Simplify --cflags emcc flag (#25534)

See #25524

Author: sbc100

emcc.py

@@ -31,13 +31,12 @@
 import tarfile
 from dataclasses import dataclass
 from enum import Enum, auto, unique
-from subprocess import PIPE
 
 
 from tools import shared, system_libs, utils, cmdline
 from tools import diagnostics, building, compile
 from tools.shared import unsuffixed_basename, get_file_suffix
-from tools.shared import run_process, exit_with_error, DEBUG
+from tools.shared import exit_with_error, DEBUG
 from tools.shared import in_temp
 from tools.shared import DYLIB_EXTENSIONS
 from tools.cmdline import CLANG_FLAGS_WITH_ARGS
@@ -242,27 +241,6 @@ def run(args):
     print(utils.EMSCRIPTEN_VERSION)
     return 0
 
-  if '--cflags' in args:
-    # fake running the command, to see the full args we pass to clang
-    args = [x for x in args if x != '--cflags']
-    with shared.get_temp_files().get_file(suffix='.o') as temp_target:
-      input_file = 'hello_world.c'
-      compiler = shared.EMCC
-      if shared.run_via_emxx:
-        compiler = shared.EMXX
-      cmd = [compiler, utils.path_from_root('test', input_file), '-v', '-c', '-o', temp_target] + args
-      proc = run_process(cmd, stderr=PIPE, check=False)
-      if proc.returncode != 0:
-        print(proc.stderr)
-        exit_with_error('error getting cflags')
-      lines = [x for x in proc.stderr.splitlines() if clang in x and input_file in x]
-      if not lines:
-        exit_with_error(f'unable to parse output of `{cmd}`:\n{proc.stderr}')
-      parts = shlex.split(lines[0].replace('\\', '\\\\'))
-      parts = [x for x in parts if x not in ['-c', '-o', '-v', '-emit-llvm'] and input_file not in x and temp_target not in x]
-      print(shlex.join(parts[1:]))
-    return 0
-
   if '-dumpmachine' in args or '-print-target-triple' in args or '--print-target-triple' in args:
     print(shared.get_llvm_target())
     return 0
@@ -314,6 +292,13 @@ def run(args):
 
   phase_setup(options, state)
 
+  if '--cflags' in args:
+    # Just print the flags we pass to clang and exit.  We need to do this after
+    # phase_setup because the setup sets things like SUPPORT_LONGJMP.
+    cflags = compile.get_cflags(x for x in args if x != '--cflags')
+    print(shlex.join(cflags))
+    return 0
+
   if options.reproduce:
     create_reproduce_file(options.reproduce, args)
 

test/test_other.py

@@ -689,19 +689,20 @@ def test_js_transform(self):
     self.assertIn('transformed!', read_file('a.out.js'))
 
   @crossplatform
+  @also_with_wasm64
   def test_emcc_cflags(self):
-    output = self.run_process([EMCC, '--cflags'], stdout=PIPE)
+    output = self.run_process([EMCC, '--cflags'] + self.get_cflags(), stdout=PIPE)
     flags = output.stdout.strip()
-    self.assertContained('-target wasm32-unknown-emscripten', flags)
+    self.assertContained(r'-target wasm\d\d-unknown-emscripten', flags, regex=True)
     self.assertContained('--sysroot=', flags)
-    output = self.run_process([EMXX, '--cflags'], stdout=PIPE)
+    output = self.run_process([EMXX, '--cflags'] + self.get_cflags(), stdout=PIPE)
     flags = output.stdout.strip()
-    self.assertContained('-target wasm32-unknown-emscripten', flags)
+    self.assertContained(r'-target wasm\d\d-unknown-emscripten', flags, regex=True)
     self.assertContained('--sysroot=', flags)
     # check they work
     cmd = [CLANG_CC, test_file('hello_world.c')] + shlex.split(flags.replace('\\', '\\\\')) + ['-c', '-o', 'out.o']
     self.run_process(cmd)
-    self.run_process([EMCC, 'out.o'])
+    self.run_process([EMCC, 'out.o'] + self.get_cflags())
     self.assertContained('hello, world!', self.run_js('a.out.js'))
 
   @crossplatform