SERVER-18373 SERVER-18219 add MONGO_UNREACHABLE macro where compiler cannot deduce that WCE retry loops will return

3 files changed, 16 insertions, 0 deletions

diff --git a/src/mongo/db/repl/minvalid.cpp b/src/mongo/db/repl/minvalid.cpp
index ec39364ea13..f358ab59d05 100644
--- a/src/mongo/db/repl/minvalid.cpp
+++ b/src/mongo/db/repl/minvalid.cpp
@@ -81,6 +81,7 @@ bool getInitialSyncFlag() {
         return false;
     }
     MONGO_WRITE_CONFLICT_RETRY_LOOP_END(&txn, "getInitialSyncFlags", minvalidNS);
+    MONGO_UNREACHABLE;
 }
 
 void setMinValid(OperationContext* ctx, OpTime ts) {
diff --git a/src/mongo/db/repl/sync.cpp b/src/mongo/db/repl/sync.cpp
index d77827bc57c..85fde74d5fc 100644
--- a/src/mongo/db/repl/sync.cpp
+++ b/src/mongo/db/repl/sync.cpp
@@ -144,6 +144,7 @@ bool Sync::shouldRetry(OperationContext* txn, const BSONObj& o) {
         }
     }
     MONGO_WRITE_CONFLICT_RETRY_LOOP_END(txn, "InsertRetry", nss.ns());
+    MONGO_UNREACHABLE;
 }
 
 }  // namespace repl
diff --git a/src/mongo/util/assert_util.h b/src/mongo/util/assert_util.h
index 4a932db33f9..abff9afcace 100644
--- a/src/mongo/util/assert_util.h
+++ b/src/mongo/util/assert_util.h
@@ -401,3 +401,17 @@ std::string demangleName(const std::type_info& typeinfo);
                                           ::mongo::logger::LogSeverity::Log())                 \
             << "caught unknown exception in destructor (" << __FUNCTION__ << ")" << std::endl; \
     }
+
+/**
+ * The purpose of this macro is to instruct the compiler that a line of code will never be reached.
+ *
+ * Example:
+ *     // code above checks that expr can only be FOO or BAR
+ *     switch (expr) {
+ *     case FOO: { ... }
+ *     case BAR: { ... }
+ *     default:
+ *         MONGO_UNREACHABLE;
+ */
+
+#define MONGO_UNREACHABLE ::mongo::invariantFailed("Hit a MONGO_UNREACHABLE!", __FILE__, __LINE__);