Fix gmtime handling and add platform defines

Add platform-specific defines for gmtime variants in BUILD.gn (HAVE_GMTIME_R on Linux/ChromeOS/Android/mac/iOS, HAVE_GMTIME_S on Windows). Update cmsplugin.c::_cmsGetTime to guard against gmtime returning NULL: copy the result into ptr_time only if non-NULL and return a boolean success value, avoiding a NULL dereference inside the critical section.

Author: bobsingor

third_party/BUILD.gn

@@ -306,6 +306,12 @@ source_set("fx_lcms2") {
     "lcms/src/cmswtpnt.c",
     "lcms/src/cmsxform.c",
   ]
+  if (is_linux || is_chromeos || is_android || is_mac || is_ios) {
+    defines = [ "HAVE_GMTIME_R" ]
+  }
+  if (is_win) {
+    defines = [ "HAVE_GMTIME_S" ]
+  }
   deps = [ "../core/fxcrt" ]
 }
 

third_party/lcms/src/cmsplugin.c

@@ -1057,7 +1057,10 @@ cmsBool _cmsGetTime(struct tm* ptr_time)
 
     _cmsEnterCriticalSectionPrimitive(&_cmsContextPoolHeadMutex);
     t = gmtime(&now);
+    if (t != NULL)
+        *ptr_time = *t;
     _cmsLeaveCriticalSectionPrimitive(&_cmsContextPoolHeadMutex);
+    return t != NULL;
 #endif
 
     if (t == NULL)