Reimplement C++ logging (#1313)

* Add direct support for formatting Objective-C objects
* Rewrite log.h
* Convert FSTWarn to LOG_WARN
* Convert FSTLog to LOG_DEBUG
* Remove FSTLogger

22 files changed, 179 insertions, 314 deletions

diff --git a/Firestore/Example/Tests/SpecTests/FSTMockDatastore.mm b/Firestore/Example/Tests/SpecTests/FSTMockDatastore.mm
index dd34556..c846ec5 100644
--- a/Firestore/Example/Tests/SpecTests/FSTMockDatastore.mm
+++ b/Firestore/Example/Tests/SpecTests/FSTMockDatastore.mm
@@ -21,7 +21,6 @@
 #import "Firestore/Source/Remote/FSTSerializerBeta.h"
 #import "Firestore/Source/Remote/FSTStream.h"
 #import "Firestore/Source/Util/FSTAssert.h"
-#import "Firestore/Source/Util/FSTLogger.h"
 
 #import "Firestore/Example/Tests/Remote/FSTWatchChange+Testing.h"
 
@@ -29,6 +28,7 @@
 #include "Firestore/core/src/firebase/firestore/auth/empty_credentials_provider.h"
 #include "Firestore/core/src/firebase/firestore/core/database_info.h"
 #include "Firestore/core/src/firebase/firestore/model/database_id.h"
+#include "Firestore/core/src/firebase/firestore/util/log.h"
 #include "Firestore/core/src/firebase/firestore/util/string_apple.h"
 
 using firebase::firestore::auth::CredentialsProvider;
@@ -117,7 +117,7 @@ NS_ASSUME_NONNULL_BEGIN
 }
 
 - (void)watchQuery:(FSTQueryData *)query {
-  FSTLog(@"watchQuery: %d: %@", query.targetID, query.query);
+  LOG_DEBUG("watchQuery: %s: %s", query.targetID, query.query);
   self.datastore.watchStreamRequestCount += 1;
   // Snapshot version is ignored on the wire
   FSTQueryData *sentQueryData = [query queryDataByReplacingSnapshotVersion:SnapshotVersion::None()
@@ -127,7 +127,7 @@ NS_ASSUME_NONNULL_BEGIN
 }
 
 - (void)unwatchTargetID:(FSTTargetID)targetID {
-  FSTLog(@"unwatchTargetID: %d", targetID);
+  LOG_DEBUG("unwatchTargetID: %s", targetID);
   [self.activeTargets removeObjectForKey:@(targetID)];
 }
 
diff --git a/Firestore/Example/Tests/SpecTests/FSTSpecTests.mm b/Firestore/Example/Tests/SpecTests/FSTSpecTests.mm
index 5a7cb72..7b10bd4 100644
--- a/Firestore/Example/Tests/SpecTests/FSTSpecTests.mm
+++ b/Firestore/Example/Tests/SpecTests/FSTSpecTests.mm
@@ -37,7 +37,6 @@
 #import "Firestore/Source/Util/FSTAssert.h"
 #import "Firestore/Source/Util/FSTClasses.h"
 #import "Firestore/Source/Util/FSTDispatchQueue.h"
-#import "Firestore/Source/Util/FSTLogger.h"
 
 #import "Firestore/Example/Tests/Remote/FSTWatchChange+Testing.h"
 #import "Firestore/Example/Tests/SpecTests/FSTSyncEngineTestDriver.h"
@@ -46,6 +45,7 @@
 #include "Firestore/core/src/firebase/firestore/auth/user.h"
 #include "Firestore/core/src/firebase/firestore/model/document_key.h"
 #include "Firestore/core/src/firebase/firestore/model/snapshot_version.h"
+#include "Firestore/core/src/firebase/firestore/util/log.h"
 #include "Firestore/core/src/firebase/firestore/util/string_apple.h"
 #include "Firestore/core/test/firebase/firestore/testutil/testutil.h"
 
@@ -620,7 +620,7 @@ static NSString *const kNoIOSTag = @"no-ios";
   @try {
     [self setUpForSpecWithConfig:config];
     for (NSDictionary *step in steps) {
-      FSTLog(@"Doing step %@", step);
+      LOG_DEBUG("Doing step %s", step);
       [self doStep:step];
       [self validateStepExpectations:step[@"expect"]];
       [self validateStateExpectations:step[@"stateExpect"]];
diff --git a/Firestore/Example/Tests/SpecTests/FSTSyncEngineTestDriver.mm b/Firestore/Example/Tests/SpecTests/FSTSyncEngineTestDriver.mm
index 2aa0e30..40ebfb9 100644
--- a/Firestore/Example/Tests/SpecTests/FSTSyncEngineTestDriver.mm
+++ b/Firestore/Example/Tests/SpecTests/FSTSyncEngineTestDriver.mm
@@ -31,7 +31,6 @@
 #import "Firestore/Source/Remote/FSTDatastore.h"
 #import "Firestore/Source/Remote/FSTWatchChange.h"
 #import "Firestore/Source/Util/FSTAssert.h"
-#import "Firestore/Source/Util/FSTLogger.h"
 
 #import "Firestore/Example/Tests/Core/FSTSyncEngine+Testing.h"
 #import "Firestore/Example/Tests/SpecTests/FSTMockDatastore.h"
@@ -41,6 +40,7 @@
 #include "Firestore/core/src/firebase/firestore/core/database_info.h"
 #include "Firestore/core/src/firebase/firestore/model/database_id.h"
 #include "Firestore/core/src/firebase/firestore/model/document_key.h"
+#include "Firestore/core/src/firebase/firestore/util/log.h"
 
 using firebase::firestore::auth::EmptyCredentialsProvider;
 using firebase::firestore::auth::HashUser;
@@ -202,7 +202,7 @@ NS_ASSUME_NONNULL_BEGIN
   FSTAssert([actualWrite isEqual:expectedWrite],
             @"Mock datastore received write %@ but first outstanding mutation was %@", actualWrite,
             expectedWrite);
-  FSTLog(@"A write was sent: %@", actualWrite);
+  LOG_DEBUG("A write was sent: %s", actualWrite);
 }
 
 - (int)sentWritesCount {
@@ -271,7 +271,7 @@ NS_ASSUME_NONNULL_BEGIN
     [[self currentOutstandingWrites] removeObjectAtIndex:0];
   }
 
-  FSTLog(@"Failing a write.");
+  LOG_DEBUG("Failing a write.");
   [self.dispatchQueue dispatchSync:^{
     [self.datastore failWriteWithError:error];
   }];
@@ -321,11 +321,11 @@ NS_ASSUME_NONNULL_BEGIN
   FSTOutstandingWrite *write = [[FSTOutstandingWrite alloc] init];
   write.write = mutation;
   [[self currentOutstandingWrites] addObject:write];
-  FSTLog(@"sending a user write.");
+  LOG_DEBUG("sending a user write.");
   [self.dispatchQueue dispatchSync:^{
     [self.syncEngine writeMutations:@[ mutation ]
                          completion:^(NSError *_Nullable error) {
-                           FSTLog(@"A callback was called with error: %@", error);
+                           LOG_DEBUG("A callback was called with error: %s", error);
                            write.done = YES;
                            write.error = error;
                          }];
diff --git a/Firestore/Source/API/FIRFirestore.mm b/Firestore/Source/API/FIRFirestore.mm
index 5486b75..0ed9082 100644
--- a/Firestore/Source/API/FIRFirestore.mm
+++ b/Firestore/Source/API/FIRFirestore.mm
@@ -34,7 +34,6 @@
 #import "Firestore/Source/Core/FSTFirestoreClient.h"
 #import "Firestore/Source/Util/FSTAssert.h"
 #import "Firestore/Source/Util/FSTDispatchQueue.h"
-#import "Firestore/Source/Util/FSTLogger.h"
 #import "Firestore/Source/Util/FSTUsageValidation.h"
 
 #include "Firestore/core/src/firebase/firestore/auth/credentials_provider.h"
@@ -42,6 +41,7 @@
 #include "Firestore/core/src/firebase/firestore/core/database_info.h"
 #include "Firestore/core/src/firebase/firestore/model/database_id.h"
 #include "Firestore/core/src/firebase/firestore/model/resource_path.h"
+#include "Firestore/core/src/firebase/firestore/util/log.h"
 #include "Firestore/core/src/firebase/firestore/util/string_apple.h"
 #include "absl/memory/memory.h"
 
@@ -246,31 +246,31 @@ extern "C" NSString *const FIRFirestoreErrorDomain = @"FIRFirestoreErrorDomain";
       FSTAssert(_settings.dispatchQueue, @"FirestoreSettings.dispatchQueue cannot be nil.");
 
       if (!_settings.timestampsInSnapshotsEnabled) {
-        FSTWarn(
-            @"The behavior for system Date objects stored in Firestore is going to change "
-             "AND YOUR APP MAY BREAK.\n"
-             "To hide this warning and ensure your app does not break, you need to add "
-             "the following code to your app before calling any other Cloud Firestore methods:\n"
-             "\n"
-             "let db = Firestore.firestore()\n"
-             "let settings = db.settings\n"
-             "settings.areTimestampsInSnapshotsEnabled = true\n"
-             "db.settings = settings\n"
-             "\n"
-             "With this change, timestamps stored in Cloud Firestore will be read back as "
-             "Firebase Timestamp objects instead of as system Date objects. So you will "
-             "also need to update code expecting a Date to instead expect a Timestamp. "
-             "For example:\n"
-             "\n"
-             "// old:\n"
-             "let date: Date = documentSnapshot.get(\"created_at\") as! Date\n"
-             "// new:\n"
-             "let timestamp: Timestamp = documentSnapshot.get(\"created_at\") as! Timestamp\n"
-             "let date: Date = timestamp.dateValue()\n"
-             "\n"
-             "Please audit all existing usages of Date when you enable the new behavior. In a "
-             "future release, the behavior will be changed to the new behavior, so if you do not "
-             "follow these steps, YOUR APP MAY BREAK.");
+        LOG_WARN(
+            "The behavior for system Date objects stored in Firestore is going to change "
+            "AND YOUR APP MAY BREAK.\n"
+            "To hide this warning and ensure your app does not break, you need to add "
+            "the following code to your app before calling any other Cloud Firestore methods:\n"
+            "\n"
+            "let db = Firestore.firestore()\n"
+            "let settings = db.settings\n"
+            "settings.areTimestampsInSnapshotsEnabled = true\n"
+            "db.settings = settings\n"
+            "\n"
+            "With this change, timestamps stored in Cloud Firestore will be read back as "
+            "Firebase Timestamp objects instead of as system Date objects. So you will "
+            "also need to update code expecting a Date to instead expect a Timestamp. "
+            "For example:\n"
+            "\n"
+            "// old:\n"
+            "let date: Date = documentSnapshot.get(\"created_at\") as! Date\n"
+            "// new:\n"
+            "let timestamp: Timestamp = documentSnapshot.get(\"created_at\") as! Timestamp\n"
+            "let date: Date = timestamp.dateValue()\n"
+            "\n"
+            "Please audit all existing usages of Date when you enable the new behavior. In a "
+            "future release, the behavior will be changed to the new behavior, so if you do not "
+            "follow these steps, YOUR APP MAY BREAK.");
       }
 
       const DatabaseInfo database_info(*self.databaseID, util::MakeStringView(_persistenceKey),
diff --git a/Firestore/Source/Core/FSTFirestoreClient.mm b/Firestore/Source/Core/FSTFirestoreClient.mm
index cede958..da19960 100644
--- a/Firestore/Source/Core/FSTFirestoreClient.mm
+++ b/Firestore/Source/Core/FSTFirestoreClient.mm
@@ -45,11 +45,11 @@
 #import "Firestore/Source/Util/FSTAssert.h"
 #import "Firestore/Source/Util/FSTClasses.h"
 #import "Firestore/Source/Util/FSTDispatchQueue.h"
-#import "Firestore/Source/Util/FSTLogger.h"
 
 #include "Firestore/core/src/firebase/firestore/auth/credentials_provider.h"
 #include "Firestore/core/src/firebase/firestore/core/database_info.h"
 #include "Firestore/core/src/firebase/firestore/model/database_id.h"
+#include "Firestore/core/src/firebase/firestore/util/log.h"
 #include "Firestore/core/src/firebase/firestore/util/string_apple.h"
 
 namespace util = firebase::firestore::util;
@@ -226,7 +226,7 @@ NS_ASSUME_NONNULL_BEGIN
 - (void)userDidChange:(const User &)user {
   [self.workerDispatchQueue verifyIsCurrentQueue];
 
-  FSTLog(@"User Changed: %s", user.uid().c_str());
+  LOG_DEBUG("User Changed: %s", user.uid());
   [self.syncEngine userDidChange:user];
 }
 
diff --git a/Firestore/Source/Core/FSTSyncEngine.mm b/Firestore/Source/Core/FSTSyncEngine.mm
index ed97d6c..9d9e526 100644
--- a/Firestore/Source/Core/FSTSyncEngine.mm
+++ b/Firestore/Source/Core/FSTSyncEngine.mm
@@ -40,12 +40,12 @@
 #import "Firestore/Source/Remote/FSTRemoteEvent.h"
 #import "Firestore/Source/Util/FSTAssert.h"
 #import "Firestore/Source/Util/FSTDispatchQueue.h"
-#import "Firestore/Source/Util/FSTLogger.h"
 
 #include "Firestore/core/src/firebase/firestore/auth/user.h"
 #include "Firestore/core/src/firebase/firestore/core/target_id_generator.h"
 #include "Firestore/core/src/firebase/firestore/model/document_key.h"
 #include "Firestore/core/src/firebase/firestore/model/snapshot_version.h"
+#include "Firestore/core/src/firebase/firestore/util/log.h"
 
 using firebase::firestore::auth::HashUser;
 using firebase::firestore::auth::User;
@@ -470,7 +470,7 @@ static const FSTListenSequenceNumber kIrrelevantSequenceNumber = -1;
         break;
 
       case FSTLimboDocumentChangeTypeRemoved:
-        FSTLog(@"Document no longer in limbo: %s", limboChange.key.ToString().c_str());
+        LOG_DEBUG("Document no longer in limbo: %s", limboChange.key.ToString());
         [self.limboDocumentRefs removeReferenceToKey:limboChange.key forID:targetID];
         break;
 
@@ -485,7 +485,7 @@ static const FSTListenSequenceNumber kIrrelevantSequenceNumber = -1;
   DocumentKey key{limboChange.key};
 
   if (_limboTargetsByKey.find(key) == _limboTargetsByKey.end()) {
-    FSTLog(@"New document in limbo: %s", key.ToString().c_str());
+    LOG_DEBUG("New document in limbo: %s", key.ToString());
     TargetId limboTargetID = _targetIdGenerator.NextId();
     FSTQuery *query = [FSTQuery queryWithPath:key.path()];
     FSTQueryData *queryData = [[FSTQueryData alloc] initWithQuery:query
diff --git a/Firestore/Source/Local/FSTLevelDB.mm b/Firestore/Source/Local/FSTLevelDB.mm
index bc2f2eb..6d0f8af 100644
--- a/Firestore/Source/Local/FSTLevelDB.mm
+++ b/Firestore/Source/Local/FSTLevelDB.mm
@@ -25,7 +25,6 @@
 #import "Firestore/Source/Local/FSTLevelDBRemoteDocumentCache.h"
 #import "Firestore/Source/Remote/FSTSerializerBeta.h"
 #import "Firestore/Source/Util/FSTAssert.h"
-#import "Firestore/Source/Util/FSTLogger.h"
 
 #include "Firestore/core/src/firebase/firestore/auth/user.h"
 #include "Firestore/core/src/firebase/firestore/core/database_info.h"
diff --git a/Firestore/Source/Local/FSTLocalStore.mm b/Firestore/Source/Local/FSTLocalStore.mm
index 0d6a785..245dd62 100644
--- a/Firestore/Source/Local/FSTLocalStore.mm
+++ b/Firestore/Source/Local/FSTLocalStore.mm
@@ -37,12 +37,12 @@
 #import "Firestore/Source/Model/FSTMutationBatch.h"
 #import "Firestore/Source/Remote/FSTRemoteEvent.h"
 #import "Firestore/Source/Util/FSTAssert.h"
-#import "Firestore/Source/Util/FSTLogger.h"
 
 #include "Firestore/core/src/firebase/firestore/auth/user.h"
 #include "Firestore/core/src/firebase/firestore/core/target_id_generator.h"
 #include "Firestore/core/src/firebase/firestore/model/document_key.h"
 #include "Firestore/core/src/firebase/firestore/model/snapshot_version.h"
+#include "Firestore/core/src/firebase/firestore/util/log.h"
 
 using firebase::firestore::auth::User;
 using firebase::firestore::core::TargetIdGenerator;
@@ -324,11 +324,11 @@ NS_ASSUME_NONNULL_BEGIN
           SnapshotVersion{doc.version} >= SnapshotVersion{existingDoc.version}) {
         [self.remoteDocumentCache addEntry:doc];
       } else {
-        FSTLog(
-            @"FSTLocalStore Ignoring outdated watch update for %s. "
-             "Current version: %s  Watch version: %s",
-            key.ToString().c_str(), existingDoc.version.timestamp().ToString().c_str(),
-            doc.version.timestamp().ToString().c_str());
+        LOG_DEBUG(
+            "FSTLocalStore Ignoring outdated watch update for %s. "
+            "Current version: %s  Watch version: %s",
+            key.ToString(), existingDoc.version.timestamp().ToString(),
+            doc.version.timestamp().ToString());
       }
 
       // The document might be garbage because it was unreferenced by everything.
diff --git a/Firestore/Source/Remote/FSTDatastore.mm b/Firestore/Source/Remote/FSTDatastore.mm
index f0852fe..d45af6b 100644
--- a/Firestore/Source/Remote/FSTDatastore.mm
+++ b/Firestore/Source/Remote/FSTDatastore.mm
@@ -33,7 +33,6 @@
 #import "Firestore/Source/Remote/FSTStream.h"
 #import "Firestore/Source/Util/FSTAssert.h"
 #import "Firestore/Source/Util/FSTDispatchQueue.h"
-#import "Firestore/Source/Util/FSTLogger.h"
 
 #import "Firestore/Protos/objc/google/firestore/v1beta1/Firestore.pbrpc.h"
 
@@ -43,6 +42,7 @@
 #include "Firestore/core/src/firebase/firestore/model/database_id.h"
 #include "Firestore/core/src/firebase/firestore/model/document_key.h"
 #include "Firestore/core/src/firebase/firestore/util/error_apple.h"
+#include "Firestore/core/src/firebase/firestore/util/log.h"
 #include "Firestore/core/src/firebase/firestore/util/string_apple.h"
 
 namespace util = firebase::firestore::util;
@@ -217,8 +217,8 @@ typedef GRPCProtoCall * (^RPCFactory)(void);
 /** Logs the (whitelisted) headers returned for an GRPCProtoCall RPC. */
 + (void)logHeadersForRPC:(GRPCProtoCall *)rpc RPCName:(NSString *)rpcName {
   if ([FIRFirestore isLoggingEnabled]) {
-    FSTLog(@"RPC %@ returned headers (whitelisted): %@", rpcName,
-           [FSTDatastore extractWhiteListedHeaders:rpc.responseHeaders]);
+    LOG_DEBUG("RPC %s returned headers (whitelisted): %s", rpcName,
+              [FSTDatastore extractWhiteListedHeaders:rpc.responseHeaders]);
   }
 }
 
@@ -239,7 +239,7 @@ typedef GRPCProtoCall * (^RPCFactory)(void);
                        handler:^(GCFSCommitResponse *response, NSError *_Nullable error) {
                          error = [FSTDatastore firestoreErrorForError:error];
                          [self.workerDispatchQueue dispatchAsync:^{
-                           FSTLog(@"RPC CommitRequest completed. Error: %@", error);
+                           LOG_DEBUG("RPC CommitRequest completed. Error: %s", error);
                            [FSTDatastore logHeadersForRPC:rpc RPCName:@"CommitRequest"];
                            completion(error);
                          }];
@@ -272,7 +272,7 @@ typedef GRPCProtoCall * (^RPCFactory)(void);
                                error = [FSTDatastore firestoreErrorForError:error];
                                [self.workerDispatchQueue dispatchAsync:^{
                                  if (error) {
-                                   FSTLog(@"RPC BatchGetDocuments completed. Error: %@", error);
+                                   LOG_DEBUG("RPC BatchGetDocuments completed. Error: %s", error);
                                    [FSTDatastore logHeadersForRPC:rpc RPCName:@"BatchGetDocuments"];
                                    completion(nil, error);
                                    return;
@@ -285,7 +285,7 @@ typedef GRPCProtoCall * (^RPCFactory)(void);
                                    closure->results.insert({doc.key, doc});
                                  } else {
                                    // Streaming response is done, call completion
-                                   FSTLog(@"RPC BatchGetDocuments completed successfully.");
+                                   LOG_DEBUG("RPC BatchGetDocuments completed successfully.");
                                    [FSTDatastore logHeadersForRPC:rpc RPCName:@"BatchGetDocuments"];
                                    FSTAssert(!response, @"Got response after done.");
                                    NSMutableArray<FSTMaybeDocument *> *docs =
diff --git a/Firestore/Source/Remote/FSTExponentialBackoff.mm b/Firestore/Source/Remote/FSTExponentialBackoff.mm
index 20b50a5..2bddbf7 100644
--- a/Firestore/Source/Remote/FSTExponentialBackoff.mm
+++ b/Firestore/Source/Remote/FSTExponentialBackoff.mm
@@ -18,10 +18,10 @@
 
 #include <random>
 
-#include "Firestore/core/src/firebase/firestore/util/secure_random.h"
-
 #import "Firestore/Source/Util/FSTDispatchQueue.h"
-#import "Firestore/Source/Util/FSTLogger.h"
+
+#include "Firestore/core/src/firebase/firestore/util/log.h"
+#include "Firestore/core/src/firebase/firestore/util/secure_random.h"
 
 using firebase::firestore::util::SecureRandom;
 
@@ -71,8 +71,7 @@ using firebase::firestore::util::SecureRandom;
   // First schedule the block using the current base (which may be 0 and should be honored as such).
   NSTimeInterval delayWithJitter = _currentBase + [self jitterDelay];
   if (_currentBase > 0) {
-    FSTLog(@"Backing off for %.2f seconds (base delay: %.2f seconds)", delayWithJitter,
-           _currentBase);
+    LOG_DEBUG("Backing off for %s seconds (base delay: %s seconds)", delayWithJitter, _currentBase);
   }
 
   self.timerCallback =
diff --git a/Firestore/Source/Remote/FSTOnlineStateTracker.mm b/Firestore/Source/Remote/FSTOnlineStateTracker.mm
index e782397..e512a3c 100644
--- a/Firestore/Source/Remote/FSTOnlineStateTracker.mm
+++ b/Firestore/Source/Remote/FSTOnlineStateTracker.mm
@@ -18,7 +18,8 @@
 #import "Firestore/Source/Remote/FSTRemoteStore.h"
 #import "Firestore/Source/Util/FSTAssert.h"
 #import "Firestore/Source/Util/FSTDispatchQueue.h"
-#import "Firestore/Source/Util/FSTLogger.h"
+
+#include "Firestore/core/src/firebase/firestore/util/log.h"
 
 NS_ASSUME_NONNULL_BEGIN
 
@@ -83,10 +84,9 @@ static const NSTimeInterval kOnlineStateTimeout = 10;
                        FSTAssert(
                            self.state == FSTOnlineStateUnknown,
                            @"Timer should be canceled if we transitioned to a different state.");
-                       FSTLog(
-                           @"Watch stream didn't reach Online or Offline within %f seconds. "
-                           @"Considering "
-                            "client offline.",
+                       LOG_DEBUG(
+                           "Watch stream didn't reach Online or Offline within %s seconds. "
+                           "Considering client offline.",
                            kOnlineStateTimeout);
                        [self logClientOfflineWarningIfNecessary];
                        [self setAndBroadcastState:FSTOnlineStateOffline];
@@ -138,7 +138,7 @@ static const NSTimeInterval kOnlineStateTimeout = 10;
 
 - (void)logClientOfflineWarningIfNecessary {
   if (self.shouldWarnClientIsOffline) {
-    FSTWarn(@"Could not reach Firestore backend.");
+    LOG_WARN("Could not reach Firestore backend.");
     self.shouldWarnClientIsOffline = NO;
   }
 }
diff --git a/Firestore/Source/Remote/FSTRemoteEvent.mm b/Firestore/Source/Remote/FSTRemoteEvent.mm
index 438072e..ebd9b93 100644
--- a/Firestore/Source/Remote/FSTRemoteEvent.mm
+++ b/Firestore/Source/Remote/FSTRemoteEvent.mm
@@ -24,9 +24,10 @@
 #import "Firestore/Source/Remote/FSTWatchChange.h"
 #import "Firestore/Source/Util/FSTAssert.h"
 #import "Firestore/Source/Util/FSTClasses.h"
-#import "Firestore/Source/Util/FSTLogger.h"
+
 #include "Firestore/core/src/firebase/firestore/model/document_key.h"
 #include "Firestore/core/src/firebase/firestore/util/hashing.h"
+#include "Firestore/core/src/firebase/firestore/util/log.h"
 
 using firebase::firestore::model::DocumentKey;
 using firebase::firestore::model::SnapshotVersion;
@@ -577,7 +578,7 @@ initWithSnapshotVersion:(SnapshotVersion)snapshotVersion
         }
         break;
       default:
-        FSTWarn(@"Unknown target watch change type: %ld", (long)targetChange.state);
+        LOG_WARN("Unknown target watch change type: %s", targetChange.state);
     }
   }
 }
diff --git a/Firestore/Source/Remote/FSTRemoteStore.mm b/Firestore/Source/Remote/FSTRemoteStore.mm
index 0ea4887..e0adb4e 100644
--- a/Firestore/Source/Remote/FSTRemoteStore.mm
+++ b/Firestore/Source/Remote/FSTRemoteStore.mm
@@ -32,11 +32,11 @@
 #import "Firestore/Source/Remote/FSTStream.h"
 #import "Firestore/Source/Remote/FSTWatchChange.h"
 #import "Firestore/Source/Util/FSTAssert.h"
-#import "Firestore/Source/Util/FSTLogger.h"
 
 #include "Firestore/core/src/firebase/firestore/auth/user.h"
 #include "Firestore/core/src/firebase/firestore/model/document_key.h"
 #include "Firestore/core/src/firebase/firestore/model/snapshot_version.h"
+#include "Firestore/core/src/firebase/firestore/util/log.h"
 #include "Firestore/core/src/firebase/firestore/util/string_apple.h"
 
 namespace util = firebase::firestore::util;
@@ -205,7 +205,7 @@ static const int kMaxPendingWrites = 10;
 #pragma mark Shutdown
 
 - (void)shutdown {
-  FSTLog(@"FSTRemoteStore %p shutting down", (__bridge void *)self);
+  LOG_DEBUG("FSTRemoteStore %s shutting down", (__bridge void *)self);
   [self disableNetworkInternal];
   // Set the FSTOnlineState to Unknown (rather than Offline) to avoid potentially triggering
   // spurious listener events with cached data, etc.
@@ -213,7 +213,7 @@ static const int kMaxPendingWrites = 10;
 }
 
 - (void)userDidChange:(const User &)user {
-  FSTLog(@"FSTRemoteStore %p changing users: %s", (__bridge void *)self, user.uid().c_str());
+  LOG_DEBUG("FSTRemoteStore %s changing users: %s", (__bridge void *)self, user.uid());
   if ([self isNetworkEnabled]) {
     // Tear down and re-create our network streams. This will ensure we get a fresh auth token
     // for the new user and re-fill the write pipeline with new mutations from the LocalStore
@@ -408,7 +408,7 @@ static const int kMaxPendingWrites = 10;
       }
 
       if (trackedRemote.size() != static_cast<size_t>(filter.count)) {
-        FSTLog(@"Existence filter mismatch, resetting mapping");
+        LOG_DEBUG("Existence filter mismatch, resetting mapping");
 
         // Make sure the mismatch is exposed in the remote event
         [remoteEvent handleExistenceFilterMismatchForTargetID:target];
@@ -490,8 +490,7 @@ static const int kMaxPendingWrites = 10;
 
 - (void)cleanUpWriteStreamState {
   self.lastBatchSeen = kFSTBatchIDUnknown;
-  FSTLog(@"Stopping write stream with %lu pending writes",
-         (unsigned long)[self.pendingWrites count]);
+  LOG_DEBUG("Stopping write stream with %s pending writes", [self.pendingWrites count]);
   [self.pendingWrites removeAllObjects];
 }
 
@@ -618,8 +617,8 @@ static const int kMaxPendingWrites = 10;
   // stream is no longer valid.
   if ([FSTDatastore isPermanentWriteError:error] || [FSTDatastore isAbortedError:error]) {
     NSString *token = [self.writeStream.lastStreamToken base64EncodedStringWithOptions:0];
-    FSTLog(@"FSTRemoteStore %p error before completed handshake; resetting stream token %@: %@",
-           (__bridge void *)self, token, error);
+    LOG_DEBUG("FSTRemoteStore %s error before completed handshake; resetting stream token %s: %s",
+              (__bridge void *)self, token, error);
     self.writeStream.lastStreamToken = nil;
     [self.localStore setLastStreamToken:nil];
   }
diff --git a/Firestore/Source/Remote/FSTStream.mm b/Firestore/Source/Remote/FSTStream.mm
index f4ec675..0e45418 100644
--- a/Firestore/Source/Remote/FSTStream.mm
+++ b/Firestore/Source/Remote/FSTStream.mm
@@ -29,7 +29,6 @@
 #import "Firestore/Source/Util/FSTAssert.h"
 #import "Firestore/Source/Util/FSTClasses.h"
 #import "Firestore/Source/Util/FSTDispatchQueue.h"
-#import "Firestore/Source/Util/FSTLogger.h"
 
 #import "Firestore/Protos/objc/google/firestore/v1beta1/Firestore.pbrpc.h"
 
@@ -38,6 +37,7 @@
 #include "Firestore/core/src/firebase/firestore/model/database_id.h"
 #include "Firestore/core/src/firebase/firestore/model/snapshot_version.h"
 #include "Firestore/core/src/firebase/firestore/util/error_apple.h"
+#include "Firestore/core/src/firebase/firestore/util/log.h"
 #include "Firestore/core/src/firebase/firestore/util/string_apple.h"
 
 namespace util = firebase::firestore::util;
@@ -258,7 +258,7 @@ static const NSTimeInterval kIdleTimeout = 60.0;
     return;
   }
 
-  FSTLog(@"%@ %p start", NSStringFromClass([self class]), (__bridge void *)self);
+  LOG_DEBUG("%s %s start", NSStringFromClass([self class]), (__bridge void *)self);
   FSTAssert(self.state == FSTStreamStateInitial, @"Already started");
 
   self.state = FSTStreamStateAuth;
@@ -311,7 +311,7 @@ static const NSTimeInterval kIdleTimeout = 60.0;
 
 /** Backs off after an error. */
 - (void)performBackoffWithDelegate:(id)delegate {
-  FSTLog(@"%@ %p backoff", NSStringFromClass([self class]), (__bridge void *)self);
+  LOG_DEBUG("%s %s backoff", NSStringFromClass([self class]), (__bridge void *)self);
   [self.workerDispatchQueue verifyIsCurrentQueue];
 
   FSTAssert(self.state == FSTStreamStateError, @"Should only perform backoff in an error case");
@@ -381,13 +381,13 @@ static const NSTimeInterval kIdleTimeout = 60.0;
     // If this is an intentional close ensure we don't delay our next connection attempt.
     [self.backoff reset];
   } else if (error != nil && error.code == FIRFirestoreErrorCodeResourceExhausted) {
-    FSTLog(@"%@ %p Using maximum backoff delay to prevent overloading the backend.", [self class],
-           (__bridge void *)self);
+    LOG_DEBUG("%s %s Using maximum backoff delay to prevent overloading the backend.", [self class],
+              (__bridge void *)self);
     [self.backoff resetToMax];
   }
 
   if (finalState != FSTStreamStateError) {
-    FSTLog(@"%@ %p Performing stream teardown", [self class], (__bridge void *)self);
+    LOG_DEBUG("%s %s Performing stream teardown", [self class], (__bridge void *)self);
     [self tearDown];
   }
 
@@ -395,7 +395,7 @@ static const NSTimeInterval kIdleTimeout = 60.0;
     // Clean up the underlying RPC. If this close: is in response to an error, don't attempt to
     // call half-close to avoid secondary failures.
     if (finalState != FSTStreamStateError) {
-      FSTLog(@"%@ %p Closing stream client-side", [self class], (__bridge void *)self);
+      LOG_DEBUG("%s %s Closing stream client-side", [self class], (__bridge void *)self);
       @synchronized(self.requestsWriter) {
         [self.requestsWriter finishWithError:nil];
       }
@@ -426,7 +426,7 @@ static const NSTimeInterval kIdleTimeout = 60.0;
 }
 
 - (void)stop {
-  FSTLog(@"%@ %p stop", NSStringFromClass([self class]), (__bridge void *)self);
+  LOG_DEBUG("%s %s stop", NSStringFromClass([self class]), (__bridge void *)self);
   if ([self isStarted]) {
     [self closeWithFinalState:FSTStreamStateStopped error:nil];
   }
@@ -550,7 +550,7 @@ static const NSTimeInterval kIdleTimeout = 60.0;
  * Called by the stream when the underlying RPC has been closed for whatever reason.
  */
 - (void)handleStreamClose:(nullable NSError *)error {
-  FSTLog(@"%@ %p close: %@", NSStringFromClass([self class]), (__bridge void *)self, error);
+  LOG_DEBUG("%s %s close: %s", NSStringFromClass([self class]), (__bridge void *)self, error);
   FSTAssert([self isStarted], @"handleStreamClose: called for non-started stream.");
 
   // In theory the stream could close cleanly, however, in our current model we never expect this
@@ -577,9 +577,9 @@ static const NSTimeInterval kIdleTimeout = 60.0;
     if (!self.messageReceived) {
       self.messageReceived = YES;
       if ([FIRFirestore isLoggingEnabled]) {
-        FSTLog(@"%@ %p headers (whitelisted): %@", NSStringFromClass([self class]),
-               (__bridge void *)self,
-               [FSTDatastore extractWhiteListedHeaders:self.rpc.responseHeaders]);
+        LOG_DEBUG("%s %s headers (whitelisted): %s", NSStringFromClass([self class]),
+                  (__bridge void *)self,
+                  [FSTDatastore extractWhiteListedHeaders:self.rpc.responseHeaders]);
       }
     }
     NSError *error;
@@ -665,7 +665,7 @@ static const NSTimeInterval kIdleTimeout = 60.0;
   request.addTarget = [_serializer encodedTarget:query];
   request.labels = [_serializer encodedListenRequestLabelsForQueryData:query];
 
-  FSTLog(@"FSTWatchStream %p watch: %@", (__bridge void *)self, request);
+  LOG_DEBUG("FSTWatchStream %s watch: %s", (__bridge void *)self, request);
   [self writeRequest:request];
 }
 
@@ -677,7 +677,7 @@ static const NSTimeInterval kIdleTimeout = 60.0;
   request.database = [_serializer encodedDatabaseID];
   request.removeTarget = targetID;
 
-  FSTLog(@"FSTWatchStream %p unwatch: %@", (__bridge void *)self, request);
+  LOG_DEBUG("FSTWatchStream %s unwatch: %s", (__bridge void *)self, request);
   [self writeRequest:request];
 }
 
@@ -686,7 +686,7 @@ static const NSTimeInterval kIdleTimeout = 60.0;
  * watchStreamDidChange:snapshotVersion: callback.
  */
 - (void)handleStreamMessage:(GCFSListenResponse *)proto {
-  FSTLog(@"FSTWatchStream %p response: %@", (__bridge void *)self, proto);
+  LOG_DEBUG("FSTWatchStream %s response: %s", (__bridge void *)self, proto);
   [self.workerDispatchQueue verifyIsCurrentQueue];
 
   // A successful response means the stream is healthy.
@@ -765,7 +765,7 @@ static const NSTimeInterval kIdleTimeout = 60.0;
   // TODO(dimond): Support stream resumption. We intentionally do not set the stream token on the
   // handshake, ignoring any stream token we might have.
 
-  FSTLog(@"FSTWriteStream %p initial request: %@", (__bridge void *)self, request);
+  LOG_DEBUG("FSTWriteStream %s initial request: %s", (__bridge void *)self, request);
   [self writeRequest:request];
 }
 
@@ -783,7 +783,7 @@ static const NSTimeInterval kIdleTimeout = 60.0;
   request.writesArray = protos;
   request.streamToken = self.lastStreamToken;
 
-  FSTLog(@"FSTWriteStream %p mutation request: %@", (__bridge void *)self, request);
+  LOG_DEBUG("FSTWriteStream %s mutation request: %s", (__bridge void *)self, request);
   [self writeRequest:request];
 }
 
@@ -792,7 +792,7 @@ static const NSTimeInterval kIdleTimeout = 60.0;
  * that on to the mutationResultsHandler.
  */
 - (void)handleStreamMessage:(GCFSWriteResponse *)response {
-  FSTLog(@"FSTWriteStream %p response: %@", (__bridge void *)self, response);
+  LOG_DEBUG("FSTWriteStream %s response: %s", (__bridge void *)self, response);
   [self.workerDispatchQueue verifyIsCurrentQueue];
 
   // Always capture the last stream token.
diff --git a/Firestore/Source/Util/FSTLogger.h b/Firestore/Source/Util/FSTLogger.h
deleted file mode 100644
index c4e2b85..0000000
--- a/Firestore/Source/Util/FSTLogger.h
+++ /dev/null
@@ -1,26 +0,0 @@
-/*
- * Copyright 2017 Google
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#import <Foundation/Foundation.h>
-
-NS_ASSUME_NONNULL_BEGIN
-
-/** Logs to NSLog if [FIRFirestore isLoggingEnabled] is YES. */
-void FSTLog(NSString *format, ...) NS_FORMAT_FUNCTION(1, 2);
-
-void FSTWarn(NSString *format, ...) NS_FORMAT_FUNCTION(1, 2);
-
-NS_ASSUME_NONNULL_END
diff --git a/Firestore/Source/Util/FSTLogger.mm b/Firestore/Source/Util/FSTLogger.mm
deleted file mode 100644
index f0081e0..0000000
--- a/Firestore/Source/Util/FSTLogger.mm
+++ /dev/null
@@ -1,41 +0,0 @@
-/*
- * Copyright 2017 Google
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#import "Firestore/Source/Util/FSTLogger.h"
-
-#import <FirebaseCore/FIRLogger.h>
-
-#import "Firestore/Source/API/FIRFirestore+Internal.h"
-
-NS_ASSUME_NONNULL_BEGIN
-
-void FSTLog(NSString *format, ...) {
-  if ([FIRFirestore isLoggingEnabled]) {
-    va_list args;
-    va_start(args, format);
-    FIRLogBasic(FIRLoggerLevelDebug, kFIRLoggerFirestore, @"I-FST000001", format, args);
-    va_end(args);
-  }
-}
-
-void FSTWarn(NSString *format, ...) {
-  va_list args;
-  va_start(args, format);
-  FIRLogBasic(FIRLoggerLevelWarning, kFIRLoggerFirestore, @"I-FST000001", format, args);
-  va_end(args);
-}
-
-NS_ASSUME_NONNULL_END
diff --git a/Firestore/core/src/firebase/firestore/local/leveldb_transaction.cc b/Firestore/core/src/firebase/firestore/local/leveldb_transaction.cc
index 3581ef5..da9f004 100644
--- a/Firestore/core/src/firebase/firestore/local/leveldb_transaction.cc
+++ b/Firestore/core/src/firebase/firestore/local/leveldb_transaction.cc
@@ -212,9 +212,7 @@ void LevelDbTransaction::Commit() {
     batch.Put(it->first, it->second);
   }
 
-  if (util::LogGetLevel() <= util::kLogLevelDebug) {
-    util::LogDebug("Committing transaction: %s", ToString().c_str());
-  }
+  LOG_DEBUG("Committing transaction: %s", ToString());
 
   Status status = db_->Write(write_options_, &batch);
   HARD_ASSERT(status.ok(), "Failed to commit transaction:\n%s\n Failed: %s",
diff --git a/Firestore/core/src/firebase/firestore/util/log.h b/Firestore/core/src/firebase/firestore/util/log.h
index 1944596..248d434 100644
--- a/Firestore/core/src/firebase/firestore/util/log.h
+++ b/Firestore/core/src/firebase/firestore/util/log.h
@@ -17,44 +17,65 @@
 #ifndef FIRESTORE_CORE_SRC_FIREBASE_FIRESTORE_UTIL_LOG_H_
 #define FIRESTORE_CORE_SRC_FIREBASE_FIRESTORE_UTIL_LOG_H_
 
-#include <cstdarg>
+#include <string>
+
+#include "Firestore/core/src/firebase/firestore/util/string_format.h"
 
 namespace firebase {
 namespace firestore {
 namespace util {
 
-/// @brief Levels used when logging messages.
+// Levels used when logging messages.
 enum LogLevel {
-  /// Verbose Log Level
-  kLogLevelVerbose = 0,
-  /// Debug Log Level
+  // Debug Log Level
   kLogLevelDebug,
-  /// Info Log Level
-  kLogLevelInfo,
-  /// Warning Log Level
+  // Warning Log Level
   kLogLevelWarning,
-  /// Error Log Level
-  kLogLevelError,
 };
 
-// Common log methods.
+// Log a message if kLogLevelDebug is enabled. Arguments are not evaluated if
+// logging is disabled.
+//
+// @param format A format string suitable for use with `util::StringFormat`
+// @param ... C++ variadic arguments that match the format string. Not C
+//     varargs.
+#define LOG_DEBUG(...)                                         \
+  do {                                                         \
+    namespace _util = firebase::firestore::util;               \
+    if (_util::LogIsLoggable(_util::kLogLevelDebug)) {         \
+      std::string _message = _util::StringFormat(__VA_ARGS__); \
+      _util::LogMessage(_util::kLogLevelDebug, _message);      \
+    }                                                          \
+  } while (0)
+
+// Log a message if kLogLevelWarn is enabled (it is by default). Arguments are
+// not evaluated if logging is disabled.
+//
+// @param format A format string suitable for use with `util::StringFormat`
+// @param ... C++ variadic arguments that match the format string. Not C
+//     varargs.
+#define LOG_WARN(...)                                          \
+  do {                                                         \
+    namespace _util = firebase::firestore::util;               \
+    if (_util::LogIsLoggable(_util::kLogLevelWarning)) {       \
+      std::string _message = _util::StringFormat(__VA_ARGS__); \
+      _util::LogMessage(_util::kLogLevelWarning, _message);    \
+    }                                                          \
+  } while (0)
+
+// Tests to see if the given log level is loggable.
+bool LogIsLoggable(LogLevel level);
+
+// Is debug logging enabled?
+inline bool LogIsDebugEnabled() {
+  return LogIsLoggable(kLogLevelDebug);
+}
 
 // All messages at or above the specified log level value are displayed.
 void LogSetLevel(LogLevel level);
-// Get the currently set log level.
-LogLevel LogGetLevel();
-// Log a debug message to the system log.
-void LogDebug(const char* format, ...);
-// Log an info message to the system log.
-void LogInfo(const char* format, ...);
-// Log a warning to the system log.
-void LogWarning(const char* format, ...);
-// Log an error to the system log.
-void LogError(const char* format, ...);
-// Log a firebase message (implemented by the platform specific logger).
-void LogMessageV(LogLevel log_level, const char* format, va_list args);
-// Log a firebase message via LogMessageV().
-void LogMessage(LogLevel log_level, const char* format, ...);
+
+// Log a message at the given level.
+void LogMessage(LogLevel log_level, const std::string& message);
 
 }  // namespace util
 }  // namespace firestore
diff --git a/Firestore/core/src/firebase/firestore/util/log_apple.mm b/Firestore/core/src/firebase/firestore/util/log_apple.mm
index cb2c58e..45e4f55 100644
--- a/Firestore/core/src/firebase/firestore/util/log_apple.mm
+++ b/Firestore/core/src/firebase/firestore/util/log_apple.mm
@@ -19,6 +19,7 @@
 #import <FirebaseCore/FIRLogger.h>
 #import <Foundation/Foundation.h>
 
+#include <cstdarg>
 #include <string>
 
 #include "Firestore/core/src/firebase/firestore/util/string_apple.h"
@@ -32,90 +33,40 @@ namespace {
 // Translates a C++ LogLevel to the equivalent Objective-C FIRLoggerLevel
 FIRLoggerLevel ToFIRLoggerLevel(LogLevel level) {
   switch (level) {
-    case kLogLevelVerbose:  // fall through
     case kLogLevelDebug:
       return FIRLoggerLevelDebug;
-    case kLogLevelInfo:
-      return FIRLoggerLevelInfo;
     case kLogLevelWarning:
       return FIRLoggerLevelWarning;
-    case kLogLevelError:
-      return FIRLoggerLevelError;
     default:
       // Unsupported log level. FIRSetLoggerLevel will deal with it.
       return static_cast<FIRLoggerLevel>(-1);
   }
 }
 
-}  // namespace
-
-void LogSetLevel(LogLevel level) {
-  FIRSetLoggerLevel(ToFIRLoggerLevel(level));
-}
-
-LogLevel LogGetLevel() {
-  // We return the true log level. True log level is what the SDK used to
-  // determine whether to log instead of what parameter is used in the last call
-  // of LogSetLevel().
-  if (FIRIsLoggableLevel(FIRLoggerLevelInfo, NO)) {
-    if (FIRIsLoggableLevel(FIRLoggerLevelDebug, NO)) {
-      // FIRLoggerLevelMax is actually kLogLevelDebug right now. We do not check
-      // further.
-      return kLogLevelDebug;
-    } else {
-      return kLogLevelInfo;
-    }
-  } else {
-    if (FIRIsLoggableLevel(FIRLoggerLevelWarning, NO)) {
-      return kLogLevelWarning;
-    } else {
-      return kLogLevelError;
-    }
-  }
-}
-
-void LogDebug(const char* format, ...) {
+// Actually logs a message via FIRLogger. This must be a C varargs function
+// so that we can call FIRLogBasic which takes a `va_list`.
+void LogMessageV(LogLevel level, NSString* format, ...) {
   va_list list;
   va_start(list, format);
-  FIRLogBasic(FIRLoggerLevelDebug, kFIRLoggerFirestore, @"I-FST000001",
-              WrapNSStringNoCopy(format), list);
-  va_end(list);
-}
 
-void LogInfo(const char* format, ...) {
-  va_list list;
-  va_start(list, format);
-  FIRLogBasic(FIRLoggerLevelInfo, kFIRLoggerFirestore, @"I-FST000001",
-              WrapNSStringNoCopy(format), list);
-  va_end(list);
-}
+  FIRLogBasic(ToFIRLoggerLevel(level), kFIRLoggerFirestore, @"I-FST000001",
+              format, list);
 
-void LogWarning(const char* format, ...) {
-  va_list list;
-  va_start(list, format);
-  FIRLogBasic(FIRLoggerLevelWarning, kFIRLoggerFirestore, @"I-FST000001",
-              WrapNSStringNoCopy(format), list);
   va_end(list);
 }
 
-void LogError(const char* format, ...) {
-  va_list list;
-  va_start(list, format);
-  FIRLogBasic(FIRLoggerLevelError, kFIRLoggerFirestore, @"I-FST000001",
-              WrapNSStringNoCopy(format), list);
-  va_end(list);
+}  // namespace
+
+void LogSetLevel(LogLevel level) {
+  FIRSetLoggerLevel(ToFIRLoggerLevel(level));
 }
 
-void LogMessageV(LogLevel log_level, const char* format, va_list args) {
-  FIRLogBasic(ToFIRLoggerLevel(log_level), kFIRLoggerFirestore, @"I-FST000001",
-              WrapNSStringNoCopy(format), args);
+bool LogIsLoggable(LogLevel level) {
+  return FIRIsLoggableLevel(ToFIRLoggerLevel(level), NO);
 }
 
-void LogMessage(LogLevel log_level, const char* format, ...) {
-  va_list list;
-  va_start(list, format);
-  LogMessageV(log_level, format, list);
-  va_end(list);
+void LogMessage(LogLevel level, const std::string& message) {
+  LogMessageV(level, @"%s", message.c_str());
 }
 
 }  // namespace util
diff --git a/Firestore/core/src/firebase/firestore/util/log_stdio.cc b/Firestore/core/src/firebase/firestore/util/log_stdio.cc
index b277406..6fff885 100644
--- a/Firestore/core/src/firebase/firestore/util/log_stdio.cc
+++ b/Firestore/core/src/firebase/firestore/util/log_stdio.cc
@@ -19,77 +19,42 @@
 #include <cstdio>
 #include <string>
 
+#include "Firestore/core/src/firebase/firestore/util/hard_assert.h"
+
 namespace firebase {
 namespace firestore {
 namespace util {
 
-LogLevel g_log_level = kLogLevelInfo;
+LogLevel g_log_level = kLogLevelWarning;
 
 void LogSetLevel(LogLevel level) {
   g_log_level = level;
 }
 
-LogLevel LogGetLevel() {
-  return g_log_level;
-}
-
-void LogDebug(const char* format, ...) {
-  va_list list;
-  va_start(list, format);
-  LogMessageV(kLogLevelDebug, format, list);
-  va_end(list);
-}
-
-void LogInfo(const char* format, ...) {
-  va_list list;
-  va_start(list, format);
-  LogMessageV(kLogLevelInfo, format, list);
-  va_end(list);
-}
-
-void LogWarning(const char* format, ...) {
-  va_list list;
-  va_start(list, format);
-  LogMessageV(kLogLevelWarning, format, list);
-  va_end(list);
+bool LogIsLoggable(LogLevel level) {
+  return level >= g_log_level;
 }
 
-void LogError(const char* format, ...) {
-  va_list list;
-  va_start(list, format);
-  LogMessageV(kLogLevelError, format, list);
-  va_end(list);
-}
-
-void LogMessageV(LogLevel log_level, const char* format, va_list args) {
+void LogMessage(LogLevel log_level, const std::string& message) {
   if (log_level < g_log_level) {
     return;
   }
+
+  const char* level_word;
+
   switch (log_level) {
-    case kLogLevelVerbose:
-      printf("VERBOSE: ");
-      break;
     case kLogLevelDebug:
-      printf("DEBUG: ");
-      break;
-    case kLogLevelInfo:
+      level_word = "DEBUG";
       break;
     case kLogLevelWarning:
-      printf("WARNING: ");
+      level_word = "WARNING";
       break;
-    case kLogLevelError:
-      printf("ERROR: ");
+    default:
+      UNREACHABLE();
       break;
   }
-  vprintf(format, args);
-  printf("\n");
-}
 
-void LogMessage(LogLevel log_level, const char* format, ...) {
-  va_list list;
-  va_start(list, format);
-  LogMessageV(log_level, format, list);
-  va_end(list);
+  printf("%s: %s\n", level_word, message.c_str());
 }
 
 }  // namespace util
diff --git a/Firestore/core/src/firebase/firestore/util/string_format.h b/Firestore/core/src/firebase/firestore/util/string_format.h
index 3d7a1dc..f8da785 100644
--- a/Firestore/core/src/firebase/firestore/util/string_format.h
+++ b/Firestore/core/src/firebase/firestore/util/string_format.h
@@ -21,6 +21,7 @@
 #include <string>
 #include <utility>
 
+#include "Firestore/core/src/firebase/firestore/util/string_apple.h"
 #include "absl/base/attributes.h"
 #include "absl/strings/str_cat.h"
 #include "absl/strings/string_view.h"
@@ -66,6 +67,12 @@ class FormatArg : public absl::AlphaNum {
       : FormatArg{std::forward<T>(value), internal::FormatChoice<0>{}} {
   }
 
+#if __OBJC__
+  FormatArg(NSObject* object)  // NOLINT(runtime/explicit)
+      : AlphaNum{MakeStringView([object description])} {
+  }
+#endif
+
  private:
   /**
    * Creates a FormatArg from a boolean value, representing the string
diff --git a/Firestore/core/test/firebase/firestore/util/log_test.cc b/Firestore/core/test/firebase/firestore/util/log_test.cc
index 973b174..73050ea 100644
--- a/Firestore/core/test/firebase/firestore/util/log_test.cc
+++ b/Firestore/core/test/firebase/firestore/util/log_test.cc
@@ -33,27 +33,19 @@ namespace util {
 //   defaults write firebase_firestore_util_log_apple_test
 //       /google/firebase/debug_mode NO
 TEST(Log, SetAndGet) {
-  LogSetLevel(kLogLevelVerbose);
+  EXPECT_FALSE(LogIsDebugEnabled());
 
   LogSetLevel(kLogLevelDebug);
-  EXPECT_EQ(kLogLevelDebug, LogGetLevel());
-
-  LogSetLevel(kLogLevelInfo);
-  EXPECT_EQ(kLogLevelInfo, LogGetLevel());
+  EXPECT_TRUE(LogIsDebugEnabled());
 
   LogSetLevel(kLogLevelWarning);
-  EXPECT_EQ(kLogLevelWarning, LogGetLevel());
-
-  LogSetLevel(kLogLevelError);
-  EXPECT_EQ(kLogLevelError, LogGetLevel());
+  EXPECT_FALSE(LogIsDebugEnabled());
 }
 
 TEST(Log, LogAllKinds) {
-  LogDebug("test debug logging %d", 1);
-  LogInfo("test info logging %d", 2);
-  LogWarning("test warning logging %d", 3);
-  LogError("test error logging %d", 4);
-  LogMessage(kLogLevelError, "test va-args %s %c %d", "abc", ':', 123);
+  LOG_DEBUG("test debug logging %s", 1);
+  LOG_WARN("test warning logging %s", 3);
+  LOG_DEBUG("test va-args %s %s %s", "abc", std::string{"def"}, 123);
 }
 
 }  //  namespace util