imports: Switch to Microsoft GSL implementation

... with two minor code base changes compared to previous
use of gsl-lite:

- dag.hpp: ActionNode::Ptr and ArtifactNode::Ptr are not
  wrapped in gsl::not_null<> anymore, due to lack of support
  for wrapping std::unique_ptr<>. More specifically, the
  move constructor is missing, rendering it impossible to
  use std::vector<>::emplace_back().

- utils/cpp/gsl.hpp: New header file added to implement the
  macros ExpectsAudit() and EnsureAudit(), asserts running
  only in debug builds, which were available in gsl-lite but
  are missing in MS GSL.

6 files changed, 17 insertions, 21 deletions

diff --git a/src/buildtool/multithreading/TARGETS b/src/buildtool/multithreading/TARGETS
index 2e5467f4..2d758589 100644
--- a/src/buildtool/multithreading/TARGETS
+++ b/src/buildtool/multithreading/TARGETS
@@ -9,8 +9,7 @@
   { "type": ["@", "rules", "CC", "library"]
   , "name": ["notification_queue"]
   , "hdrs": ["notification_queue.hpp"]
-  , "deps":
-    ["task", ["src/utils/cpp", "atomic"], ["@", "gsl-lite", "", "gsl-lite"]]
+  , "deps": ["task", ["src/utils/cpp", "atomic"], ["@", "gsl", "", "gsl"]]
   , "stage": ["src", "buildtool", "multithreading"]
   }
 , "task_system":
@@ -18,7 +17,7 @@
   , "name": ["task_system"]
   , "hdrs": ["task_system.hpp"]
   , "srcs": ["task_system.cpp"]
-  , "deps": ["notification_queue", ["@", "gsl-lite", "", "gsl-lite"]]
+  , "deps": ["notification_queue", ["@", "gsl", "", "gsl"]]
   , "stage": ["src", "buildtool", "multithreading"]
   , "private-deps": ["task"]
   }
@@ -26,19 +25,15 @@
   { "type": ["@", "rules", "CC", "library"]
   , "name": ["async_map_node"]
   , "hdrs": ["async_map_node.hpp"]
-  , "deps": ["task", "task_system", ["@", "gsl-lite", "", "gsl-lite"]]
+  , "deps":
+    ["task", "task_system", ["src/utils/cpp", "gsl"], ["@", "gsl", "", "gsl"]]
   , "stage": ["src", "buildtool", "multithreading"]
   }
 , "async_map":
   { "type": ["@", "rules", "CC", "library"]
   , "name": ["async_map"]
   , "hdrs": ["async_map.hpp"]
-  , "deps":
-    [ "task"
-    , "task_system"
-    , "async_map_node"
-    , ["@", "gsl-lite", "", "gsl-lite"]
-    ]
+  , "deps": ["task", "task_system", "async_map_node", ["@", "gsl", "", "gsl"]]
   , "stage": ["src", "buildtool", "multithreading"]
   }
 , "async_map_consumer":
@@ -50,7 +45,7 @@
     , "task_system"
     , "async_map_node"
     , "async_map"
-    , ["@", "gsl-lite", "", "gsl-lite"]
+    , ["@", "gsl", "", "gsl"]
     ]
   , "stage": ["src", "buildtool", "multithreading"]
   }
diff --git a/src/buildtool/multithreading/async_map.hpp b/src/buildtool/multithreading/async_map.hpp
index 91ffd8c2..3267b312 100644
--- a/src/buildtool/multithreading/async_map.hpp
+++ b/src/buildtool/multithreading/async_map.hpp
@@ -23,7 +23,7 @@
 #include <utility>  // std::make_pair to use std::unordered_map's emplace()
 #include <vector>
 
-#include "gsl-lite/gsl-lite.hpp"
+#include "gsl/gsl"
 #include "src/buildtool/multithreading/async_map_node.hpp"
 #include "src/buildtool/multithreading/task.hpp"
 #include "src/buildtool/multithreading/task_system.hpp"
diff --git a/src/buildtool/multithreading/async_map_consumer.hpp b/src/buildtool/multithreading/async_map_consumer.hpp
index 3dcc0eff..0de6b36f 100644
--- a/src/buildtool/multithreading/async_map_consumer.hpp
+++ b/src/buildtool/multithreading/async_map_consumer.hpp
@@ -25,7 +25,7 @@
 #include <unordered_set>
 #include <vector>
 
-#include "gsl-lite/gsl-lite.hpp"
+#include "gsl/gsl"
 #include "src/buildtool/multithreading/async_map.hpp"
 #include "src/buildtool/multithreading/async_map_node.hpp"
 #include "src/buildtool/multithreading/task.hpp"
diff --git a/src/buildtool/multithreading/async_map_node.hpp b/src/buildtool/multithreading/async_map_node.hpp
index c729582d..2c07f11b 100644
--- a/src/buildtool/multithreading/async_map_node.hpp
+++ b/src/buildtool/multithreading/async_map_node.hpp
@@ -19,9 +19,10 @@
 #include <mutex>
 #include <optional>
 
-#include "gsl-lite/gsl-lite.hpp"
+#include "gsl/gsl"
 #include "src/buildtool/multithreading/task.hpp"
 #include "src/buildtool/multithreading/task_system.hpp"
+#include "src/utils/cpp/gsl.hpp"
 
 // Wrapper around Value to enable async access to it in a continuation-style
 // programming way
@@ -154,7 +155,7 @@ class AsyncMapNode {
     // Not thread safe, do not use unless the value has been already set
     [[nodiscard]] auto GetValue() const& noexcept -> Value const& {
         // Will only be checked in debug build
-        gsl_ExpectsAudit(value_.has_value());
+        ExpectsAudit(value_.has_value());
         return *value_;
     }
     [[nodiscard]] auto GetValue() && noexcept = delete;
diff --git a/src/buildtool/multithreading/notification_queue.hpp b/src/buildtool/multithreading/notification_queue.hpp
index 1df5d659..9d2f06eb 100644
--- a/src/buildtool/multithreading/notification_queue.hpp
+++ b/src/buildtool/multithreading/notification_queue.hpp
@@ -22,7 +22,7 @@
 #include <shared_mutex>
 #include <utility>  // std::forward
 
-#include "gsl-lite/gsl-lite.hpp"
+#include "gsl/gsl"
 #include "src/buildtool/multithreading/task.hpp"
 #include "src/utils/cpp/atomic.hpp"
 
@@ -67,14 +67,14 @@ class WaitableZeroCounter {
 class NotificationQueue {
   public:
     explicit NotificationQueue(
-        gsl::not_null<WaitableZeroCounter*> total_workload)
-        : total_workload_{std::move(total_workload)} {}
+        gsl::not_null<WaitableZeroCounter*> const& total_workload)
+        : total_workload_{total_workload} {}
 
     NotificationQueue(NotificationQueue const& other) = delete;
     NotificationQueue(NotificationQueue&& other) noexcept
         : queue_{std::move(other.queue_)},
           done_{other.done_},
-          total_workload_{std::move(other.total_workload_)} {}
+          total_workload_{other.total_workload_} {}
     ~NotificationQueue() = default;
 
     [[nodiscard]] auto operator=(NotificationQueue const& other)
diff --git a/src/buildtool/multithreading/task_system.cpp b/src/buildtool/multithreading/task_system.cpp
index cf9ed543..13c3caec 100644
--- a/src/buildtool/multithreading/task_system.cpp
+++ b/src/buildtool/multithreading/task_system.cpp
@@ -14,7 +14,7 @@
 
 #include "src/buildtool/multithreading/task_system.hpp"
 
-#include "gsl-lite/gsl-lite.hpp"
+#include "gsl/gsl"
 #include "src/buildtool/multithreading/task.hpp"
 
 TaskSystem::TaskSystem() : TaskSystem(std::thread::hardware_concurrency()) {}
@@ -59,7 +59,7 @@ void TaskSystem::Finish() noexcept {
 }
 
 void TaskSystem::Run(std::size_t idx) {
-    gsl_Expects(thread_count_ > 0);
+    Expects(thread_count_ > 0);
 
     while (not shutdown_) {
         std::optional<Task> t{};