fixup

Author: JGRennison

src/string.cpp

@@ -1400,16 +1400,17 @@ const char *StrErrorDumper::Get(int errornum)
 		return this->buf;
 	}
 #else
+	struct StrErrorRHelper {
+		static bool Success(char *result) { return true; }      ///< GNU-specific
+		static bool Success(int result) { return result == 0; } ///< XSI-compliant
+
+		static const char *GetString(char *result, const char *buffer) { return result; } ///< GNU-specific
+		static const char *GetString(int result, const char *buffer) { return buffer; }   ///< XSI-compliant
+	};
+
 	auto result = strerror_r(errornum, this->buf, lengthof(this->buf));
-	static_assert(std::is_same_v<decltype(result), char *> || std::is_same_v<decltype(result), int>);
-	if constexpr (std::is_same_v<decltype(result), char *>) {
-		/* GNU-specific */
-		return result;
-	} else {
-		/* XSI-compliant */
-		if (result == 0) {
-			return this->buf;
-		}
+	if (StrErrorRHelper::Success(result)) {
+		return StrErrorRHelper::GetString(result, this->buf);
 	}
 #endif