Add zeroMemory JS utility function to avoid _memset. NFC (#14441)

This avoids the extra export from wasm and the potential
codesize of including memset.  Its probably faster and
smaller over the wire too.

Using TypedArray:fill looks fine on all the current
min browser versions we support:
https://caniuse.com/mdn-javascript_builtins_typedarray_fill

If we need to support even older browsers we can always
ifdef/polyfill at this single location in the future.

Author: sbc100

src/library.js

@@ -38,6 +38,18 @@ LibraryManager.library = {
     setTempRet0(val);
   },
 
+  $zeroMemory: function(address, size) {
+#if LEGACY_VM_SUPPORT
+    if (!HEAPU8.fill) {
+      for (var i = 0; i < size; i++) {
+        HEAPU8[address + i] = 0;
+      }
+      return;
+    }
+#endif
+    HEAPU8.fill(0, address, address + size);
+  },
+
 #if SAFE_HEAP
   // Trivial wrappers around runtime functions that make these symbols available
   // to native code.
@@ -1490,12 +1502,13 @@ LibraryManager.library = {
   // sys/times.h
   // ==========================================================================
 
+  times__deps: ['$zeroMemory'],
   times: function(buffer) {
     // clock_t times(struct tms *buffer);
     // http://pubs.opengroup.org/onlinepubs/009695399/functions/times.html
     // NOTE: This is fake, since we can't calculate real CPU time usage in JS.
     if (buffer !== 0) {
-      _memset(buffer, 0, {{{ C_STRUCTS.tms.__size__ }}});
+      zeroMemory(buffer, {{{ C_STRUCTS.tms.__size__ }}});
     }
     return 0;
   },
@@ -2040,23 +2053,22 @@ LibraryManager.library = {
 
     return { family: family, addr: addr, port: port };
   },
-  $writeSockaddr__deps: ['$Sockets', '$inetPton4', '$inetPton6'],
+  $writeSockaddr__deps: ['$Sockets', '$inetPton4', '$inetPton6', '$zeroMemory'],
   $writeSockaddr: function (sa, family, addr, port, addrlen) {
     switch (family) {
       case {{{ cDefine('AF_INET') }}}:
         addr = inetPton4(addr);
+        zeroMemory(sa, {{{ C_STRUCTS.sockaddr_in.__size__ }}});
         if (addrlen) {
           {{{ makeSetValue('addrlen', 0, C_STRUCTS.sockaddr_in.__size__, 'i32') }}};
         }
         {{{ makeSetValue('sa', C_STRUCTS.sockaddr_in.sin_family, 'family', 'i16') }}};
         {{{ makeSetValue('sa', C_STRUCTS.sockaddr_in.sin_addr.s_addr, 'addr', 'i32') }}};
         {{{ makeSetValue('sa', C_STRUCTS.sockaddr_in.sin_port, '_htons(port)', 'i16') }}};
-        /* Use makeSetValue instead of memset to avoid adding memset dependency for all users of writeSockaddr. */
-        {{{ assert(C_STRUCTS.sockaddr_in.__size__ - C_STRUCTS.sockaddr_in.sin_zero == 8), '' }}}
-        {{{ makeSetValue('sa', C_STRUCTS.sockaddr_in.sin_zero, '0', 'i64') }}};
         break;
       case {{{ cDefine('AF_INET6') }}}:
         addr = inetPton6(addr);
+        zeroMemory(sa, {{{ C_STRUCTS.sockaddr_in6.__size__ }}});
         if (addrlen) {
           {{{ makeSetValue('addrlen', 0, C_STRUCTS.sockaddr_in6.__size__, 'i32') }}};
         }
@@ -2066,8 +2078,6 @@ LibraryManager.library = {
         {{{ makeSetValue('sa', C_STRUCTS.sockaddr_in6.sin6_addr.__in6_union.__s6_addr+8, 'addr[2]', 'i32') }}};
         {{{ makeSetValue('sa', C_STRUCTS.sockaddr_in6.sin6_addr.__in6_union.__s6_addr+12, 'addr[3]', 'i32') }}};
         {{{ makeSetValue('sa', C_STRUCTS.sockaddr_in6.sin6_port, '_htons(port)', 'i16') }}};
-        {{{ makeSetValue('sa', C_STRUCTS.sockaddr_in6.sin6_flowinfo, '0', 'i32') }}};
-        {{{ makeSetValue('sa', C_STRUCTS.sockaddr_in6.sin6_scope_id, '0', 'i32') }}};
         break;
       default:
         return {{{ cDefine('EAFNOSUPPORT') }}};

src/library_sdl.js

@@ -1348,6 +1348,7 @@ var LibrarySDL = {
     return SDL.version;
   },
 
+  SDL_Init__deps: ['$zeroMemory'],
   SDL_Init__proxy: 'sync',
   SDL_Init__sig: 'ii',
   SDL_Init__docs: '/** @param{number=} initFlags */', 
@@ -1368,7 +1369,7 @@ var LibrarySDL = {
 
     window.addEventListener("unload", SDL.receiveEvent);
     SDL.keyboardState = _malloc(0x10000); // Our SDL needs 512, but 64K is safe for older SDLs
-    _memset(SDL.keyboardState, 0, 0x10000);
+    zeroMemory(SDL.keyboardState, 0x10000);
     // Initialize this structure carefully for closure
     SDL.DOMEventToSDLEvent['keydown']    = 0x300  /* SDL_KEYDOWN */;
     SDL.DOMEventToSDLEvent['keyup']      = 0x301  /* SDL_KEYUP */;

src/library_syscall.js

@@ -226,7 +226,7 @@ var SyscallsLibrary = {
     }
   },
 
-  $syscallMmap2__deps: ['$SYSCALLS',
+  $syscallMmap2__deps: ['$SYSCALLS', '$zeroMemory',
 #if FILESYSTEM && SYSCALLS_REQUIRE_FILESYSTEM
     '$FS',
 #endif
@@ -247,7 +247,7 @@ var SyscallsLibrary = {
     if ((flags & {{{ cDefine('MAP_ANONYMOUS') }}}) !== 0) {
       ptr = _memalign({{{ WASM_PAGE_SIZE }}}, len);
       if (!ptr) return -{{{ cDefine('ENOMEM') }}};
-      _memset(ptr, 0, len);
+      zeroMemory(ptr, len);
       allocated = true;
     } else {
 #if FILESYSTEM && SYSCALLS_REQUIRE_FILESYSTEM
@@ -494,11 +494,12 @@ var SyscallsLibrary = {
   __sys_setrlimit: function(varargs) {
     return 0; // no-op
   },
+  __sys_getrusage__deps: ['$zeroMemory'],
   __sys_getrusage: function(who, usage) {
 #if SYSCALL_DEBUG
     err('warning: untested syscall');
 #endif
-    _memset(usage, 0, {{{ C_STRUCTS.rusage.__size__ }}});
+    zeroMemory(usage, {{{ C_STRUCTS.rusage.__size__ }}});
     {{{ makeSetValue('usage', C_STRUCTS.rusage.ru_utime.tv_sec, '1', 'i32') }}}; // fake some values
     {{{ makeSetValue('usage', C_STRUCTS.rusage.ru_utime.tv_usec, '2', 'i32') }}};
     {{{ makeSetValue('usage', C_STRUCTS.rusage.ru_stime.tv_sec, '3', 'i32') }}};

src/library_uuid.js

@@ -8,9 +8,10 @@
 
 mergeInto(LibraryManager.library, {
   // Clear a 'compact' UUID.
+  uuid_clear__deps: ['$zeroMemory'],
   uuid_clear: function(uu) {
     // void uuid_clear(uuid_t uu);
-    _memset(uu, 0, 16);
+    zeroMemory(uu, 16);
   },
 
   // Compare whether or not two 'compact' UUIDs are the same.

src/settings.js

@@ -598,6 +598,7 @@ var POLYFILL_OLD_MATH_FUNCTIONS = 0;
 //  * Work around old Chromium WebGL 1 bug (-s WORKAROUND_OLD_WEBGL_UNIFORM_UPLOAD_IGNORED_OFFSET_BUG=1)
 //  * Disable WebAssembly. (Must be paired with -s WASM=0)
 //  * Adjusts MIN_X_VERSION settings to 0 to include support for all browser versions.
+//  * Avoid TypedArray.fill, if necessary, in zeroMemory utility function.
 // You can also configure the above options individually.
 // [link]
 var LEGACY_VM_SUPPORT = 0;

tools/deps_info.py

@@ -54,7 +54,7 @@
   'Mix_LoadWAV_RW': ['fileno'],
   'SDL_CreateRGBSurface': ['malloc', 'free'],
   'SDL_GL_GetProcAddress': ['malloc'],
-  'SDL_Init': ['malloc', 'free', 'memset', 'memcpy'],
+  'SDL_Init': ['malloc', 'free', 'memcpy'],
   'SDL_LockSurface': ['malloc', 'free'],
   'SDL_OpenAudio': ['malloc', 'free'],
   'SDL_PushEvent': ['malloc', 'free'],
@@ -160,7 +160,6 @@
   'getnameinfo': ['htons', 'ntohs'],
   'getpeername': ['htons'],
   'getsockname': ['htons'],
-  'getrusage': ['memset'],
   'glGetString': ['malloc'],
   'glGetStringi': ['malloc'],
   'glMapBufferRange': ['malloc'],
@@ -173,7 +172,7 @@
   'localtime': ['_get_tzname', '_get_daylight', '_get_timezone', 'malloc'],
   'localtime_r': ['_get_tzname', '_get_daylight', '_get_timezone', 'malloc'],
   'mktime': ['_get_tzname', '_get_daylight', '_get_timezone', 'malloc'],
-  'mmap': ['memalign', 'memset', 'malloc'],
+  'mmap': ['memalign', 'malloc'],
   'munmap': ['malloc', 'free'],
   'pthread_create': ['malloc', 'free', 'emscripten_main_thread_process_queued_calls'],
   'readdir': ['malloc'],
@@ -193,11 +192,9 @@
   'setgroups': ['sysconf'],
   'syslog': ['malloc', 'ntohs'],
   'timegm': ['_get_tzname', '_get_daylight', '_get_timezone', 'malloc'],
-  'times': ['memset'],
   'tmpnam': ['malloc'],
   'ttyname': ['malloc'],
   'tzset': ['_get_tzname', '_get_daylight', '_get_timezone', 'malloc'],
-  'uuid_clear': ['memset'],
   'uuid_compare': ['memcmp'],
   'uuid_copy': ['memcpy'],
   'wgpuBufferGetMappedRange': ['malloc', 'free'],