else
+  unsetenv("RUNFILES_DIR");
+  unsetenv("RUNFILES_MANIFEST_FILE");
+#endif
+
   std::string error;
   // Use /proc/self/exe to resolve the real binary path, as argv[0] may
   // point into a sandbox where the .runfiles tree does not exist.

test/runfiles/BUILD

@@ -0,0 +1,14 @@
+# SPDX-License-Identifier: BSD-3-Clause
+# Copyright (c) 2026, The OpenROAD Authors
+
+load("@rules_shell//shell:sh_test.bzl", "sh_test")
+
+# Prove that the unsetenv(RUNFILES_DIR) fix in //bazel:tcl_library_init
+# is necessary: this Bazel test has RUNFILES_DIR pointing to its own
+# runfiles tree, yet OpenROAD must still find *its* TCL library.
+sh_test(
+    name = "runfiles_env_test",
+    srcs = ["runfiles_env_test.sh"],
+    args = ["$(rootpath //:openroad)"],
+    data = ["//:openroad"],
+)

test/runfiles/runfiles_env_test.sh

@@ -0,0 +1,43 @@
+#!/usr/bin/env bash
+# Test that OpenROAD works when invoked from a Bazel-built process
+# that has RUNFILES_DIR / RUNFILES_MANIFEST_FILE set in the environment.
+#
+# This is the scenario that happens when a Bazel py_binary (e.g. a
+# Python wrapper) runs OpenROAD as a subprocess.  The inherited
+# RUNFILES_* variables point to the wrapper's runfiles tree, not
+# OpenROAD's.  Without the unsetenv() fix in tcl_library_init.cc,
+# Runfiles::Create() resolves paths in the wrong tree and OpenROAD
+# fails to find its TCL library.
+#
+# We simulate this by pointing RUNFILES_DIR at an empty directory
+# before invoking OpenROAD.
+
+set -euo pipefail
+
+OPENROAD="$1"
+
+# Simulate cross-binary env leak: point RUNFILES_DIR at an empty
+# directory that does NOT contain OpenROAD's tcl resources.
+FAKE_RUNFILES=$(mktemp -d)
+trap 'rm -rf "$FAKE_RUNFILES"' EXIT
+export RUNFILES_DIR="$FAKE_RUNFILES"
+export RUNFILES_MANIFEST_FILE=""
+echo "Fake RUNFILES_DIR=$RUNFILES_DIR"
+
+# Run OpenROAD with a real Tcl command (not -version, which exits
+# before Tcl init).  Capture both stdout and stderr.
+output=$("$OPENROAD" -no_splash -exit <<< 'puts "TCL_OK"' 2>&1) || {
+    echo "FAIL: openroad exited with $?"
+    echo "$output"
+    exit 1
+}
+
+# Check for Tcl initialization failure
+if echo "$output" | grep -q "application-specific initialization failed"; then
+    echo "FAIL: Tcl library initialization failed despite exe-path fallback"
+    echo "$output"
+    exit 1
+fi
+
+echo "$output"
+echo "PASS: OpenROAD initialized Tcl correctly despite misleading RUNFILES_DIR"