correct warning flags on gcc/clang and msvc. fix bug in appleclang

Author: me

tests/CMakeLists.txt

@@ -1,6 +1,10 @@
 cmake_minimum_required(VERSION 3.13)
 project(MsgPackTests)
 
+# Helpers
+set(IS_MSVC       "$<CXX_COMPILER_ID:MSVC>")
+set(IS_NOT_MSVC   "$<NOT:${IS_MSVC}>")
+
 # Deps
 include(FetchContent)
 
@@ -29,6 +33,7 @@ add_executable(tests
   value.cpp
   pack.cpp)
 target_compile_features(tests PRIVATE cxx_std_17)
-target_compile_options(tests PRIVATE -Wall -Wextra)
+target_compile_options(tests PRIVATE $<${IS_NOT_MSVC}:-Wall -Wextra -Wpedantic -Werror>)
+target_compile_options(tests PRIVATE $<${IS_MSVC}:/Wall /WX>)
 target_include_directories(tests PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/../src)
 target_link_libraries(tests  PRIVATE Boost::describe PRIVATE msgpack-cxx)

tests/pack.cpp

@@ -242,7 +242,7 @@ TEST_SUITE("[PACK]")
                                 "might refuse to come. What could he do then? Every moment was of vital"
                                 "importance.";
         std::string o(70000, 0);
-        std::generate(begin(o), end(o), [&]{return std::uniform_int_distribution<char>{}(eng);});
+        std::generate(begin(o), end(o), [&]{return std::uniform_int_distribution<int>{std::numeric_limits<char>::min(), std::numeric_limits<char>::max()}(eng);});
 
         std::vector<char>    p(255);
         std::vector<uint8_t> q(255);