From 6956a0c3c817c9647d285324ddb46d0d1186a721 Mon Sep 17 00:00:00 2001
From: Sam Clegg <sbc@chromium.org>
Date: Thu, 10 Oct 2024 22:10:20 -0700
Subject: [PATCH] Don't pass `-Xlinker` flags to clang when compiling (#22716)

This avoids a warning about unused linker flags.
---
 emcc.py            | 30 +++++++++++++++++++++++-------
 test/test_other.py |  6 ++++++
 2 files changed, 29 insertions(+), 7 deletions(-)

diff --git a/emcc.py b/emcc.py
index 8ac79fd5efba..617be15c106d 100644
--- a/emcc.py
+++ b/emcc.py
@@ -937,6 +937,28 @@ def get_clang_output_extension(state):
     return '.o'
 
 
+def filter_out_link_flags(args):
+  rtn = []
+
+  def is_link_flag(flag):
+    if flag in ('-nostdlib', '-nostartfiles', '-nolibc', '-nodefaultlibs', '-s'):
+      return True
+    return flag.startswith(('-l', '-L', '-Wl,', '-z'))
+
+  skip = False
+  for arg in args:
+    if skip:
+      skip = False
+      continue
+    if is_link_flag(arg):
+      continue
+    if arg == '-Xlinker':
+      skip = True
+      continue
+    rtn.append(arg)
+  return rtn
+
+
 @ToolchainProfiler.profile_block('compile inputs')
 def phase_compile_inputs(options, state, newargs, input_files):
   if shared.run_via_emxx:
@@ -1016,13 +1038,7 @@ def get_clang_command_asm():
 
   # In COMPILE_AND_LINK we need to compile source files too, but we also need to
   # filter out the link flags
-
-  def is_link_flag(flag):
-    if flag in ('-nostdlib', '-nostartfiles', '-nolibc', '-nodefaultlibs', '-s'):
-      return True
-    return flag.startswith(('-l', '-L', '-Wl,', '-z'))
-
-  compile_args = [a for a in compile_args if a and not is_link_flag(a)]
+  compile_args = filter_out_link_flags(compile_args)
   linker_inputs = []
   seen_names = {}
 
diff --git a/test/test_other.py b/test/test_other.py
index 4b4b17a5a4d1..923a49d1a98e 100644
--- a/test/test_other.py
+++ b/test/test_other.py
@@ -11946,6 +11946,12 @@ def test_linker_flags_unused(self):
     err = self.run_process([EMCC, test_file('hello_world.c'), '-c', '-lbar'], stderr=PIPE).stderr
     self.assertContained("warning: -lbar: 'linker' input unused [-Wunused-command-line-argument]", err)
 
+    # Check that we don't see these "input unused" errors for linker flags when
+    # compiling and linking in single step (i.e. ensure that we don't pass them to clang when
+    # compiling internally).
+    err = self.run_process([EMCC, test_file('hello_world.c'), '-Wl,-static', '-Xlinker', '-static'], stderr=PIPE).stderr
+    self.assertNotContained("input unused", err)
+
   def test_linker_input_unused(self):
     self.run_process([EMCC, '-c', test_file('hello_world.c')])
     err = self.run_process([EMCC, 'hello_world.o', '-c', '-o', 'out.o'], stderr=PIPE).stderr