Avoid malloc dependency in tzset

Author: sbc100

src/generated_struct_info32.json

@@ -401,6 +401,7 @@
         "TIOCGWINSZ": 21523,
         "TIOCSPGRP": 21520,
         "TIOCSWINSZ": 21524,
+        "TZNAME_MAX": 6,
         "UUID_TYPE_DCE_RANDOM": 4,
         "UUID_VARIANT_DCE": 1,
         "W_OK": 2,

src/generated_struct_info64.json

@@ -401,6 +401,7 @@
         "TIOCGWINSZ": 21523,
         "TIOCSPGRP": 21520,
         "TIOCSWINSZ": 21524,
+        "TZNAME_MAX": 6,
         "UUID_TYPE_DCE_RANDOM": 4,
         "UUID_VARIANT_DCE": 1,
         "W_OK": 2,

src/library.js

@@ -604,19 +604,22 @@ addToLibrary({
     return ret;
   },
 
-  _tzset_js__deps: ['$stringToNewUTF8'],
+  _tzset_js__deps: ['$stringToUTF8'],
   _tzset_js__internal: true,
-  _tzset_js: (timezone, daylight, tzname) => {
+  _tzset_js: (timezone, daylight, std_name, dst_name) => {
     // TODO: Use (malleable) environment variables instead of system settings.
     var currentYear = new Date().getFullYear();
     var winter = new Date(currentYear, 0, 1);
     var summer = new Date(currentYear, 6, 1);
     var winterOffset = winter.getTimezoneOffset();
     var summerOffset = summer.getTimezoneOffset();
 
-    // Local standard timezone offset. Local standard time is not adjusted for daylight savings.
-    // This code uses the fact that getTimezoneOffset returns a greater value during Standard Time versus Daylight Saving Time (DST).
-    // Thus it determines the expected output during Standard Time, and it compares whether the output of the given date the same (Standard) or less (DST).
+    // Local standard timezone offset. Local standard time is not adjusted for
+    // daylight savings.  This code uses the fact that getTimezoneOffset returns
+    // a greater value during Standard Time versus Daylight Saving Time (DST).
+    // Thus it determines the expected output during Standard Time, and it
+    // compares whether the output of the given date the same (Standard) or less
+    // (DST).
     var stdTimezoneOffset = Math.max(winterOffset, summerOffset);
 
     // timezone is specified as seconds west of UTC ("The external variable
@@ -634,15 +637,13 @@ addToLibrary({
     };
     var winterName = extractZone(winter);
     var summerName = extractZone(summer);
-    var winterNamePtr = stringToNewUTF8(winterName);
-    var summerNamePtr = stringToNewUTF8(summerName);
     if (summerOffset < winterOffset) {
       // Northern hemisphere
-      {{{ makeSetValue('tzname', '0', 'winterNamePtr', POINTER_TYPE) }}};
-      {{{ makeSetValue('tzname', POINTER_SIZE, 'summerNamePtr', POINTER_TYPE) }}};
+      stringToUTF8(winterName, std_name, {{{ cDefs.TZNAME_MAX + 1 }}});
+      stringToUTF8(summerName, dst_name, {{{ cDefs.TZNAME_MAX + 1 }}});
     } else {
-      {{{ makeSetValue('tzname', '0', 'summerNamePtr', POINTER_TYPE) }}};
-      {{{ makeSetValue('tzname', POINTER_SIZE, 'winterNamePtr', POINTER_TYPE) }}};
+      stringToUTF8(winterName, dst_name, {{{ cDefs.TZNAME_MAX + 1 }}});
+      stringToUTF8(summerName, std_name, {{{ cDefs.TZNAME_MAX + 1 }}});
     }
   },
 

src/struct_info.json

@@ -318,6 +318,12 @@
             "X_OK"
         ]
     },
+    {
+        "file": "limits.h",
+        "defines": [
+            "TZNAME_MAX"
+        ]
+    },
     {
         "file": "bits/errno.h",
         "defines": [

system/lib/libc/emscripten_internal.h

@@ -44,7 +44,7 @@ time_t _mktime_js(struct tm* tm);
 void _localtime_js(time_t t, struct tm* __restrict__ tm);
 void _gmtime_js(time_t t, struct tm* __restrict__ tm);
 
-void _tzset_js(long* timezone, int* daylight, char** tzname);
+void _tzset_js(long* timezone, int* daylight, char* std_name, char* dst_name);
 
 const char* emscripten_pc_get_function(uintptr_t pc);
 const char* emscripten_pc_get_file(uintptr_t pc);

system/lib/libc/tzset.c

@@ -4,19 +4,25 @@
  * University of Illinois/NCSA Open Source License.  Both these licenses can be
  * found in the LICENSE file.
  */
+#include <limits.h>
 #include <time.h>
 #include <stdbool.h>
 #include <pthread.h>
 
 #include "emscripten_internal.h"
 
+static char std_name[TZNAME_MAX+1];
+static char dst_name[TZNAME_MAX+1];
+
 weak void tzset() {
   static pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
   static _Atomic bool done_init = false;
   if (!done_init) {
     pthread_mutex_lock(&lock);
     if (!done_init) {
-      _tzset_js(&timezone, &daylight, tzname);
+      _tzset_js(&timezone, &daylight, std_name, dst_name);
+      tzname[0] = std_name;
+      tzname[1] = dst_name;
       done_init = true;
     }
     pthread_mutex_unlock(&lock);