Add native wrapper for dbg() JS function (#18619)

This means we can remove some complexity from the debug system in
`dynlink.c` and other native callers of this function get, for example,
the current thread into prepended to the debug message.

Author: sbc100

src/library.js

@@ -3411,20 +3411,21 @@ mergeInto(LibraryManager.library, {
 
   _emscripten_out__sig: 'vp',
   _emscripten_out: function(str) {
-#if ASSERTIONS
-    assert(typeof str == 'number');
-#endif
     out(UTF8ToString(str));
   },
 
   _emscripten_err__sig: 'vp',
   _emscripten_err: function(str) {
-#if ASSERTIONS
-    assert(typeof str == 'number');
-#endif
     err(UTF8ToString(str));
   },
 
+#if ASSERTIONS || RUNTIME_DEBUG
+  _emscripten_dbg__sig: 'vp',
+  _emscripten_dbg: function(str) {
+    dbg(UTF8ToString(str));
+  },
+#endif
+
   // Use program_invocation_short_name and program_invocation_name in compiled
   // programs. This function is for implementing them.
   _emscripten_get_progname__sig: 'vpp',

src/runtime_debug.js

@@ -129,7 +129,14 @@ function prettyPrint(arg) {
 #if ASSERTIONS || RUNTIME_DEBUG
 // Used by XXXXX_DEBUG settings to output debug messages.
 function dbg(text) {
-  // TODO(sbc): Make this configurable somehow.  Its not always convient for
+#if ENVIRONMENT_MAY_BE_NODE && USE_PTHREADS
+  // Avoid using the console for debugging in multi-threaded node applications
+  // See https://github.com/emscripten-core/emscripten/issues/14804
+  if (ENVIRONMENT_IS_NODE) {
+    fs.writeSync(2, text + '\n');
+  } else
+#endif
+  // TODO(sbc): Make this configurable somehow.  Its not always convenient for
   // logging to show up as errors.
   console.error(text);
 }

src/runtime_strings.js

@@ -105,6 +105,9 @@ function UTF8ArrayToString(heapOrArray, idx, maxBytesToRead) {
  * @return {string}
  */
 function UTF8ToString(ptr, maxBytesToRead) {
+#if ASSERTIONS
+  assert(typeof ptr == 'number');
+#endif
 #if CAN_ADDRESS_2GB
   ptr >>>= 0;
 #endif

src/worker.js

@@ -177,7 +177,7 @@ function handleMessage(e) {
 
       {{{ makeAsmImportsAccessInPthread('buffer') }}} = {{{ makeAsmImportsAccessInPthread('wasmMemory') }}}.buffer;
 
-#if PTHREADS_DEBUG
+#if ASSERTIONS
       Module['workerID'] = e.data.workerID;
 #endif
 

system/include/emscripten/console.h

@@ -25,13 +25,15 @@ void emscripten_console_error(const char *utf8String);
 // See https://github.com/emscripten-core/emscripten/issues/14804
 void _emscripten_out(const char *utf8String);
 void _emscripten_err(const char *utf8String);
+void _emscripten_dbg(const char *utf8String);
 
 // Similar to the above functions but operate with printf-like semantics.
 void emscripten_console_logf(const char *utf8String, ...) __attribute__((__format__(printf, 1, 2)));
 void emscripten_console_warnf(const char *utf8String, ...) __attribute__((__format__(printf, 1, 2)));
 void emscripten_console_errorf(const char *utf8String, ...)__attribute__((__format__(printf, 1, 2)));
 void _emscripten_outf(const char *utf8String, ...) __attribute__((__format__(printf, 1, 2)));
 void _emscripten_errf(const char *utf8String, ...) __attribute__((__format__(printf, 1, 2)));
+void _emscripten_dbgf(const char *utf8String, ...) __attribute__((__format__(printf, 1, 2)));
 
 #ifdef __cplusplus
 }

system/lib/libc/dynlink.c

@@ -25,7 +25,7 @@
 //#define DYLINK_DEBUG
 
 #ifdef DYLINK_DEBUG
-#define dbg(fmt, ...) _emscripten_errf("%p: " fmt, pthread_self(), ##__VA_ARGS__)
+#define dbg(fmt, ...) _emscripten_dbgf(fmt, ##__VA_ARGS__)
 #else
 #define dbg(fmt, ...)
 #endif

system/lib/libc/emscripten_console.c

@@ -54,3 +54,12 @@ void _emscripten_errf(const char* fmt, ...) {
   vlogf(fmt, ap, &_emscripten_err);
   va_end(ap);
 }
+
+#ifndef NDEBUG
+void _emscripten_dbgf(const char* fmt, ...) {
+  va_list ap;
+  va_start(ap, fmt);
+  vlogf(fmt, ap, &_emscripten_dbg);
+  va_end(ap);
+}
+#endif

test/other/test_dbg.c

@@ -0,0 +1,19 @@
+/*
+ * Copyright 2023 The Emscripten Authors.  All rights reserved.
+ * Emscripten is available under two separate licenses, the MIT license and the
+ * University of Illinois/NCSA Open Source License.  Both these licenses can be
+ * found in the LICENSE file.
+ */
+
+#include <stdio.h>
+#include <emscripten/console.h>
+
+int main() {
+  printf("hello, world!\n");
+#ifndef NDEBUG
+  // This symbol is only available in debug builds (i.e. -sASSERTIONS)
+  _emscripten_dbg("native dbg message");
+  _emscripten_dbgf("formatted: %d", 42);
+#endif
+  return 0;
+}

test/test_other.py

@@ -12864,15 +12864,20 @@ def test_dbg(self):
     dbg('start');
     Module.onRuntimeInitialized = () => dbg('done init');
     ''')
+    expected = '''\
+start
+w:0,t:0x[0-9a-fA-F]+: done init
+hello, world!
+w:0,t:0x[0-9a-fA-F]+: native dbg message
+w:0,t:0x[0-9a-fA-F]+: formatted: 42
+'''
     self.emcc_args.append('--pre-js=pre.js')
     # Verify that, after initialization, dbg() messages are prefixed with
     # worker and thread ID.
-    self.do_runf(test_file('hello_world.c'),
-                 'start\nw:0,t:0x[0-9a-fA-F]+: done init\nhello, world!\n',
-                 regex=True)
+    self.do_runf(test_file('other/test_dbg.c'), expected, regex=True)
 
     # When assertions are disabled `dbg` function is not defined
-    self.do_runf(test_file('hello_world.c'),
+    self.do_runf(test_file('other/test_dbg.c'),
                  'ReferenceError: dbg is not defined',
-                 emcc_args=['-sASSERTIONS=0'],
+                 emcc_args=['-DNDEBUG', '-sASSERTIONS=0'],
                  assert_returncode=NON_ZERO)