Fix #50 by using nullptr and adding stricter warning.

CMakeLists.txt

@@ -40,6 +40,7 @@ add_cxx_compiler_flag(-Wall)
 add_cxx_compiler_flag(-Wshadow)
 add_cxx_compiler_flag(-Werror)
 add_cxx_compiler_flag(-pedantic-errors)
+add_cxx_compiler_flag(-Wzero-as-null-pointer-constant)
 
 # Release flags
 add_cxx_compiler_flag(-fno-strict-aliasing RELEASE)

cmake/CXXFeatureCheck.cmake

@@ -22,13 +22,18 @@ function(cxx_feature_check FILE)
   string(TOUPPER ${FILE} VAR)
   string(TOUPPER "HAVE_${VAR}" FEATURE)
   message("-- Performing Test ${FEATURE}")
-  try_run(RUN_${FEATURE} COMPILE_${FEATURE} ${CMAKE_BINARY_DIR} ${CMAKE_CURRENT_SOURCE_DIR}/cmake/${FILE}.cpp)
+  try_run(RUN_${FEATURE} COMPILE_${FEATURE}
+          ${CMAKE_BINARY_DIR} ${CMAKE_CURRENT_SOURCE_DIR}/cmake/${FILE}.cpp)
   if(RUN_${FEATURE} EQUAL 0)
-    message("-- Performing Test ${FEATURE} -- Success")
+    message("-- Performing Test ${FEATURE} -- success")
     set(HAVE_${VAR} 1 PARENT_SCOPE)
     add_definitions(-DHAVE_${VAR})
   else()
-    message("-- Performing Test ${FEATURE} -- Failed")
+    if(NOT COMPILE_${FEATURE})
+      message("-- Performing Test ${FEATURE} -- failed to compile")
+    else()
+      message("-- Performing Test ${FEATURE} -- compiled but failed to run")
+    endif()
   endif()
 endfunction()
 

cmake/gnu_posix_regex.cpp

@@ -7,6 +7,6 @@ int main() {
   if (ec != 0) {
     return ec;
   }
-  return regexec(&re, str.c_str(), 0, NULL, 0) ? -1 : 0;
+  return regexec(&re, str.c_str(), 0, nullptr, 0) ? -1 : 0;
 }
 

cmake/posix_regex.cpp

@@ -7,6 +7,6 @@ int main() {
   if (ec != 0) {
     return ec;
   }
-  return regexec(&re, str.c_str(), 0, NULL, 0)  ? -1 : 0;
+  return regexec(&re, str.c_str(), 0, nullptr, 0) ? -1 : 0;
 }
 

cmake/std_regex.cpp

@@ -2,7 +2,9 @@
 #include <string>
 int main() {
   const std::string str = "test0159";
-  const std::regex re("^[a-z]+[0-9]+$", std::regex_constants::extended | std::regex_constants::nosubs);
+  const std::regex re(
+      "^[a-z]+[0-9]+$",
+      std::regex_constants::extended | std::regex_constants::nosubs);
   return std::regex_search(str, re) ? 0 : -1;
 }