Check for nullptr when getting appdata_path

CMakeLists.txt

@@ -1,3 +1,53 @@
+if(NOT CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
+
+# Generated by `boostdep --cmake compute`
+# Copyright 2020, 2021 Peter Dimov
+# Distributed under the Boost Software License, Version 1.0.
+# https://www.boost.org/LICENSE_1_0.txt
+
+cmake_minimum_required(VERSION 3.5...3.20)
+
+project(boost_compute VERSION "${BOOST_SUPERPROJECT_VERSION}" LANGUAGES CXX)
+
+add_library(boost_compute INTERFACE)
+add_library(Boost::compute ALIAS boost_compute)
+
+target_include_directories(boost_compute INTERFACE include)
+
+target_link_libraries(boost_compute
+  INTERFACE
+    Boost::algorithm
+    Boost::array
+    Boost::assert
+    Boost::atomic
+    Boost::chrono
+    Boost::config
+    Boost::core
+    Boost::filesystem
+    Boost::function
+    Boost::function_types
+    Boost::fusion
+    Boost::iterator
+    Boost::lexical_cast
+    Boost::mpl
+    Boost::optional
+    Boost::preprocessor
+    Boost::property_tree
+    Boost::proto
+    Boost::range
+    Boost::smart_ptr
+    Boost::static_assert
+    Boost::thread
+    Boost::throw_exception
+    Boost::tuple
+    Boost::type_traits
+    Boost::typeof
+    Boost::utility
+    Boost::uuid
+)
+
+else()
+
 # ---------------------------------------------------------------------------
 #  Copyright (c) 2013 Kyle Lutz <[email protected]>
 #
@@ -127,3 +177,5 @@ install(
 
 # install header files
 install(DIRECTORY include/boost DESTINATION include/compute)
+
+endif()

include/boost/compute/detail/path.hpp

@@ -30,13 +30,20 @@ static const std::string& path_delim()
 // Path to appdata folder.
 inline const std::string& appdata_path()
 {
+    const char *user_path;
     #ifdef _WIN32
-    static const std::string appdata = detail::getenv("APPDATA")
-        + path_delim() + "boost_compute";
+    user_path = detail::getenv("APPDATA");
+    if (user_path == nullptr) {
+        std::cerr << "ERROR: Unable to find APPDATA environment variable." << std::endl;
+    }
     #else
-    static const std::string appdata = detail::getenv("HOME")
-        + path_delim() + ".boost_compute";
+    user_path = detail::getenv("HOME");
+    if (user_path == nullptr) {
+        std::cerr << "ERROR: Unable to find HOME environment variable." << std::endl;
+    }
     #endif
+    static const std::string appdata = user_path
+        + path_delim() + ".boost_compute";
     return appdata;
 }