Add more warnings to for the ObjC runtime build

Working on https://github.com/google/protobuf/issues/1599, specifically:
- Turn on more warnings that the Xcode UI calls out with individual controls.
- Manually add:
  -Wundef
  -Wswitch-enum
- Manually add and then diable in the unittests because of XCTest's headers:
  -Wreserved-id-macro
  -Wdocumentation-unknown-command
- Manually add -Wdirect-ivar-access, but disable it for the unittests and in
  the library code (via #pragmas to suppress it). This is done so proto users
  can enable the warning.

1 files changed, 9 insertions, 1 deletions

diff --git a/objectivec/GPBDescriptor.m b/objectivec/GPBDescriptor.m
index 2709737c..898f231d 100644
--- a/objectivec/GPBDescriptor.m
+++ b/objectivec/GPBDescriptor.m
@@ -36,6 +36,12 @@
 #import "GPBWireFormat.h"
 #import "GPBMessage_PackagePrivate.h"
 
+// Direct access is use for speed, to avoid even internally declaring things
+// read/write, etc. The warning is enabled in the project to ensure code calling
+// protos can turn on -Wdirect-ivar-access without issues.
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wdirect-ivar-access"
+
 // The address of this variable is used as a key for obj_getAssociatedObject.
 static const char kTextFormatExtraValueKey = 0;
 
@@ -803,7 +809,7 @@ uint32_t GPBFieldAlternateTag(GPBFieldDescriptor *self) {
   if ((self = [super init])) {
     description_ = description;
 
-#if DEBUG
+#if defined(DEBUG) && DEBUG
     const char *className = description->messageOrGroupClassName;
     if (className) {
       NSAssert(objc_lookUpClass(className) != Nil,
@@ -961,3 +967,5 @@ uint32_t GPBFieldAlternateTag(GPBFieldDescriptor *self) {
 }
 
 @end
+
+#pragma clang diagnostic pop