refactor: ensure LDLogLevel is at least 32 bits wide (#415)

C++ compilers (specifically clang) complain that
`static_cast<LDLogLevel>(some_value_outside_range_of_defined_enum_values)`
is UB. To fix this, add a value to the enum forcing the valid range to
be 32 bits.

libs/common/include/launchdarkly/bindings/c/logging/log_level.h

@@ -8,6 +8,7 @@
 
 #include <stdbool.h>
 #include <stddef.h>
+#include <stdint.h>
 
 #ifdef __cplusplus
 extern "C" {  // only need to export C interface if
@@ -23,6 +24,8 @@ enum LDLogLevel {
     LD_LOG_INFO = 1,
     LD_LOG_WARN = 2,
     LD_LOG_ERROR = 3,
+    LD_UNUSED_MAXVALUE = INT32_MAX /* Used to ensure the underlying type is
+                                    * at least 32 bits. */
 };
 
 /**
@@ -40,7 +43,8 @@ LDLogLevel_Name(enum LDLogLevel level, char const* level_if_unknown);
  * @param level Name of level.
  * @param level_if_unknown Default level to return if the level wasn't
  * recognized.
- * @return LDLogLevel matching the name, or level_if_unknown if not recognized.
+ * @return LDLogLevel matching the name, or level_if_unknown if not
+ * recognized.
  */
 LD_EXPORT(enum LDLogLevel)
 LDLogLevel_Enum(char const* level, enum LDLogLevel level_if_unknown);

libs/common/include/launchdarkly/logging/log_level.hpp

@@ -1,5 +1,6 @@
 #pragma once
 
+#include <cstdint>
 #include <ostream>
 
 namespace launchdarkly {
@@ -8,7 +9,7 @@ namespace launchdarkly {
  * severity. The values must not be changed to ensure backwards compatibility
  * with the C API.
  */
-enum class LogLevel {
+enum class LogLevel : std::int32_t {
     kDebug = 0,
     kInfo = 1,
     kWarn = 2,

libs/common/src/bindings/c/logging/log_level.cpp

@@ -2,6 +2,8 @@
 
 #include <launchdarkly/logging/log_level.hpp>
 
+static_assert(sizeof(LDLogLevel) >= 4, "LDLogLevel must be at least 32 bits");
+
 LD_EXPORT(char const*)
 LDLogLevel_Name(LDLogLevel level, char const* name_if_unknown) {
     return GetLogLevelName(static_cast<launchdarkly::LogLevel>(level),

libs/common/src/log_level.cpp

@@ -11,13 +11,12 @@ char const* GetLogLevelName(LogLevel level, char const* default_) {
             return "debug";
         case LogLevel::kInfo:
             return "info";
-        case LogLevel::kWarn: {
+        case LogLevel::kWarn:
             return "warn";
-            case LogLevel::kError:
-                return "error";
-            default:
-                return default_;
-        }
+        case LogLevel::kError:
+            return "error";
+        default:
+            return default_;
     }
 }
 

libs/common/tests/logging_c_binding_test.cpp

@@ -7,12 +7,11 @@ TEST(LogLevelTests, LogLevelToString) {
     ASSERT_STREQ("info", LDLogLevel_Name(LD_LOG_INFO, "unknown"));
     ASSERT_STREQ("warn", LDLogLevel_Name(LD_LOG_WARN, "unknown"));
     ASSERT_STREQ("error", LDLogLevel_Name(LD_LOG_ERROR, "unknown"));
-    ASSERT_STREQ("unknown",
-                 LDLogLevel_Name(static_cast<LDLogLevel>(4141), "unknown"));
+    ASSERT_STREQ("unknown", LDLogLevel_Name(LD_UNUSED_MAXVALUE, "unknown"));
 }
 
 TEST(LogLevelTests, LogLevelToEnum) {
-    constexpr auto unknown = static_cast<LDLogLevel>(4141);
+    LDLogLevel unknown = LD_UNUSED_MAXVALUE;
     ASSERT_EQ(LD_LOG_DEBUG, LDLogLevel_Enum("debug", unknown));
     ASSERT_EQ(LD_LOG_INFO, LDLogLevel_Enum("info", unknown));
     ASSERT_EQ(LD_LOG_WARN, LDLogLevel_Enum("warn", unknown));