Add support for -### compiler flag (#20475)

From the gcc man page:

```
-###
  Like -v except the commands are not executed and arguments are quoted unless they
  contain only alphanumeric characters or "./-_".  This is useful for shell scripts to
  capture the driver-generated command lines.
```

Fixes: #20468

Author: sbc100

embuilder.py

@@ -198,7 +198,7 @@ def main():
     settings.LTO = args.lto
 
   if args.verbose:
-    shared.PRINT_STAGES = True
+    shared.PRINT_SUBPROCS = True
 
   if args.pic:
     settings.RELOCATABLE = 1

emcc.py

@@ -1257,7 +1257,8 @@ def run(args):
   state = EmccState(args)
   options, newargs = phase_parse_arguments(state)
 
-  shared.check_sanity()
+  if not shared.SKIP_SUBPROCS:
+    shared.check_sanity()
 
   if 'EMMAKEN_NO_SDK' in os.environ:
     exit_with_error('EMMAKEN_NO_SDK is no longer supported.  The standard -nostdlib and -nostdinc flags should be used instead')
@@ -1331,7 +1332,7 @@ def run(args):
     return 0
 
   js_syms = {}
-  if not settings.SIDE_MODULE or settings.ASYNCIFY:
+  if (not settings.SIDE_MODULE or settings.ASYNCIFY) and not shared.SKIP_SUBPROCS:
     js_info = get_js_sym_info()
     if not settings.SIDE_MODULE:
       js_syms = js_info['deps']
@@ -3128,7 +3129,7 @@ def compile_source_file(i, input_file):
       cmd += ['-Xclang', '-split-dwarf-file', '-Xclang', unsuffixed_basename(input_file) + '.dwo']
       cmd += ['-Xclang', '-split-dwarf-output', '-Xclang', unsuffixed_basename(input_file) + '.dwo']
     shared.check_call(cmd)
-    if output_file not in ('-', os.devnull):
+    if output_file not in ('-', os.devnull) and not shared.SKIP_SUBPROCS:
       assert os.path.exists(output_file)
 
   # First, generate LLVM bitcode. For each input file, we get base.o with bitcode
@@ -3229,6 +3230,9 @@ def phase_emscript(options, in_wasm, wasm_target, memfile, js_syms):
 
   settings.SUPPORT_BASE64_EMBEDDING = embed_memfile(options)
 
+  if shared.SKIP_SUBPROCS:
+    return
+
   emscripten.run(in_wasm, wasm_target, final_js, memfile, js_syms)
   save_intermediate('original')
 
@@ -3315,6 +3319,9 @@ def create_worker_file(input_file, target_dir, output_file):
 def phase_final_emitting(options, state, target, wasm_target, memfile):
   global final_js
 
+  if shared.SKIP_SUBPROCS:
+    return
+
   target_dir = os.path.dirname(os.path.abspath(target))
   if settings.PTHREADS:
     create_worker_file('src/worker.js', target_dir, settings.PTHREAD_WORKER_FILE)
@@ -3601,7 +3608,9 @@ def consume_arg_file():
     elif check_flag('--ignore-dynamic-linking'):
       options.ignore_dynamic_linking = True
     elif arg == '-v':
-      shared.PRINT_STAGES = True
+      shared.PRINT_SUBPROCS = True
+    elif arg == '-###':
+      shared.SKIP_SUBPROCS = True
     elif check_arg('--shell-file'):
       options.shell_path = consume_arg_file()
     elif check_arg('--source-map-base'):

emsymbolizer.py

@@ -246,7 +246,7 @@ def get_args():
   parser.add_argument('address', help='Address to lookup')
   args = parser.parse_args()
   if args.verbose:
-    shared.PRINT_STAGES = 1
+    shared.PRINT_SUBPROCS = 1
     shared.DEBUG = True
   return args
 

test/test_other.py

@@ -28,7 +28,7 @@
 
 from tools.shared import config
 from tools.shared import EMCC, EMXX, EMAR, EMRANLIB, FILE_PACKAGER, WINDOWS, LLVM_NM
-from tools.shared import CLANG_CC, CLANG_CXX, LLVM_AR, LLVM_DWARFDUMP, LLVM_DWP, EMCMAKE, EMCONFIGURE
+from tools.shared import CLANG_CC, CLANG_CXX, LLVM_AR, LLVM_DWARFDUMP, LLVM_DWP, EMCMAKE, EMCONFIGURE, WASM_LD
 from common import RunnerCore, path_from_root, is_slow_test, ensure_dir, disabled, make_executable
 from common import env_modify, no_mac, no_windows, only_windows, requires_native_clang, with_env_modify
 from common import create_file, parameterized, NON_ZERO, node_pthreads, TEST_ROOT, test_file
@@ -257,6 +257,21 @@ def test_emcc_v(self):
       self.assertContained('Target: wasm32-unknown-emscripten', proc.stderr)
       self.assertNotContained('this is dangerous', proc.stderr)
 
+  def test_log_subcommands(self):
+    # `-v` when combined with other arguments will trace the subcommands
+    # that get run
+    proc = self.run_process([EMCC, '-v', test_file('hello_world.c')], stdout=PIPE, stderr=PIPE)
+    self.assertContained(CLANG_CC, proc.stderr)
+    self.assertContained(WASM_LD, proc.stderr)
+    self.assertExists('a.out.js')
+
+  def test_skip_subcommands(self):
+    # The -### flag is like `-v` but it doesn't actaully execute the sub-commands
+    proc = self.run_process([EMCC, '-###', test_file('hello_world.c')], stdout=PIPE, stderr=PIPE)
+    self.assertContained(CLANG_CC, proc.stderr)
+    self.assertContained(WASM_LD, proc.stderr)
+    self.assertNotExists('a.out.js')
+
   def test_emcc_check(self):
     proc = self.run_process([EMCC, '--check'], stdout=PIPE, stderr=PIPE)
     self.assertEqual(proc.stdout, '')

tools/shared.py

@@ -49,7 +49,9 @@
 
 
 DEBUG_SAVE = DEBUG or int(os.environ.get('EMCC_DEBUG_SAVE', '0'))
-PRINT_STAGES = int(os.getenv('EMCC_VERBOSE', '0'))
+PRINT_SUBPROCS = int(os.getenv('EMCC_VERBOSE', '0'))
+SKIP_SUBPROCS = False
+
 # Minimum node version required to run the emscripten compiler.  This is distinct
 # from the minimum version required to execute the generated code.  This is not an
 # exact requirement, but is the oldest version of node that we do any testing with.
@@ -225,6 +227,8 @@ def get_finished_process():
 def check_call(cmd, *args, **kw):
   """Like `run_process` above but treat failures as fatal and exit_with_error."""
   print_compiler_stage(cmd)
+  if SKIP_SUBPROCS:
+    return 0
   try:
     return run_process(cmd, *args, **kw)
   except subprocess.CalledProcessError as e:
@@ -616,10 +620,20 @@ def target_environment_may_be(environment):
 
 
 def print_compiler_stage(cmd):
-  """Emulate the '-v' of clang/gcc by printing the name of the sub-command
-  before executing it."""
-  if PRINT_STAGES:
-    print(' "%s" %s' % (cmd[0], shlex_join(cmd[1:])), file=sys.stderr)
+  """Emulate the '-v/-###' flags of clang/gcc by printing the sub-commands
+  that we run."""
+
+  def maybe_quote(arg):
+    if all(c.isalnum() or c in './-_' for c in arg):
+      return arg
+    else:
+      return f'"{arg}"'
+
+  if SKIP_SUBPROCS:
+    print(' ' + ' '.join([maybe_quote(a) for a in cmd]), file=sys.stderr)
+    sys.stderr.flush()
+  elif PRINT_SUBPROCS:
+    print(' %s %s' % (maybe_quote(cmd[0]), shlex_join(cmd[1:])), file=sys.stderr)
     sys.stderr.flush()
 
 

tools/system_libs.py

@@ -140,7 +140,7 @@ def get_top_level_ninja_file():
 def run_ninja(build_dir):
   diagnostics.warning('experimental', 'ninja support is experimental')
   cmd = ['ninja', '-C', build_dir, f'-j{shared.get_num_cores()}']
-  if shared.PRINT_STAGES:
+  if shared.PRINT_SUBPROCS:
     cmd.append('-v')
   shared.check_call(cmd, env=clean_env())