From 2c0116280bf741c3cbe89bfcda39bde10dc99d39 Mon Sep 17 00:00:00 2001
From: Sam Clegg <sbc@chromium.org>
Date: Wed, 10 Jun 2026 12:16:05 -0700
Subject: [PATCH] Honor clang resource dir in `-print-file-name` +
 `-print-search-dirs`. NFC

---
 emcc.py            | 29 ++++++++++++++++++++---------
 test/test_other.py | 22 ++++++++++++++--------
 2 files changed, 34 insertions(+), 17 deletions(-)

diff --git a/emcc.py b/emcc.py
index db64d9b046fd7..b3fcb00321127 100644
--- a/emcc.py
+++ b/emcc.py
@@ -29,6 +29,7 @@
 import tarfile
 from dataclasses import dataclass
 from enum import Enum, auto, unique
+from subprocess import PIPE
 
 # This assert needs to happen early, before any too-recent python syntax is used.
 # In particular it needs to happen before we import any python file that uses the
@@ -172,6 +173,15 @@ def make_relative(filename):
       reproduce_file.add(rsp_name, os.path.join(root, 'response.txt'))
 
 
+def get_clang_resource_dir(args):
+  resource_dir = [a for a in args if a.startswith(('-resource-dir=', '--resource-dir='))]
+  if resource_dir:
+    return resource_dir[-1].split('=')[1]
+  else:
+    output = utils.run_process([shared.CLANG_CC, '-print-resource-dir'], stdout=PIPE).stdout
+    return output.strip()
+
+
 @ToolchainProfiler.profile()
 def main(args):
   if shared.run_via_emxx:
@@ -253,7 +263,9 @@ def main(args):
 
   if '-print-search-dirs' in args or '--print-search-dirs' in args:
     print(f'programs: ={config.LLVM_ROOT}')
-    print(f'libraries: ={cache.get_lib_dir(absolute=True)}')
+    resource_dir = get_clang_resource_dir(args)
+    libdir = cache.get_lib_dir(absolute=True)
+    print(f'libraries: ={resource_dir}{os.pathsep}{libdir}')
     return 0
 
   if '-print-libgcc-file-name' in args or '--print-libgcc-file-name' in args:
@@ -265,14 +277,13 @@ def main(args):
   print_file_name = [a for a in args if a.startswith(('-print-file-name=', '--print-file-name='))]
   if print_file_name:
     libname = print_file_name[-1].split('=')[1]
-    resource_dir = [a for a in args if a.startswith(('-resource-dir=', '--resource-dir='))]
-    if resource_dir:
-      system_libpath = resource_dir[-1].split('=')[1]
-    else:
-      system_libpath = cache.get_lib_dir(absolute=True)
-    fullpath = os.path.join(system_libpath, libname)
-    if os.path.isfile(fullpath):
-      print(fullpath)
+    resource_dir = get_clang_resource_dir(args)
+    system_libpath = cache.get_lib_dir(absolute=True)
+    for dirname in (resource_dir, system_libpath):
+      fullpath = os.path.join(dirname, libname)
+      if os.path.isfile(fullpath):
+        print(fullpath)
+        break
     else:
       print(libname)
     return 0
diff --git a/test/test_other.py b/test/test_other.py
index 725c3b3fb5e0e..9718f62e9a30b 100644
--- a/test/test_other.py
+++ b/test/test_other.py
@@ -768,8 +768,8 @@ def test_print_prog_name(self):
   def test_print_file_name(self, args):
     # make sure the corresponding version of libc exists in the cache
     self.run_process([EMCC, test_file('hello_world.c'), '-O2'] + args)
-    output = self.run_process([EMCC, '-print-file-name=libc.a'] + args, stdout=PIPE).stdout
-    output2 = self.run_process([EMCC, '--print-file-name=libc.a'] + args, stdout=PIPE).stdout
+    output = self.run_process([EMCC, '-print-file-name=libc.a'] + args, stdout=PIPE).stdout.rstrip()
+    output2 = self.run_process([EMCC, '--print-file-name=libc.a'] + args, stdout=PIPE).stdout.rstrip()
     self.assertEqual(output, output2)
     filename = Path(output)
     settings.LTO = '-flto' in args
@@ -777,12 +777,18 @@ def test_print_file_name(self, args):
     self.assertContained(cache.get_lib_name('libc.a'), str(filename))
 
   @crossplatform
-  def test_print_file_name_with_resource_dir(self):
-    file = Path(EMCC).name
-    output = self.run_process([EMCC, f'-print-file-name={file}'], stdout=PIPE).stdout
-    output_relative = self.run_process([EMCC, '-resource-dir=' + path_from_root(), f'-print-file-name={file}'], stdout=PIPE).stdout
-    self.assertNotExists(output.rstrip())
-    self.assertExists(output_relative.rstrip())
+  def test_print_file_name_resdir(self):
+    output = self.run_process([EMCC, '-print-file-name=include/wmmintrin.h'], stdout=PIPE).stdout.rstrip()
+    print('print-file-name: ' + output)
+    self.assertExists(output)
+
+  @crossplatform
+  def test_print_file_name_custom_resdir(self):
+    output = self.run_process([EMCC, '-print-file-name=emcc.py'], stdout=PIPE).stdout.rstrip()
+    self.assertNotExists(output)
+
+    output_relative = self.run_process([EMCC, '-resource-dir=' + path_from_root(), '-print-file-name=emcc.py'], stdout=PIPE).stdout.rstrip()
+    self.assertExists(output_relative)
 
   def test_emar_em_config_flag(self):
     # Test that the --em-config flag is accepted but not passed down do llvm-ar.