Add EMCC_LOGGING=0 to disable all logging

This can be useful when running tests that want to check the stderr
of emscripten.

This was suggested as an aternative to #19085 and should fix #18607 but
maybe isn't quite right to solve #18622.

Fixes: #19085

ChangeLog.md

@@ -20,6 +20,9 @@ See docs/process.md for more on how version tagging works.
 
 3.1.41 (in development)
 -----------------------
+- The log message that emcc will sometime print (for example when auto-building
+  system libraries) can now be completely supressed by running with
+  `EMCC_LOGGING=0`.
 - A new setting (`CHECK_NULL_WRITES`) was added to disabled the checking of
   address zero that is normally done when `STACK_OVERFLOW_CHECK` is enabled.
   (#19487)

test/test_other.py

@@ -7118,6 +7118,7 @@ def test_realpath_2(self):
 Resolved: "/" => "/"
 ''', self.run_js('a.out.js'))
 
+  @with_env_modify({'EMCC_LOGGING': '0'})  # this test assumes no emcc output
   def test_no_warnings(self):
     # build once before to make sure system libs etc. exist
     self.run_process([EMXX, test_file('hello_libcxx.cpp')])
@@ -11281,10 +11282,8 @@ def test_bitcode_input(self):
     self.run_process([EMCC, '-c', '-o', 'main.o', 'main.bc'])
     self.assertTrue(building.is_wasm('main.o'))
 
+  @with_env_modify({'EMCC_LOGGING': '0'})  # this test assumes no emcc output
   def test_nostdlib(self):
-    # First ensure all the system libs are built
-    self.run_process([EMCC, test_file('unistd/close.c')])
-
     err = 'symbol exported via --export not found: __errno_location'
     self.assertContained(err, self.expect_fail([EMCC, test_file('unistd/close.c'), '-nostdlib']))
     self.assertContained(err, self.expect_fail([EMCC, test_file('unistd/close.c'), '-nodefaultlibs']))

tools/shared.py

@@ -29,9 +29,14 @@
 # Configure logging before importing any other local modules so even
 # log message during import are shown as expected.
 DEBUG = int(os.environ.get('EMCC_DEBUG', '0'))
+EMCC_LOGGING = int(os.environ.get('EMCC_LOGGING', '1'))
+log_level = logging.ERROR
+if DEBUG:
+  log_level = logging.DEBUG
+elif EMCC_LOGGING:
+  log_level = logging.INFO
 # can add  %(asctime)s  to see timestamps
-logging.basicConfig(format='%(name)s:%(levelname)s: %(message)s',
-                    level=logging.DEBUG if DEBUG else logging.INFO)
+logging.basicConfig(format='%(name)s:%(levelname)s: %(message)s', level=log_level)
 colored_logger.enable()
 
 from .utils import path_from_root, exit_with_error, safe_ensure_dirs, WINDOWS