Bug 1471685 - Work around MSVC linker adding padding during incremental builds. r=froydnj

--HG--
extra : rebase_source : 0e6f711d5f8517ca37d39c6f5a39cd0c0e3ec387

python/mozbuild/mozbuild/action/check_binary.py

@@ -214,8 +214,17 @@ def check_nsmodules(target, binary):
 
     symbols = sorted(symbols)
     next_addr = None
+    # MSVC linker, when doing incremental linking, adds padding when
+    # merging sections. Allow there to be more space between the NSModule
+    # symbols, as long as they are in the right order.
+    if buildconfig.substs.get('_MSC_VER') and \
+            buildconfig.substs.get('DEVELOPER_OPTIONS'):
+        sym_cmp = lambda guessed, actual: guessed <= actual
+    else:
+        sym_cmp = lambda guessed, actual: guessed == actual
+
     for addr, size, sym in symbols:
-        if next_addr is not None and next_addr != addr:
+        if next_addr is not None and not sym_cmp(next_addr, addr):
             print_symbols(symbols)
             raise RuntimeError('NSModules are not adjacent')
         next_addr = addr + size

xpcom/components/nsComponentManager.cpp

@@ -363,7 +363,10 @@ nsComponentManagerImpl::Init()
   RegisterModule(&kXPCOMModule, nullptr);
 
   for (auto module : AllStaticModules()) {
-    RegisterModule(module, nullptr);
+    if (module) { // On local Windows builds, the list may contain null
+                  // pointers from padding.
+      RegisterModule(module, nullptr);
+    }
   }
 
   for (uint32_t i = 0; i < sExtraStaticModules->Length(); ++i) {