Remove remaining uses of setErrNo and deprecate SUPPORT_ERRNO setting

ChangeLog.md

@@ -57,6 +57,9 @@ See docs/process.md for more on how version tagging works.
 - C++ objects passed into embind's val via constructors, methods, and call
   function will not be automatically destroyed after the function call. This
   makes the behavior consistent for invocations. 
+- The `SUPPORT_ERRNO` setting is now deprecated as it only controlled setting
+  errno from JS library functions and emscripten no longer requires this.
+  (#21074)
 
 3.1.51 - 12/13/23
 -----------------

embuilder.py

@@ -46,7 +46,6 @@
     'libc++-noexcept',
     'libal',
     'libdlmalloc',
-    'libdlmalloc-noerrno',
     'libdlmalloc-tracing',
     'libdlmalloc-debug',
     'libembind',

site/source/docs/tools_reference/settings_reference.rst

@@ -315,6 +315,8 @@ options: 'quiet', 'warn', 'error'. If set to 'warn', Closure warnings are
 printed out to console. If set to 'error', Closure warnings are treated like
 errors, similar to -Werror compiler flag.
 
+.. note:: This setting is deprecated
+
 .. _ignore_closure_compiler_errors:
 
 IGNORE_CLOSURE_COMPILER_ERRORS
@@ -1177,6 +1179,8 @@ EXTRA_EXPORTED_RUNTIME_METHODS
 
 Deprecated, use EXPORTED_RUNTIME_METHODS instead.
 
+.. note:: This setting is deprecated
+
 .. _incoming_module_js_api:
 
 INCOMING_MODULE_JS_API
@@ -2447,13 +2451,11 @@ Minimum supported value is 101900, which was released 2020-02-05.
 SUPPORT_ERRNO
 =============
 
-Tracks whether we are building with errno support enabled. Set to 0
-to disable compiling errno support in altogether. This saves a little
-bit of generated code size in applications that do not care about
-POSIX errno variable. Setting this to 0 also requires using --closure
-for effective code size optimizations to take place.
+Whether we support setting errno from JS library code.
 In MINIMAL_RUNTIME builds, this option defaults to 0.
 
+.. note:: This setting is deprecated
+
 .. _minimal_runtime:
 
 MINIMAL_RUNTIME

src/library.js

@@ -328,8 +328,7 @@ addToLibrary({
     updateMemoryViews();
   },
 
-  system__deps: ['$setErrNo'],
-  system: (command) => {
+  _emscripten_system: (command) => {
 #if ENVIRONMENT_MAY_BE_NODE
     if (ENVIRONMENT_IS_NODE) {
       if (!command) return 1; // shell is available
@@ -368,8 +367,7 @@ addToLibrary({
     // http://pubs.opengroup.org/onlinepubs/000095399/functions/system.html
     // Can't call external programs.
     if (!command) return 0; // no shell available
-    setErrNo({{{ cDefs.ENOSYS }}});
-    return -1;
+    return -{{{ cDefs.ENOSYS }}};
   },
 
   // ==========================================================================
@@ -1522,20 +1520,6 @@ addToLibrary({
     {{{ cDefs.EOWNERDEAD }}}: 'Previous owner died',
     {{{ cDefs.ESTRPIPE }}}: 'Streams pipe error',
   },
-#if SUPPORT_ERRNO
-  $setErrNo__deps: ['__errno_location'],
-  $setErrNo: (value) => {
-    {{{makeSetValue("___errno_location()", 0, 'value', 'i32') }}};
-    return value;
-  },
-#else
-  $setErrNo: (value) => {
-#if ASSERTIONS
-    err('failed to set errno from JS');
-#endif
-    return 0;
-  },
-#endif
 
 #if PROXY_POSIX_SOCKETS == 0
   // ==========================================================================
@@ -2138,11 +2122,10 @@ addToLibrary({
   // nonblocking
   // ==========================================================================
 #if SOCKET_WEBRTC
-  $Sockets__deps: ['$setErrNo',
+  $Sockets__deps: [
     () => 'var SocketIO = ' + read('../third_party/socket.io.js') + ';\n',
-    () => 'var Peer = ' + read('../third_party/wrtcp.js') + ';\n'],
-#else
-  $Sockets__deps: ['$setErrNo'],
+    () => 'var Peer = ' + read('../third_party/wrtcp.js') + ';\n'
+  ],
 #endif
   $Sockets: {
     BUFFER_SIZE: 10*1024, // initial size

src/library_legacy.js

@@ -75,4 +75,19 @@ addToLibrary({
 
   $allocateUTF8: '$stringToNewUTF8',
   $allocateUTF8OnStack: '$stringToUTF8OnStack',
+
+#if SUPPORT_ERRNO
+  $setErrNo__deps: ['__errno_location'],
+  $setErrNo: (value) => {
+    {{{makeSetValue("___errno_location()", 0, 'value', 'i32') }}};
+    return value;
+  },
+#else
+  $setErrNo: (value) => {
+#if ASSERTIONS
+    err('failed to set errno from JS');
+#endif
+    return 0;
+  },
+#endif
 });

src/library_sigs.js

@@ -330,6 +330,7 @@ sigs = {
   _emscripten_receive_on_main_thread_js__sig: 'dipip',
   _emscripten_runtime_keepalive_clear__sig: 'v',
   _emscripten_set_offscreencanvas_size__sig: 'ipii',
+  _emscripten_system__sig: 'ip',
   _emscripten_thread_exit_joinable__sig: 'vp',
   _emscripten_thread_mailbox_await__sig: 'vp',
   _emscripten_thread_set_strongref__sig: 'vp',
@@ -1540,7 +1541,6 @@ sigs = {
   strftime_l__sig: 'pppppp',
   strptime__sig: 'pppp',
   strptime_l__sig: 'ppppp',
-  system__sig: 'ip',
   uuid_clear__sig: 'vp',
   uuid_compare__sig: 'ipp',
   uuid_copy__sig: 'vpp',

src/settings.js

@@ -274,6 +274,7 @@ var USE_CLOSURE_COMPILER = false;
 // printed out to console. If set to 'error', Closure warnings are treated like
 // errors, similar to -Werror compiler flag.
 // [link]
+// [deprecated]
 var CLOSURE_WARNINGS = 'quiet';
 
 // Ignore closure warnings and errors (like on duplicate definitions)
@@ -922,6 +923,7 @@ var ASYNCIFY_EXPORTS = [];
 var EXPORTED_RUNTIME_METHODS = [];
 
 // Deprecated, use EXPORTED_RUNTIME_METHODS instead.
+// [deprecated]
 var EXTRA_EXPORTED_RUNTIME_METHODS = [];
 
 // A list of incoming values on the Module object in JS that we care about. If
@@ -1839,13 +1841,10 @@ var MIN_CHROME_VERSION = 85;
 // Minimum supported value is 101900, which was released 2020-02-05.
 var MIN_NODE_VERSION = 160000;
 
-// Tracks whether we are building with errno support enabled. Set to 0
-// to disable compiling errno support in altogether. This saves a little
-// bit of generated code size in applications that do not care about
-// POSIX errno variable. Setting this to 0 also requires using --closure
-// for effective code size optimizations to take place.
+// Whether we support setting errno from JS library code.
 // In MINIMAL_RUNTIME builds, this option defaults to 0.
 // [link]
+// [deprecated]
 var SUPPORT_ERRNO = true;
 
 // If true, uses minimal sized runtime without POSIX features, Module,

system/lib/libc/emscripten_internal.h

@@ -148,6 +148,8 @@ void llvm_eh_typeid_for(void* exn);
 
 uint32_t _emscripten_lookup_name(const char *name);
 
+int _emscripten_system(const char *command);
+
 #ifdef __cplusplus
 }
 #endif

system/lib/libc/sbrk.c

@@ -12,9 +12,7 @@
 #define __NEED_max_align_t
 #endif
 
-#ifndef EMSCRIPTEN_NO_ERRNO
 #include <errno.h>
-#endif
 #include <limits.h>
 #include <stddef.h>
 #include <stdint.h>
@@ -31,12 +29,6 @@ void emscripten_memprof_sbrk_grow(intptr_t old, intptr_t new);
 
 #include <emscripten/heap.h>
 
-#ifndef EMSCRIPTEN_NO_ERRNO
-#define SET_ERRNO() { errno = ENOMEM; }
-#else
-#define SET_ERRNO()
-#endif
-
 extern size_t __heap_base;
 
 static uintptr_t sbrk_val = (uintptr_t)&__heap_base;
@@ -79,7 +71,7 @@ void *sbrk(intptr_t increment_) {
     // increase the WebAssembly Memory size, and abort if that fails.
     if ((increment > 0 && new_brk <= old_brk)
      || (new_brk > emscripten_get_heap_size() && !emscripten_resize_heap(new_brk))) {
-      SET_ERRNO();
+      errno = ENOMEM;
       return (void*)-1;
     }
 #ifdef __EMSCRIPTEN_SHARED_MEMORY__

system/lib/libc/system.c

@@ -0,0 +1,10 @@
+#include <unistd.h>
+#include <stdlib.h>
+#include <errno.h>
+#include "pthread_impl.h"
+#include "emscripten_internal.h"
+
+int system(const char *cmd)
+{
+	return __syscall_ret(_emscripten_system(cmd));
+}

test/minimal_webgl/CMakeLists.txt

@@ -71,9 +71,6 @@ if (EMSCRIPTEN)
 	# Optimization flag to optimize aggressively for size. (other options -Os, -O3, -O2, -O1, -O0)
 	append_linker_flags("-Oz")
 
-	# Reduce code size: We do not need libc errno field support in our build output.
-	append_linker_flags("-sSUPPORT_ERRNO=0")
-
 	# Reduce code size: We do not need native POSIX filesystem emulation support (Emscripten FS/MEMFS)
 	append_linker_flags("-sFILESYSTEM=0")
 endif()

test/other/metadce/test_metadce_hello_O0.gzsize

@@ -1 +1 @@
-8422
+8420

test/other/metadce/test_metadce_minimal_O0.gzsize

@@ -1 +1 @@
-7251
+7250

test/other/test_unoptimized_code_size_strict.js.size

@@ -1 +1 @@
-57121
+57107

test/test_other.py

@@ -10596,7 +10596,6 @@ def test_minimal_runtime_code_size(self, test_name, js, compare_js_output=False)
                                '-sTEXTDECODER=2',
                                '-sABORTING_MALLOC=0',
                                '-sALLOW_MEMORY_GROWTH=0',
-                               '-sSUPPORT_ERRNO=0',
                                '-sDECLARE_ASM_MODULE_EXPORTS',
                                '-sMALLOC=emmalloc',
                                '-sGL_EMULATE_GLES_VERSION_STRING_FORMAT=0',
@@ -11921,7 +11920,7 @@ def test_default_to_cxx(self):
     'minimal': (['-sMINIMAL_RUNTIME', '-sSUPPORT_ERRNO'],),
   })
   def test_support_errno(self, args):
-    self.emcc_args += args + ['-sEXPORTED_FUNCTIONS=_main,___errno_location']
+    self.emcc_args += args + ['-sEXPORTED_FUNCTIONS=_main,___errno_location', '-Wno-deprecated']
 
     self.do_other_test('test_support_errno.c')
     size_default = os.path.getsize('test_support_errno.js')

tools/link.py

@@ -729,6 +729,9 @@ def phase_linker_setup(options, state, newargs):
 
   final_suffix = get_file_suffix(target)
 
+  if 'SUPPORT_ERRNO' in user_settings:
+    diagnostics.warning('deprecated', 'SUPPORT_ERRNO is deprecated since emscripten no longer uses the setErrNo library function')
+
   if settings.EXTRA_EXPORTED_RUNTIME_METHODS:
     diagnostics.warning('deprecated', 'EXTRA_EXPORTED_RUNTIME_METHODS is deprecated, please use EXPORTED_RUNTIME_METHODS instead')
     settings.EXPORTED_RUNTIME_METHODS += settings.EXTRA_EXPORTED_RUNTIME_METHODS
@@ -879,7 +882,6 @@ def phase_linker_setup(options, state, newargs):
   # It is unlikely that developers targeting "native web" APIs with MINIMAL_RUNTIME need
   # errno support by default.
   if settings.MINIMAL_RUNTIME:
-    default_setting('SUPPORT_ERRNO', 0)
     # Require explicit -lfoo.js flags to link with JS libraries.
     default_setting('AUTO_JS_LIBRARIES', 0)
     # When using MINIMAL_RUNTIME, symbols should only be exported if requested.

tools/maint/update_settings_docs.py

@@ -50,6 +50,7 @@
   'compile+link': 'Applicable during both linking and compilation',
   'compile': 'Only applicable during compilation',
   'experimental': 'This is an experimental setting',
+  'deprecated': 'This setting is deprecated',
 }
 
 output_file = path_from_root('site/source/docs/tools_reference/settings_reference.rst')

tools/system_libs.py

@@ -1267,6 +1267,7 @@ def get_files(self):
           'sigtimedwait.c',
           'wasi-helpers.c',
           'sbrk.c',
+          'system.c',
         ])
 
     if settings.RELOCATABLE:
@@ -1666,7 +1667,6 @@ def __init__(self, **kwargs):
     if self.malloc not in ('dlmalloc', 'emmalloc', 'emmalloc-debug', 'emmalloc-memvalidate', 'emmalloc-verbose', 'emmalloc-memvalidate-verbose', 'mimalloc', 'none'):
       raise Exception('malloc must be one of "emmalloc[-debug|-memvalidate][-verbose]", "dlmalloc" or "none", see settings.js')
 
-    self.use_errno = kwargs.pop('use_errno')
     self.is_tracing = kwargs.pop('is_tracing')
     self.memvalidate = kwargs.pop('memvalidate')
     self.verbose = kwargs.pop('verbose')
@@ -1691,8 +1691,6 @@ def get_cflags(self):
       cflags += ['-UNDEBUG', '-DDLMALLOC_DEBUG']
     else:
       cflags += ['-DNDEBUG']
-    if not self.use_errno:
-      cflags += ['-DMALLOC_FAILURE_ACTION=', '-DEMSCRIPTEN_NO_ERRNO']
     if self.is_tracing:
       cflags += ['--tracing']
     return cflags
@@ -1704,9 +1702,6 @@ def get_base_name(self):
     name = super().get_base_name()
     if self.is_debug and not self.memvalidate and not self.verbose:
       name += '-debug'
-    if not self.use_errno:
-      # emmalloc doesn't actually use errno, but it's easier to build it again
-      name += '-noerrno'
     if self.is_tracing:
       name += '-tracing'
     return name
@@ -1716,14 +1711,13 @@ def can_use(self):
 
   @classmethod
   def vary_on(cls):
-    return super().vary_on() + ['is_debug', 'use_errno', 'is_tracing', 'memvalidate', 'verbose']
+    return super().vary_on() + ['is_debug', 'is_tracing', 'memvalidate', 'verbose']
 
   @classmethod
   def get_default_variation(cls, **kwargs):
     return super().get_default_variation(
       malloc=settings.MALLOC,
       is_debug=settings.ASSERTIONS >= 2,
-      use_errno=settings.SUPPORT_ERRNO,
       is_tracing=settings.EMSCRIPTEN_TRACING,
       memvalidate='memvalidate' in settings.MALLOC,
       verbose='verbose' in settings.MALLOC,